Reflective programming

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Historical background

The earliest computers were programmed in their native assembly languages, which were inherently reflective, as these original architectures could be programmed by defining instructions as data and using self-modifying code. As the bulk of programming moved to higher-level compiled languages such as ALGOL, COBOL, Fortran, Pascal, and C, this reflective ability largely disappeared until new programming languages with reflection built into their type systems appeared.

Brian Cantwell Smith's 1982 doctoral dissertation introduced the notion of computational reflection in procedural programming languages and the notion of the meta-circular interpreter as a component of 3-Lisp.

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Uses

Reflection helps programmers make generic software libraries to display data, process different formats of data, perform serialization and deserialization of data for communication, or do bundling and unbundling of data for containers or bursts of communication. Reflective systems may provide a mirror type, used as a decoupled reflection of an object or identifier.

Effective use of reflection almost always requires a plan: A design framework, encoding description, object library, a map of a database or entity relations.

Reflection makes a language more suited to network-oriented code. For example, it assists languages such as Java to operate well in networks by enabling libraries for serialization, bundling and varying data formats. Languages without reflection such as C are required to use auxiliary compilers for tasks like Abstract Syntax Notation (ASN.1) to produce code for serialization and bundling.

Reflection can be used for observing and modifying program execution at runtime. A reflection-oriented program component can monitor the execution of an enclosure of code and can modify itself according to a desired goal of that enclosure. This is typically accomplished by dynamically assigning program code at runtime.

In object-oriented programming languages such as Java, reflection allows inspection of classes, interfaces, fields, and methods at runtime without knowing the names of the interfaces, fields, methods at compile time. It also allows instantiation of new objects and invocation of methods.

Reflection is often used as part of software testing, such as for the runtime creation/instantiation of mock objects.

Reflection is also a key strategy for metaprogramming.

In some object-oriented programming languages such as C# and Java, reflection can be used to bypass member accessibility rules. For C#-properties this can be achieved by writing directly onto the (usually invisible) backing field of a non-public property. It is also possible to find non-public methods of classes and types and manually invoke them. This works for project-internal files as well as external libraries such as .NET's assemblies and Java's archives.

Implementation

A language that supports reflection provides a number of features available at runtime that would otherwise be difficult to accomplish in a lower-level language. Some of these features are the abilities to:

Discover and modify source code constructions (such as code blocks, classes, methods, protocols, etc.) as first-class objects at runtime. Readable object metadata is provided as a mirror.
Convert a string matching the symbolic name of a class or function into a reference to or invocation of that class or function.
Evaluate a string as if it were a source-code statement at runtime.
Create a new interpreter for the language's bytecode to give a new meaning or purpose for a programming construct.

These features can be implemented in different ways. In MOO, reflection forms a natural part of everyday programming idiom. When verbs (methods) are called, various variables such as verb (the name of the verb being called) and this (the object on which the verb is called) are populated to give the context of the call. Security is typically managed by accessing the caller stack programmatically: Since callers() is a list of the methods by which the current verb was eventually called, performing tests on callers()[0] (the command invoked by the original user) allows the verb to protect itself against unauthorised use.

Compiled languages rely on their runtime system to provide information about the source code. A compiled Objective-C executable, for example, records the names of all methods in a block of the executable, providing a table to correspond these with the underlying methods (or selectors for these methods) compiled into the program. In a compiled language that supports runtime creation of functions, such as Common Lisp, the runtime environment must include a compiler or an interpreter.

Reflection can be implemented for languages without built-in reflection by using a program transformation system to define automated source-code changes.

Security considerations

Reflection may allow a user to create unexpected control flow paths through an application, potentially bypassing security measures. This may be exploited by attackers. Historical vulnerabilities in Java caused by unsafe reflection allowed code retrieved from potentially untrusted remote machines to break out of the Java sandbox security mechanism. A large scale study of 120 Java vulnerabilities in 2013 concluded that unsafe reflection is the most common vulnerability in Java, though not the most exploited.

Runtime performance

Runtime reflection systems introduce a non-negligible runtime performance overhead. For instance, in Java, because reflective operations are resolved dynamically at execution time, many compiler and JVM optimizations—such as method inlining, static binding, and aggressive just-in-time specialization—cannot be fully applied. As a consequence, reflective calls are typically slower than their statically resolved counterparts. Microbenchmark and application-level studies on Java have shown that reflective operations can incur substantial runtime overhead, especially for method invocation and dynamic object creation, with slowdowns ranging from around 20–40% in moderate cases to more than 300× in heavily reflective dispatch scenarios. In sequential applications, reflection can significantly increase execution time and memory consumption when used in performance-critical code paths. In multithreaded applications, reflective implementations generally preserve scalability, but still exhibit noticeably higher absolute execution times—commonly between 1.5x and 10× slower—than equivalent non-reflective code.

In languages like C++ and Rust, reflection is performed at compile time. Compile-time reflection systems are weaker than runtime reflection systems like those of Java and C#, but incur no runtime overhead due to being performed during compilation.

Examples

The following code snippets create an instance foo of class Foo and invoke its method PrintHello. For each programming language, normal and reflection-based call sequences are shown.

Common Lisp

The example below is in Common Lisp using the Common Lisp Object System:

<span id="mwqw"></span><span class="p" id="mwrA">(</span><span class="nb" id="mwrQ">defclass</span><span class="w" id="mwrg"> </span><span class="nv" id="mwrw">foo</span><span class="w" id="mwsA"> </span><span class="p" id="mwsQ">()</span><span class="w" id="mwsg"> </span><span class="p" id="mwsw">())</span> <span class="p" id="mwtA">(</span><span class="nb" id="mwtQ">defmethod</span><span class="w" id="mwtg"> </span><span class="nv" id="mwtw">print-hello</span><span class="w" id="mwuA"> </span><span class="p" id="mwuQ">((</span><span class="nv" id="mwug">f</span><span class="w" id="mwuw"> </span><span class="nv" id="mwvA">foo</span><span class="p" id="mwvQ">))</span><span class="w" id="mwvg"> </span><span class="p" id="mwvw">(</span><span class="nb" id="mwwA">format</span><span class="w" id="mwwQ"> </span><span class="no" id="mwwg">T</span><span class="w" id="mwww"> </span><span class="s" id="mwxA">"Hello from ~S~%"</span><span class="w" id="mwxQ"> </span><span class="nv" id="mwxg">f</span><span class="p" id="mwxw">))</span> <span class="c1" id="mwyA">;; Normal, without reflection</span> <span class="p" id="mwyQ">(</span><span class="k" id="mwyg">let</span><span class="w" id="mwyw"> </span><span class="p" id="mwzA">((</span><span class="nv" id="mwzQ">foo</span><span class="w" id="mwzg"> </span><span class="p" id="mwzw">(</span><span class="nb" id="mw0A">make-instance</span><span class="w" id="mw0Q"> </span><span class="ss" id="mw0g">'foo</span><span class="p" id="mw0w">)))</span> <span class="w" id="mw1A"> </span><span class="p" id="mw1Q">(</span><span class="nv" id="mw1g">print-hello</span><span class="w" id="mw1w"> </span><span class="nv" id="mw2A">foo</span><span class="p" id="mw2Q">))</span> <span class="c1" id="mw2g">;; With reflection to look up the class named "foo" and the method</span> <span class="c1" id="mw2w">;; named "print-hello" that specializes on "foo".</span> <span class="p" id="mw3A">(</span><span class="k" id="mw3Q">let*</span><span class="w" id="mw3g"> </span><span class="p" id="mw3w">((</span><span class="nv" id="mw4A">foo-class</span><span class="w" id="mw4Q"> </span><span class="p" id="mw4g">(</span><span class="nb" id="mw4w">find-class</span><span class="w" id="mw5A"> </span><span class="p" id="mw5Q">(</span><span class="nb" id="mw5g">read-from-string</span><span class="w" id="mw5w"> </span><span class="s" id="mw6A">"foo"</span><span class="p" id="mw6Q">)))</span> <span class="w" id="mw6g"> </span><span class="p" id="mw6w">(</span><span class="nv" id="mw7A">print-hello-method</span><span class="w" id="mw7Q"> </span><span class="p" id="mw7g">(</span><span class="nb" id="mw7w">find-method</span><span class="w" id="mw8A"> </span><span class="p" id="mw8Q">(</span><span class="nb" id="mw8g">symbol-function</span><span class="w" id="mw8w"> </span><span class="p" id="mw9A">(</span><span class="nb" id="mw9Q">read-from-string</span><span class="w" id="mw9g"> </span><span class="s" id="mw9w">"print-hello"</span><span class="p" id="mw-A">))</span> <span class="w" id="mw-Q"> </span><span class="no" id="mw-g">nil</span><span class="w" id="mw-w"> </span><span class="p" id="mw_A">(</span><span class="nb" id="mw_Q">list</span><span class="w" id="mw_g"> </span><span class="nv" id="mw_w">foo-class</span><span class="p" id="mwAQA">))))</span> <span class="w" id="mwAQE"> </span><span class="p" id="mwAQI">(</span><span class="nb" id="mwAQM">funcall</span><span class="w" id="mwAQQ"> </span><span class="p" id="mwAQU">(</span><span class="nv" id="mwAQY">sb-mop:method-generic-function</span><span class="w" id="mwAQc"> </span><span class="nv" id="mwAQg">print-hello-method</span><span class="p" id="mwAQk">)</span> <span class="w" id="mwAQo"> </span><span class="p" id="mwAQs">(</span><span class="nb" id="mwAQw">make-instance</span><span class="w" id="mwAQ0"> </span><span class="nv" id="mwAQ4">foo-class</span><span class="p" id="mwAQ8">)))</span>

C

Reflection is not possible in C, though parts of reflection can be emulated.

<span id="mwARU"></span><span class="cp" id="mwARY">#include</span><span class="w" id="mwARc"> </span><span class="cpf" id="mwARg"><stdio.h></span> <span class="cp" id="mwARk">#include</span><span class="w" id="mwARo"> </span><span class="cpf" id="mwARs"><stdlib.h></span> <span class="cp" id="mwARw">#include</span><span class="w" id="mwAR0"> </span><span class="cpf" id="mwAR4"><string.h></span> <span class="k" id="mwAR8">typedef</span><span class="w" id="mwASA"> </span><span class="k" id="mwASE">struct</span><span class="w" id="mwASI"> </span><span class="p" id="mwASM">{</span> <span class="w" id="mwASQ"> </span><span class="c1" id="mwASU">// ...</span> <span class="p" id="mwASY">}</span><span class="w" id="mwASc"> </span><span class="n" id="mwASg">Foo</span><span class="p" id="mwASk">;</span> <span class="k" id="mwASo">typedef</span><span class="w" id="mwASs"> </span><span class="kt" id="mwASw">void</span><span class="w" id="mwAS0"> </span><span class="p" id="mwAS4">(</span><span class="o" id="mwAS8">*</span><span class="n" id="mwATA">Method</span><span class="p" id="mwATE">)(</span><span class="kt" id="mwATI">void</span><span class="o" id="mwATM">*</span><span class="p" id="mwATQ">);</span> <span class="c1" id="mwATU">// The method: Foo::printHello</span> <span class="kt" id="mwATY">void</span><span class="w" id="mwATc"> </span><span class="nf" id="mwATg">Foo_printHello</span><span class="p" id="mwATk">(</span><span class="kt" id="mwATo">void</span><span class="o" id="mwATs">*</span><span class="w" id="mwATw"> </span><span class="n" id="mwAT0">_</span><span class="p" id="mwAT4">)</span><span class="w" id="mwAT8"> </span><span class="p" id="mwAUA">{</span> <span class="w" id="mwAUE"> </span><span class="n" id="mwAUI">printf</span><span class="p" id="mwAUM">(</span><span class="s" id="mwAUQ">"Hello, world!</span><span class="se" id="mwAUU">\n</span><span class="s" id="mwAUY">"</span><span class="p" id="mwAUc">);</span> <span class="p" id="mwAUg">}</span> <span class="c1" id="mwAUk">// Simulated method table</span> <span class="k" id="mwAUo">typedef</span><span class="w" id="mwAUs"> </span><span class="k" id="mwAUw">struct</span><span class="w" id="mwAU0"> </span><span class="p" id="mwAU4">{</span> <span class="w" id="mwAU8"> </span><span class="k" id="mwAVA">const</span><span class="w" id="mwAVE"> </span><span class="kt" id="mwAVI">char</span><span class="o" id="mwAVM">*</span><span class="w" id="mwAVQ"> </span><span class="n" id="mwAVU">name</span><span class="p" id="mwAVY">;</span> <span class="w" id="mwAVc"> </span><span class="n" id="mwAVg">Method</span><span class="w" id="mwAVk"> </span><span class="n" id="mwAVo">fn</span><span class="p" id="mwAVs">;</span> <span class="p" id="mwAVw">}</span><span class="w" id="mwAV0"> </span><span class="n" id="mwAV4">MethodEntry</span><span class="p" id="mwAV8">;</span> <span class="k" id="mwAWA">const</span><span class="w" id="mwAWE"> </span><span class="n" id="mwAWI">MethodEntry</span><span class="w" id="mwAWM"> </span><span class="n" id="mwAWQ">FOO_METHODS</span><span class="p" id="mwAWU">[]</span><span class="w" id="mwAWY"> </span><span class="o" id="mwAWc">=</span><span class="w" id="mwAWg"> </span><span class="p" id="mwAWk">{</span> <span class="w" id="mwAWo"> </span><span class="p" id="mwAWs">{</span><span class="w" id="mwAWw"> </span><span class="s" id="mwAW0">"printHello"</span><span class="p" id="mwAW4">,</span><span class="w" id="mwAW8"> </span><span class="n" id="mwAXA">Foo_printHello</span><span class="w" id="mwAXE"> </span><span class="p" id="mwAXI">},</span> <span class="w" id="mwAXM"> </span><span class="p" id="mwAXQ">{</span><span class="w" id="mwAXU"> </span><span class="nb" id="mwAXY">NULL</span><span class="p" id="mwAXc">,</span><span class="w" id="mwAXg"> </span><span class="nb" id="mwAXk">NULL</span><span class="w" id="mwAXo"> </span><span class="p" id="mwAXs">}</span><span class="w" id="mwAXw"> </span><span class="c1" id="mwAX0">// Sentinel to mark end</span> <span class="p" id="mwAX4">};</span> <span class="c1" id="mwAX8">// Simulate reflective method lookup</span> <span class="n" id="mwAYA">Method</span><span class="w" id="mwAYE"> </span><span class="nf" id="mwAYI">findMethodByName</span><span class="p" id="mwAYM">(</span><span class="k" id="mwAYQ">const</span><span class="w" id="mwAYU"> </span><span class="kt" id="mwAYY">char</span><span class="o" id="mwAYc">*</span><span class="w" id="mwAYg"> </span><span class="n" id="mwAYk">name</span><span class="p" id="mwAYo">)</span><span class="w" id="mwAYs"> </span><span class="p" id="mwAYw">{</span> <span class="w" id="mwAY0"> </span><span class="k" id="mwAY4">for</span><span class="w" id="mwAY8"> </span><span class="p" id="mwAZA">(</span><span class="kt" id="mwAZE">size_t</span><span class="w" id="mwAZI"> </span><span class="n" id="mwAZM">i</span><span class="w" id="mwAZQ"> </span><span class="o" id="mwAZU">=</span><span class="w" id="mwAZY"> </span><span class="mi" id="mwAZc">0</span><span class="p" id="mwAZg">;</span><span class="w" id="mwAZk"> </span><span class="n" id="mwAZo">FOO_METHODS</span><span class="p" id="mwAZs">[</span><span class="n" id="mwAZw">i</span><span class="p" id="mwAZ0">].</span><span class="n" id="mwAZ4">name</span><span class="p" id="mwAZ8">;</span><span class="w" id="mwAaA"> </span><span class="n" id="mwAaE">i</span><span class="o" id="mwAaI">++</span><span class="p" id="mwAaM">)</span><span class="w" id="mwAaQ"> </span><span class="p" id="mwAaU">{</span> <span class="w" id="mwAaY"> </span><span class="k" id="mwAac">if</span><span class="w" id="mwAag"> </span><span class="p" id="mwAak">(</span><span class="n" id="mwAao">strcmp</span><span class="p" id="mwAas">(</span><span class="n" id="mwAaw">FOO_METHODS</span><span class="p" id="mwAa0">[</span><span class="n" id="mwAa4">i</span><span class="p" id="mwAa8">].</span><span class="n" id="mwAbA">name</span><span class="p" id="mwAbE">,</span><span class="w" id="mwAbI"> </span><span class="n" id="mwAbM">name</span><span class="p" id="mwAbQ">)</span><span class="w" id="mwAbU"> </span><span class="o" id="mwAbY">==</span><span class="w" id="mwAbc"> </span><span class="mi" id="mwAbg">0</span><span class="p" id="mwAbk">)</span><span class="w" id="mwAbo"> </span><span class="p" id="mwAbs">{</span> <span class="w" id="mwAbw"> </span><span class="k" id="mwAb0">return</span><span class="w" id="mwAb4"> </span><span class="n" id="mwAb8">FOO_METHODS</span><span class="p" id="mwAcA">[</span><span class="n" id="mwAcE">i</span><span class="p" id="mwAcI">].</span><span class="n" id="mwAcM">fn</span><span class="p" id="mwAcQ">;</span> <span class="w" id="mwAcU"> </span><span class="p" id="mwAcY">}</span> <span class="w" id="mwAcc"> </span><span class="p" id="mwAcg">}</span> <span class="w" id="mwAck"> </span><span class="k" id="mwAco">return</span><span class="w" id="mwAcs"> </span><span class="nb" id="mwAcw">NULL</span><span class="p" id="mwAc0">;</span> <span class="p" id="mwAc4">}</span> <span class="kt" id="mwAc8">int</span><span class="w" id="mwAdA"> </span><span class="nf" id="mwAdE">main</span><span class="p" id="mwAdI">()</span><span class="w" id="mwAdM"> </span><span class="p" id="mwAdQ">{</span> <span class="w" id="mwAdU"> </span><span class="c1" id="mwAdY">// Without reflection</span> <span class="w" id="mwAdc"> </span><span class="n" id="mwAdg">Foo</span><span class="w" id="mwAdk"> </span><span class="n" id="mwAdo">foo</span><span class="p" id="mwAds">;</span> <span class="w" id="mwAdw"> </span><span class="n" id="mwAd0">Foo_printHello</span><span class="p" id="mwAd4">(</span><span class="o" id="mwAd8">&</span><span class="n" id="mwAeA">foo</span><span class="p" id="mwAeE">);</span> <span class="w" id="mwAeI"> </span><span class="c1" id="mwAeM">// With emulated reflection</span> <span class="w" id="mwAeQ"> </span><span class="n" id="mwAeU">Foo</span><span class="o" id="mwAeY">*</span><span class="w" id="mwAec"> </span><span class="n" id="mwAeg">reflected</span><span class="w" id="mwAek"> </span><span class="o" id="mwAeo">=</span><span class="w" id="mwAes"> </span><span class="p" id="mwAew">(</span><span class="n" id="mwAe0">Foo</span><span class="o" id="mwAe4">*</span><span class="p" id="mwAe8">)</span><span class="n" id="mwAfA">malloc</span><span class="p" id="mwAfE">(</span><span class="k" id="mwAfI">sizeof</span><span class="p" id="mwAfM">(</span><span class="n" id="mwAfQ">Foo</span><span class="p" id="mwAfU">));</span> <span class="w" id="mwAfY"> </span><span class="k" id="mwAfc">if</span><span class="w" id="mwAfg"> </span><span class="p" id="mwAfk">(</span><span class="o" id="mwAfo">!</span><span class="n" id="mwAfs">reflected</span><span class="p" id="mwAfw">)</span><span class="w" id="mwAf0"> </span><span class="p" id="mwAf4">{</span> <span class="w" id="mwAf8"> </span><span class="n" id="mwAgA">fprintf</span><span class="p" id="mwAgE">(</span><span class="n" id="mwAgI">stderr</span><span class="p" id="mwAgM">,</span><span class="w" id="mwAgQ"> </span><span class="s" id="mwAgU">"Memory allocation failed</span><span class="se" id="mwAgY">\n</span><span class="s" id="mwAgc">"</span><span class="p" id="mwAgg">);</span> <span class="w" id="mwAgk"> </span><span class="k" id="mwAgo">return</span><span class="w" id="mwAgs"> </span><span class="n" id="mwAgw">EXIT_FAILURE</span><span class="p" id="mwAg0">;</span> <span class="w" id="mwAg4"> </span><span class="p" id="mwAg8">}</span> <span class="w" id="mwAhA"> </span><span class="k" id="mwAhE">const</span><span class="w" id="mwAhI"> </span><span class="kt" id="mwAhM">char</span><span class="o" id="mwAhQ">*</span><span class="w" id="mwAhU"> </span><span class="n" id="mwAhY">name</span><span class="w" id="mwAhc"> </span><span class="o" id="mwAhg">=</span><span class="w" id="mwAhk"> </span><span class="s" id="mwAho">"printHello"</span><span class="p" id="mwAhs">;</span> <span class="w" id="mwAhw"> </span><span class="n" id="mwAh0">Method</span><span class="w" id="mwAh4"> </span><span class="n" id="mwAh8">m</span><span class="w" id="mwAiA"> </span><span class="o" id="mwAiE">=</span><span class="w" id="mwAiI"> </span><span class="n" id="mwAiM">findMethodByName</span><span class="p" id="mwAiQ">(</span><span class="n" id="mwAiU">name</span><span class="p" id="mwAiY">);</span> <span class="w" id="mwAic"> </span><span class="k" id="mwAig">if</span><span class="w" id="mwAik"> </span><span class="p" id="mwAio">(</span><span class="n" id="mwAis">m</span><span class="p" id="mwAiw">)</span><span class="w" id="mwAi0"> </span><span class="p" id="mwAi4">{</span> <span class="w" id="mwAi8"> </span><span class="n" id="mwAjA">m</span><span class="p" id="mwAjE">(</span><span class="n" id="mwAjI">reflected</span><span class="p" id="mwAjM">);</span> <span class="w" id="mwAjQ"> </span><span class="p" id="mwAjU">}</span><span class="w" id="mwAjY"> </span><span class="k" id="mwAjc">else</span><span class="w" id="mwAjg"> </span><span class="p" id="mwAjk">{</span> <span class="w" id="mwAjo"> </span><span class="n" id="mwAjs">fprintf</span><span class="p" id="mwAjw">(</span><span class="n" id="mwAj0">stderr</span><span class="p" id="mwAj4">,</span><span class="w" id="mwAj8"> </span><span class="s" id="mwAkA">"Method '%s' not found</span><span class="se" id="mwAkE">\n</span><span class="s" id="mwAkI">"</span><span class="p" id="mwAkM">,</span><span class="w" id="mwAkQ"> </span><span class="n" id="mwAkU">name</span><span class="p" id="mwAkY">);</span> <span class="w" id="mwAkc"> </span><span class="n" id="mwAkg">free</span><span class="p" id="mwAkk">(</span><span class="n" id="mwAko">reflected</span><span class="p" id="mwAks">);</span> <span class="w" id="mwAkw"> </span><span class="k" id="mwAk0">return</span><span class="w" id="mwAk4"> </span><span class="n" id="mwAk8">EXIT_FAILURE</span><span class="p" id="mwAlA">;</span> <span class="w" id="mwAlE"> </span><span class="p" id="mwAlI">}</span> <span class="w" id="mwAlM"> </span><span class="n" id="mwAlQ">free</span><span class="p" id="mwAlU">(</span><span class="n" id="mwAlY">reflected</span><span class="p" id="mwAlc">);</span> <span class="w" id="mwAlg"> </span><span class="k" id="mwAlk">return</span><span class="w" id="mwAlo"> </span><span class="n" id="mwAls">EXIT_SUCCESS</span><span class="p" id="mwAlw">;</span> <span class="p" id="mwAl0">}</span>

C++

The example below is in C++ (using reflection added in C++26).

<span id="mwAmk"></span><span class="k" id="mwAmo">import</span><span class="w" id="mwAms"> </span><span class="n" id="mwAmw">std</span><span class="p" id="mwAm0">;</span> <span class="k" id="mwAm4">using</span><span class="w" id="mwAm8"> </span><span class="n" id="mwAnA">std</span><span class="o" id="mwAnE">::</span><span class="n" id="mwAnI">string_view</span><span class="p" id="mwAnM">;</span> <span class="k" id="mwAnQ">using</span><span class="w" id="mwAnU"> </span><span class="n" id="mwAnY">std</span><span class="o" id="mwAnc">::</span><span class="n" id="mwAng">views</span><span class="o" id="mwAnk">::</span><span class="n" id="mwAno">filter</span><span class="p" id="mwAns">;</span> <span class="k" id="mwAnw">using</span><span class="w" id="mwAn0"> </span><span class="n" id="mwAn4">std</span><span class="o" id="mwAn8">::</span><span class="n" id="mwAoA">meta</span><span class="o" id="mwAoE">::</span><span class="n" id="mwAoI">access_context</span><span class="p" id="mwAoM">;</span> <span class="k" id="mwAoQ">using</span><span class="w" id="mwAoU"> </span><span class="n" id="mwAoY">std</span><span class="o" id="mwAoc">::</span><span class="n" id="mwAog">meta</span><span class="o" id="mwAok">::</span><span class="n" id="mwAoo">exception</span><span class="p" id="mwAos">;</span> <span class="k" id="mwAow">using</span><span class="w" id="mwAo0"> </span><span class="n" id="mwAo4">std</span><span class="o" id="mwAo8">::</span><span class="n" id="mwApA">meta</span><span class="o" id="mwApE">::</span><span class="n" id="mwApI">info</span><span class="p" id="mwApM">;</span> <span class="k" id="mwApQ">namespace</span><span class="w" id="mwApU"> </span><span class="nn" id="mwApY">meta</span><span class="w" id="mwApc"> </span><span class="o" id="mwApg">=</span><span class="w" id="mwApk"> </span><span class="nn" id="mwApo">std</span><span class="o" id="mwAps">::</span><span class="nn" id="mwApw">meta</span><span class="p" id="mwAp0">;</span> <span class="k" id="mwAp4">consteval</span><span class="w" id="mwAp8"> </span><span class="kt" id="mwAqA">bool</span><span class="w" id="mwAqE"> </span><span class="nf" id="mwAqI">isNonstaticMethod</span><span class="p" id="mwAqM">(</span><span class="n" id="mwAqQ">info</span><span class="w" id="mwAqU"> </span><span class="n" id="mwAqY">mem</span><span class="p" id="mwAqc">)</span><span class="w" id="mwAqg"> </span><span class="k" id="mwAqk">noexcept</span><span class="w" id="mwAqo"> </span><span class="p" id="mwAqs">{</span> <span class="w" id="mwAqw"> </span><span class="k" id="mwAq0">return</span><span class="w" id="mwAq4"> </span><span class="n" id="mwAq8">meta</span><span class="o" id="mwArA">::</span><span class="n" id="mwArE">is_class_member</span><span class="p" id="mwArI">(</span><span class="n" id="mwArM">mem</span><span class="p" id="mwArQ">)</span><span class="w" id="mwArU"> </span><span class="o" id="mwArY">&&</span> <span class="w" id="mwArc"> </span><span class="o" id="mwArg">!</span><span class="n" id="mwArk">meta</span><span class="o" id="mwAro">::</span><span class="n" id="mwArs">is_static_member</span><span class="p" id="mwArw">(</span><span class="n" id="mwAr0">mem</span><span class="p" id="mwAr4">)</span><span class="w" id="mwAr8"> </span><span class="o" id="mwAsA">&&</span> <span class="w" id="mwAsE"> </span><span class="n" id="mwAsI">meta</span><span class="o" id="mwAsM">::</span><span class="n" id="mwAsQ">is_function</span><span class="p" id="mwAsU">(</span><span class="n" id="mwAsY">mem</span><span class="p" id="mwAsc">);</span> <span class="p" id="mwAsg">}</span> <span class="k" id="mwAsk">consteval</span><span class="w" id="mwAso"> </span><span class="n" id="mwAss">info</span><span class="w" id="mwAsw"> </span><span class="nf" id="mwAs0">findMethod</span><span class="p" id="mwAs4">(</span><span class="n" id="mwAs8">info</span><span class="w" id="mwAtA"> </span><span class="n" id="mwAtE">type</span><span class="p" id="mwAtI">,</span><span class="w" id="mwAtM"> </span><span class="n" id="mwAtQ">string_view</span><span class="w" id="mwAtU"> </span><span class="n" id="mwAtY">name</span><span class="p" id="mwAtc">)</span><span class="w" id="mwAtg"> </span><span class="p" id="mwAtk">{</span> <span class="w" id="mwAto"> </span><span class="k" id="mwAts">for</span><span class="w" id="mwAtw"> </span><span class="p" id="mwAt0">(</span><span class="n" id="mwAt4">info</span><span class="w" id="mwAt8"> </span><span class="n" id="mwAuA">member</span><span class="w" id="mwAuE"> </span><span class="o" id="mwAuI">:</span><span class="w" id="mwAuM"> </span><span class="n" id="mwAuQ">meta</span><span class="o" id="mwAuU">::</span><span class="n" id="mwAuY">members_of</span><span class="p" id="mwAuc">(</span><span class="n" id="mwAug">type</span><span class="p" id="mwAuk">,</span><span class="w" id="mwAuo"> </span><span class="n" id="mwAus">access_context</span><span class="o" id="mwAuw">::</span><span class="n" id="mwAu0">current</span><span class="p" id="mwAu4">())</span> <span class="w" id="mwAu8"> </span><span class="o" id="mwAvA">|</span><span class="w" id="mwAvE"> </span><span class="n" id="mwAvI">filter</span><span class="p" id="mwAvM">(</span><span class="n" id="mwAvQ">isNonstaticMethod</span><span class="p" id="mwAvU">))</span><span class="w" id="mwAvY"> </span><span class="p" id="mwAvc">{</span> <span class="w" id="mwAvg"> </span><span class="k" id="mwAvk">if</span><span class="w" id="mwAvo"> </span><span class="p" id="mwAvs">(</span><span class="n" id="mwAvw">meta</span><span class="o" id="mwAv0">::</span><span class="n" id="mwAv4">has_identifier</span><span class="p" id="mwAv8">(</span><span class="n" id="mwAwA">member</span><span class="p" id="mwAwE">)</span><span class="w" id="mwAwI"> </span><span class="o" id="mwAwM">&&</span><span class="w" id="mwAwQ"> </span><span class="n" id="mwAwU">meta</span><span class="o" id="mwAwY">::</span><span class="n" id="mwAwc">identifier_of</span><span class="p" id="mwAwg">(</span><span class="n" id="mwAwk">member</span><span class="p" id="mwAwo">)</span><span class="w" id="mwAws"> </span><span class="o" id="mwAww">==</span><span class="w" id="mwAw0"> </span><span class="n" id="mwAw4">name</span><span class="p" id="mwAw8">)</span><span class="w" id="mwAxA"> </span><span class="p" id="mwAxE">{</span> <span class="w" id="mwAxI"> </span><span class="k" id="mwAxM">return</span><span class="w" id="mwAxQ"> </span><span class="n" id="mwAxU">member</span><span class="p" id="mwAxY">;</span> <span class="w" id="mwAxc"> </span><span class="p" id="mwAxg">}</span> <span class="w" id="mwAxk"> </span><span class="p" id="mwAxo">}</span> <span class="w" id="mwAxs"> </span><span class="c1" id="mwAxw">// Note: this is std::meta::exception, not std::exception</span> <span class="w" id="mwAx0"> </span><span class="k" id="mwAx4">throw</span><span class="w" id="mwAx8"> </span><span class="n" id="mwAyA">exception</span><span class="p" id="mwAyE">(</span><span class="n" id="mwAyI">std</span><span class="o" id="mwAyM">::</span><span class="n" id="mwAyQ">format</span><span class="p" id="mwAyU">(</span><span class="s" id="mwAyY">"Failed to retrieve method {} from type {}"</span><span class="p" id="mwAyc">,</span><span class="w" id="mwAyg"> </span><span class="n" id="mwAyk">name</span><span class="p" id="mwAyo">,</span><span class="w" id="mwAys"> </span><span class="n" id="mwAyw">meta</span><span class="o" id="mwAy0">::</span><span class="n" id="mwAy4">identifier_of</span><span class="p" id="mwAy8">(</span><span class="n" id="mwAzA">type</span><span class="p" id="mwAzE">)),</span><span class="w" id="mwAzI"> </span><span class="o" id="mwAzM">^^</span><span class="n" id="mwAzQ">findMethod</span><span class="p" id="mwAzU">);</span> <span class="p" id="mwAzY">}</span> <span class="k" id="mwAzc">template</span><span class="w" id="mwAzg"> </span><span class="o" id="mwAzk"><</span><span class="n" id="mwAzo">info</span><span class="w" id="mwAzs"> </span><span class="n" id="mwAzw">T</span><span class="p" id="mwAz0">,</span><span class="w" id="mwAz4"> </span><span class="k" id="mwAz8">const</span><span class="w" id="mwA0A"> </span><span class="kt" id="mwA0E">char</span><span class="o" id="mwA0I">*</span><span class="w" id="mwA0M"> </span><span class="n" id="mwA0Q">Name</span><span class="o" id="mwA0U">></span> <span class="k" id="mwA0Y">constexpr</span><span class="w" id="mwA0c"> </span><span class="k" id="mwA0g">auto</span><span class="w" id="mwA0k"> </span><span class="n" id="mwA0o">createInvokerImpl</span><span class="w" id="mwA0s"> </span><span class="o" id="mwA0w">=</span><span class="w" id="mwA00"> </span><span class="p" id="mwA04">[]</span><span class="w" id="mwA08"> </span><span class="o" id="mwA1A">-></span><span class="w" id="mwA1E"> </span><span class="k" id="mwA1I">auto</span><span class="w" id="mwA1M"> </span><span class="p" id="mwA1Q">{</span> <span class="w" id="mwA1U"> </span><span class="k" id="mwA1Y">static</span><span class="w" id="mwA1c"> </span><span class="k" id="mwA1g">constexpr</span><span class="w" id="mwA1k"> </span><span class="n" id="mwA1o">info</span><span class="w" id="mwA1s"> </span><span class="n" id="mwA1w">M</span><span class="w" id="mwA10"> </span><span class="o" id="mwA14">=</span><span class="w" id="mwA18"> </span><span class="n" id="mwA2A">findMethod</span><span class="p" id="mwA2E">(</span><span class="n" id="mwA2I">T</span><span class="p" id="mwA2M">,</span><span class="w" id="mwA2Q"> </span><span class="n" id="mwA2U">Name</span><span class="p" id="mwA2Y">);</span> <span class="w" id="mwA2c"> </span><span class="k" id="mwA2g">static_assert</span><span class="p" id="mwA2k">(</span> <span class="w" id="mwA2o"> </span><span class="n" id="mwA2s">meta</span><span class="o" id="mwA2w">::</span><span class="n" id="mwA20">parameters_of</span><span class="p" id="mwA24">(</span><span class="n" id="mwA28">M</span><span class="p" id="mwA3A">).</span><span class="n" id="mwA3E">size</span><span class="p" id="mwA3I">()</span><span class="w" id="mwA3M"> </span><span class="o" id="mwA3Q">==</span><span class="w" id="mwA3U"> </span><span class="mi" id="mwA3Y">0</span><span class="w" id="mwA3c"> </span><span class="o" id="mwA3g">&&</span><span class="w" id="mwA3k"> </span><span class="n" id="mwA3o">meta</span><span class="o" id="mwA3s">::</span><span class="n" id="mwA3w">return_type_of</span><span class="p" id="mwA30">(</span><span class="n" id="mwA34">M</span><span class="p" id="mwA38">)</span><span class="w" id="mwA4A"> </span><span class="o" id="mwA4E">==</span><span class="w" id="mwA4I"> </span><span class="o" id="mwA4M">^^</span><span class="kt" id="mwA4Q">void</span><span class="p" id="mwA4U">,</span> <span class="w" id="mwA4Y"> </span><span class="s" id="mwA4c">"Reflected method must take zero parameters and return void."</span> <span class="w" id="mwA4g"> </span><span class="p" id="mwA4k">);</span> <span class="w" id="mwA4o"> </span><span class="k" id="mwA4s">return</span><span class="w" id="mwA4w"> </span><span class="p" id="mwA40">[]([</span><span class="o" id="mwA44">:</span><span class="n" id="mwA48">T</span><span class="o" id="mwA5A">:</span><span class="p" id="mwA5E">]</span><span class="o" id="mwA5I">&</span><span class="w" id="mwA5M"> </span><span class="n" id="mwA5Q">instance</span><span class="p" id="mwA5U">)</span><span class="w" id="mwA5Y"> </span><span class="o" id="mwA5c">-></span><span class="w" id="mwA5g"> </span><span class="kt" id="mwA5k">void</span><span class="w" id="mwA5o"> </span><span class="p" id="mwA5s">{</span><span class="w" id="mwA5w"> </span><span class="n" id="mwA50">instance</span><span class="p" id="mwA54">.[</span><span class="o" id="mwA58">:</span><span class="n" id="mwA6A">M</span><span class="o" id="mwA6E">:</span><span class="p" id="mwA6I">]();</span><span class="w" id="mwA6M"> </span><span class="p" id="mwA6Q">};</span> <span class="p" id="mwA6U">}();</span> <span class="k" id="mwA6Y">consteval</span><span class="w" id="mwA6c"> </span><span class="n" id="mwA6g">info</span><span class="w" id="mwA6k"> </span><span class="nf" id="mwA6o">createInvoker</span><span class="p" id="mwA6s">(</span><span class="n" id="mwA6w">info</span><span class="w" id="mwA60"> </span><span class="n" id="mwA64">type</span><span class="p" id="mwA68">,</span><span class="w" id="mwA7A"> </span><span class="n" id="mwA7E">string_view</span><span class="w" id="mwA7I"> </span><span class="n" id="mwA7M">name</span><span class="p" id="mwA7Q">)</span><span class="w" id="mwA7U"> </span><span class="p" id="mwA7Y">{</span> <span class="w" id="mwA7c"> </span><span class="k" id="mwA7g">return</span><span class="w" id="mwA7k"> </span><span class="n" id="mwA7o">meta</span><span class="o" id="mwA7s">::</span><span class="n" id="mwA7w">substitute</span><span class="p" id="mwA70">(</span> <span class="w" id="mwA74"> </span><span class="o" id="mwA78">^^</span><span class="n" id="mwA8A">createInvokerImpl</span><span class="p" id="mwA8E">,</span> <span class="w" id="mwA8I"> </span><span class="p" id="mwA8M">{</span><span class="w" id="mwA8Q"> </span><span class="n" id="mwA8U">meta</span><span class="o" id="mwA8Y">::</span><span class="n" id="mwA8c">reflect_constant</span><span class="p" id="mwA8g">(</span><span class="n" id="mwA8k">type</span><span class="p" id="mwA8o">),</span><span class="w" id="mwA8s"> </span><span class="n" id="mwA8w">meta</span><span class="o" id="mwA80">::</span><span class="n" id="mwA84">reflect_constant_string</span><span class="p" id="mwA88">(</span><span class="n" id="mwA9A">name</span><span class="p" id="mwA9E">)</span><span class="w" id="mwA9I"> </span><span class="p" id="mwA9M">}</span> <span class="w" id="mwA9Q"> </span><span class="p" id="mwA9U">);</span> <span class="p" id="mwA9Y">}</span> <span class="k" id="mwA9c">class</span><span class="w" id="mwA9g"> </span><span class="nc" id="mwA9k">Foo</span><span class="w" id="mwA9o"> </span><span class="p" id="mwA9s">{</span> <span class="k" id="mwA9w">private</span><span class="o" id="mwA90">:</span> <span class="w" id="mwA94"> </span><span class="c1" id="mwA98">// ...</span> <span class="k" id="mwA-A">public</span><span class="o" id="mwA-E">:</span> <span class="w" id="mwA-I"> </span><span class="n" id="mwA-M">Foo</span><span class="p" id="mwA-Q">()</span><span class="w" id="mwA-U"> </span><span class="o" id="mwA-Y">=</span><span class="w" id="mwA-c"> </span><span class="k" id="mwA-g">default</span><span class="p" id="mwA-k">;</span> <span class="w" id="mwA-o"> </span><span class="kt" id="mwA-s">void</span><span class="w" id="mwA-w"> </span><span class="nf" id="mwA-0">printHello</span><span class="p" id="mwA-4">()</span><span class="w" id="mwA-8"> </span><span class="k" id="mwA_A">const</span><span class="w" id="mwA_E"> </span><span class="p" id="mwA_I">{</span> <span class="w" id="mwA_M"> </span><span class="n" id="mwA_Q">std</span><span class="o" id="mwA_U">::</span><span class="n" id="mwA_Y">println</span><span class="p" id="mwA_c">(</span><span class="s" id="mwA_g">"Hello, world!"</span><span class="p" id="mwA_k">);</span> <span class="w" id="mwA_o"> </span><span class="p" id="mwA_s">}</span> <span class="p" id="mwA_w">};</span> <span class="kt" id="mwA_0">int</span><span class="w" id="mwA_4"> </span><span class="nf" id="mwA_8">main</span><span class="p" id="mwBAA">(</span><span class="kt" id="mwBAE">int</span><span class="w" id="mwBAI"> </span><span class="n" id="mwBAM">argc</span><span class="p" id="mwBAQ">,</span><span class="w" id="mwBAU"> </span><span class="kt" id="mwBAY">char</span><span class="o" id="mwBAc">*</span><span class="w" id="mwBAg"> </span><span class="n" id="mwBAk">argv</span><span class="p" id="mwBAo">[])</span><span class="w" id="mwBAs"> </span><span class="p" id="mwBAw">{</span> <span class="w" id="mwBA0"> </span><span class="n" id="mwBA4">Foo</span><span class="w" id="mwBA8"> </span><span class="n" id="mwBBA">foo</span><span class="p" id="mwBBE">;</span> <span class="w" id="mwBBI"> </span><span class="c1" id="mwBBM">// Without reflection</span> <span class="w" id="mwBBQ"> </span><span class="n" id="mwBBU">foo</span><span class="p" id="mwBBY">.</span><span class="n" id="mwBBc">printHello</span><span class="p" id="mwBBg">();</span> <span class="w" id="mwBBk"> </span><span class="c1" id="mwBBo">// With reflection</span> <span class="w" id="mwBBs"> </span><span class="k" id="mwBBw">auto</span><span class="w" id="mwBB0"> </span><span class="n" id="mwBB4">invokePrint</span><span class="w" id="mwBB8"> </span><span class="o" id="mwBCA">=</span><span class="w" id="mwBCE"> </span><span class="p" id="mwBCI">[</span><span class="o" id="mwBCM">:</span><span class="n" id="mwBCQ">createInvoker</span><span class="p" id="mwBCU">(</span><span class="o" id="mwBCY">^^</span><span class="n" id="mwBCc">Foo</span><span class="p" id="mwBCg">,</span><span class="w" id="mwBCk"> </span><span class="s" id="mwBCo">"printHello"</span><span class="p" id="mwBCs">)</span><span class="o" id="mwBCw">:</span><span class="p" id="mwBC0">];</span> <span class="w" id="mwBC4"> </span><span class="n" id="mwBC8">invokePrint</span><span class="p" id="mwBDA">(</span><span class="n" id="mwBDE">foo</span><span class="p" id="mwBDI">);</span> <span class="w" id="mwBDM"> </span><span class="k" id="mwBDQ">return</span><span class="w" id="mwBDU"> </span><span class="mi" id="mwBDY">0</span><span class="p" id="mwBDc">;</span> <span class="p" id="mwBDg">}</span>

C#

The example below is in C#:

<span id="mwBD4"></span><span class="k" id="mwBD8">namespace</span><span class="w" id="mwBEA"> </span><span class="nn" id="mwBEE">Wikipedia.Examples</span><span class="p" id="mwBEI">;</span> <span class="k" id="mwBEM">using</span><span class="w" id="mwBEQ"> </span><span class="nn" id="mwBEU">System</span><span class="p" id="mwBEY">;</span> <span class="k" id="mwBEc">using</span><span class="w" id="mwBEg"> </span><span class="nn" id="mwBEk">System.Reflection</span><span class="p" id="mwBEo">;</span> <span class="k" id="mwBEs">class</span><span class="w" id="mwBEw"> </span><span class="nc" id="mwBE0">Foo</span> <span class="p" id="mwBE4">{</span> <span class="w" id="mwBE8"> </span><span class="c1" id="mwBFA">// ...</span> <span class="w" id="mwBFE"> </span><span class="k" id="mwBFI">public</span><span class="w" id="mwBFM"> </span><span class="k" id="mwBFQ">void</span><span class="w" id="mwBFU"> </span><span class="nf" id="mwBFY">PrintHello</span><span class="p" id="mwBFc">()</span> <span class="w" id="mwBFg"> </span><span class="p" id="mwBFk">{</span> <span class="w" id="mwBFo"> </span><span class="n" id="mwBFs">Console</span><span class="p" id="mwBFw">.</span><span class="n" id="mwBF0">WriteLine</span><span class="p" id="mwBF4">(</span><span class="s" id="mwBF8">"Hello, world!"</span><span class="p" id="mwBGA">);</span> <span class="w" id="mwBGE"> </span><span class="p" id="mwBGI">}</span> <span class="p" id="mwBGM">}</span> <span class="k" id="mwBGQ">public</span><span class="w" id="mwBGU"> </span><span class="k" id="mwBGY">class</span><span class="w" id="mwBGc"> </span><span class="nc" id="mwBGg">InvokeFooExample</span> <span class="p" id="mwBGk">{</span> <span class="w" id="mwBGo"> </span><span class="k" id="mwBGs">static</span><span class="w" id="mwBGw"> </span><span class="k" id="mwBG0">void</span><span class="w" id="mwBG4"> </span><span class="nf" id="mwBG8">Main</span><span class="p" id="mwBHA">(</span><span class="kt" id="mwBHE">string</span><span class="p" id="mwBHI">[]</span><span class="w" id="mwBHM"> </span><span class="n" id="mwBHQ">args</span><span class="p" id="mwBHU">)</span> <span class="w" id="mwBHY"> </span><span class="p" id="mwBHc">{</span> <span class="w" id="mwBHg"> </span><span class="c1" id="mwBHk">// Without reflection</span> <span class="w" id="mwBHo"> </span><span class="n" id="mwBHs">Foo</span><span class="w" id="mwBHw"> </span><span class="n" id="mwBH0">foo</span><span class="w" id="mwBH4"> </span><span class="o" id="mwBH8">=</span><span class="w" id="mwBIA"> </span><span class="k" id="mwBIE">new</span><span class="p" id="mwBII">();</span> <span class="w" id="mwBIM"> </span><span class="n" id="mwBIQ">foo</span><span class="p" id="mwBIU">.</span><span class="n" id="mwBIY">PrintHello</span><span class="p" id="mwBIc">();</span> <span class="w" id="mwBIg"> </span><span class="c1" id="mwBIk">// With reflection</span> <span class="w" id="mwBIo"> </span><span class="n" id="mwBIs">Object</span><span class="w" id="mwBIw"> </span><span class="n" id="mwBI0">reflectedFoo</span><span class="w" id="mwBI4"> </span><span class="o" id="mwBI8">=</span><span class="w" id="mwBJA"> </span><span class="n" id="mwBJE">Activator</span><span class="p" id="mwBJI">.</span><span class="n" id="mwBJM">CreateInstance</span><span class="p" id="mwBJQ">(</span><span class="k" id="mwBJU">typeof</span><span class="p" id="mwBJY">(</span><span class="n" id="mwBJc">Foo</span><span class="p" id="mwBJg">));</span> <span class="w" id="mwBJk"> </span><span class="n" id="mwBJo">MethodInfo</span><span class="w" id="mwBJs"> </span><span class="n" id="mwBJw">method</span><span class="w" id="mwBJ0"> </span><span class="o" id="mwBJ4">=</span><span class="w" id="mwBJ8"> </span><span class="n" id="mwBKA">reflectedFoo</span><span class="p" id="mwBKE">.</span><span class="n" id="mwBKI">GetType</span><span class="p" id="mwBKM">()</span> <span class="w" id="mwBKQ"> </span><span class="p" id="mwBKU">.</span><span class="n" id="mwBKY">GetMethod</span><span class="p" id="mwBKc">(</span><span class="s" id="mwBKg">"PrintHello"</span><span class="p" id="mwBKk">);</span> <span class="w" id="mwBKo"> </span><span class="n" id="mwBKs">method</span><span class="p" id="mwBKw">.</span><span class="n" id="mwBK0">Invoke</span><span class="p" id="mwBK4">(</span><span class="n" id="mwBK8">foo</span><span class="p" id="mwBLA">,</span><span class="w" id="mwBLE"> </span><span class="k" id="mwBLI">null</span><span class="p" id="mwBLM">);</span> <span class="w" id="mwBLQ"> </span><span class="p" id="mwBLU">}</span> <span class="p" id="mwBLY">}</span>

Delphi, Object Pascal

This Delphi and Object Pascal example assumes that a TFoo class has been declared in a unit called Unit1:

<span id="mwBME"></span><span class="k" id="mwBMI">uses</span><span class="w" id="mwBMM"> </span><span class="n" id="mwBMQ">RTTI</span><span class="o" id="mwBMU">,</span><span class="w" id="mwBMY"> </span><span class="n" id="mwBMc">Unit1</span><span class="o" id="mwBMg">;</span> <span class="k" id="mwBMk">procedure</span><span class="w" id="mwBMo"> </span><span class="nf" id="mwBMs">WithoutReflection</span><span class="o" id="mwBMw">;</span> <span class="k" id="mwBM0">var</span> <span class="w" id="mwBM4"> </span><span class="n" id="mwBM8">Foo</span><span class="o" id="mwBNA">:</span><span class="w" id="mwBNE"> </span><span class="n" id="mwBNI">TFoo</span><span class="o" id="mwBNM">;</span> <span class="k" id="mwBNQ">begin</span> <span class="w" id="mwBNU"> </span><span class="n" id="mwBNY">Foo</span><span class="w" id="mwBNc"> </span><span class="o" id="mwBNg">:=</span><span class="w" id="mwBNk"> </span><span class="n" id="mwBNo">TFoo</span><span class="o" id="mwBNs">.</span><span class="n" id="mwBNw">Create</span><span class="o" id="mwBN0">;</span> <span class="w" id="mwBN4"> </span><span class="k" id="mwBN8">try</span> <span class="w" id="mwBOA"> </span><span class="n" id="mwBOE">Foo</span><span class="o" id="mwBOI">.</span><span class="n" id="mwBOM">Hello</span><span class="o" id="mwBOQ">;</span> <span class="w" id="mwBOU"> </span><span class="k" id="mwBOY">finally</span> <span class="w" id="mwBOc"> </span><span class="n" id="mwBOg">Foo</span><span class="o" id="mwBOk">.</span><span class="n" id="mwBOo">Free</span><span class="o" id="mwBOs">;</span> <span class="w" id="mwBOw"> </span><span class="k" id="mwBO0">end</span><span class="o" id="mwBO4">;</span> <span class="k" id="mwBO8">end</span><span class="o" id="mwBPA">;</span> <span class="k" id="mwBPE">procedure</span><span class="w" id="mwBPI"> </span><span class="nf" id="mwBPM">WithReflection</span><span class="o" id="mwBPQ">;</span> <span class="k" id="mwBPU">var</span> <span class="w" id="mwBPY"> </span><span class="n" id="mwBPc">RttiContext</span><span class="o" id="mwBPg">:</span><span class="w" id="mwBPk"> </span><span class="n" id="mwBPo">TRttiContext</span><span class="o" id="mwBPs">;</span> <span class="w" id="mwBPw"> </span><span class="n" id="mwBP0">RttiType</span><span class="o" id="mwBP4">:</span><span class="w" id="mwBP8"> </span><span class="n" id="mwBQA">TRttiInstanceType</span><span class="o" id="mwBQE">;</span> <span class="w" id="mwBQI"> </span><span class="n" id="mwBQM">Foo</span><span class="o" id="mwBQQ">:</span><span class="w" id="mwBQU"> </span><span class="kt" id="mwBQY">TObject</span><span class="o" id="mwBQc">;</span> <span class="k" id="mwBQg">begin</span> <span class="w" id="mwBQk"> </span><span class="n" id="mwBQo">RttiType</span><span class="w" id="mwBQs"> </span><span class="o" id="mwBQw">:=</span><span class="w" id="mwBQ0"> </span><span class="n" id="mwBQ4">RttiContext</span><span class="o" id="mwBQ8">.</span><span class="n" id="mwBRA">FindType</span><span class="p" id="mwBRE">(</span><span class="s" id="mwBRI">'Unit1.TFoo'</span><span class="p" id="mwBRM">)</span><span class="w" id="mwBRQ"> </span><span class="k" id="mwBRU">as</span><span class="w" id="mwBRY"> </span><span class="n" id="mwBRc">TRttiInstanceType</span><span class="o" id="mwBRg">;</span> <span class="w" id="mwBRk"> </span><span class="n" id="mwBRo">Foo</span><span class="w" id="mwBRs"> </span><span class="o" id="mwBRw">:=</span><span class="w" id="mwBR0"> </span><span class="n" id="mwBR4">RttiType</span><span class="o" id="mwBR8">.</span><span class="n" id="mwBSA">GetMethod</span><span class="p" id="mwBSE">(</span><span class="s" id="mwBSI">'Create'</span><span class="p" id="mwBSM">)</span><span class="o" id="mwBSQ">.</span><span class="n" id="mwBSU">Invoke</span><span class="p" id="mwBSY">(</span><span class="n" id="mwBSc">RttiType</span><span class="o" id="mwBSg">.</span><span class="n" id="mwBSk">MetaclassType</span><span class="o" id="mwBSo">,</span><span class="w" id="mwBSs"> </span><span class="p" id="mwBSw">[])</span><span class="o" id="mwBS0">.</span><span class="n" id="mwBS4">AsObject</span><span class="o" id="mwBS8">;</span> <span class="w" id="mwBTA"> </span><span class="k" id="mwBTE">try</span> <span class="w" id="mwBTI"> </span><span class="n" id="mwBTM">RttiType</span><span class="o" id="mwBTQ">.</span><span class="n" id="mwBTU">GetMethod</span><span class="p" id="mwBTY">(</span><span class="s" id="mwBTc">'Hello'</span><span class="p" id="mwBTg">)</span><span class="o" id="mwBTk">.</span><span class="n" id="mwBTo">Invoke</span><span class="p" id="mwBTs">(</span><span class="n" id="mwBTw">Foo</span><span class="o" id="mwBT0">,</span><span class="w" id="mwBT4"> </span><span class="p" id="mwBT8">[])</span><span class="o" id="mwBUA">;</span> <span class="w" id="mwBUE"> </span><span class="k" id="mwBUI">finally</span> <span class="w" id="mwBUM"> </span><span class="n" id="mwBUQ">Foo</span><span class="o" id="mwBUU">.</span><span class="n" id="mwBUY">Free</span><span class="o" id="mwBUc">;</span> <span class="w" id="mwBUg"> </span><span class="k" id="mwBUk">end</span><span class="o" id="mwBUo">;</span> <span class="k" id="mwBUs">end</span><span class="o" id="mwBUw">;</span>

eC

The example below is in eC:

<span id="mwBVE"></span><span class="c1" id="mwBVI">// Without reflection</span> <span class="n" id="mwBVM">Foo</span><span class="w" id="mwBVQ"> </span><span class="n" id="mwBVU">foo</span><span class="p" id="mwBVY">{};</span> <span class="n" id="mwBVc">foo</span><span class="p" id="mwBVg">.</span><span class="n" id="mwBVk">hello</span><span class="p" id="mwBVo">();</span> <span class="c1" id="mwBVs">// With reflection</span> <span class="n" id="mwBVw">Class</span><span class="w" id="mwBV0"> </span><span class="n" id="mwBV4">fooClass</span><span class="w" id="mwBV8"> </span><span class="o" id="mwBWA">=</span><span class="w" id="mwBWE"> </span><span class="n" id="mwBWI">eSystem_FindClass</span><span class="p" id="mwBWM">(</span><span class="n" id="mwBWQ">__thisModule</span><span class="p" id="mwBWU">,</span><span class="w" id="mwBWY"> </span><span class="s" id="mwBWc">"Foo"</span><span class="p" id="mwBWg">);</span> <span class="n" id="mwBWk">Instance</span><span class="w" id="mwBWo"> </span><span class="n" id="mwBWs">foo</span><span class="w" id="mwBWw"> </span><span class="o" id="mwBW0">=</span><span class="w" id="mwBW4"> </span><span class="n" id="mwBW8">eInstance_New</span><span class="p" id="mwBXA">(</span><span class="n" id="mwBXE">fooClass</span><span class="p" id="mwBXI">);</span> <span class="n" id="mwBXM">Method</span><span class="w" id="mwBXQ"> </span><span class="n" id="mwBXU">m</span><span class="w" id="mwBXY"> </span><span class="o" id="mwBXc">=</span><span class="w" id="mwBXg"> </span><span class="n" id="mwBXk">eClass_FindMethod</span><span class="p" id="mwBXo">(</span><span class="n" id="mwBXs">fooClass</span><span class="p" id="mwBXw">,</span><span class="w" id="mwBX0"> </span><span class="s" id="mwBX4">"hello"</span><span class="p" id="mwBX8">,</span><span class="w" id="mwBYA"> </span><span class="n" id="mwBYE">fooClass</span><span class="p" id="mwBYI">.</span><span class="n" id="mwBYM">module</span><span class="p" id="mwBYQ">);</span> <span class="p" id="mwBYU">((</span><span class="kt" id="mwBYY">void</span><span class="p" id="mwBYc">(</span><span class="o" id="mwBYg">*</span><span class="p" id="mwBYk">)())(</span><span class="kt" id="mwBYo">void</span><span class="o" id="mwBYs">*</span><span class="p" id="mwBYw">)</span><span class="n" id="mwBY0">m</span><span class="p" id="mwBY4">.</span><span class="n" id="mwBY8">function</span><span class="p" id="mwBZA">)(</span><span class="n" id="mwBZE">foo</span><span class="p" id="mwBZI">);</span>

Go

The example below is in Go:

<span id="mwBZg"></span><span class="kn" id="mwBZk">import</span><span class="w" id="mwBZo"> </span><span class="p" id="mwBZs">(</span> <span class="w" id="mwBZw"> </span><span class="s" id="mwBZ0">"fmt"</span> <span class="w" id="mwBZ4"> </span><span class="s" id="mwBZ8">"reflect"</span> <span class="p" id="mwBaA">)</span> <span class="kd" id="mwBaE">type</span><span class="w" id="mwBaI"> </span><span class="nx" id="mwBaM">Foo</span><span class="w" id="mwBaQ"> </span><span class="kd" id="mwBaU">struct</span><span class="p" id="mwBaY">{}</span> <span class="kd" id="mwBac">func</span><span class="w" id="mwBag"> </span><span class="p" id="mwBak">(</span><span class="nx" id="mwBao">f</span><span class="w" id="mwBas"> </span><span class="nx" id="mwBaw">Foo</span><span class="p" id="mwBa0">)</span><span class="w" id="mwBa4"> </span><span class="nx" id="mwBa8">Hello</span><span class="p" id="mwBbA">()</span><span class="w" id="mwBbE"> </span><span class="p" id="mwBbI">{</span> <span class="w" id="mwBbM"> </span><span class="nx" id="mwBbQ">fmt</span><span class="p" id="mwBbU">.</span><span class="nx" id="mwBbY">Println</span><span class="p" id="mwBbc">(</span><span class="s" id="mwBbg">"Hello, world!"</span><span class="p" id="mwBbk">)</span> <span class="p" id="mwBbo">}</span> <span class="kd" id="mwBbs">func</span><span class="w" id="mwBbw"> </span><span class="nx" id="mwBb0">main</span><span class="p" id="mwBb4">()</span><span class="w" id="mwBb8"> </span><span class="p" id="mwBcA">{</span> <span class="w" id="mwBcE"> </span><span class="c1" id="mwBcI">// Without reflection</span> <span class="w" id="mwBcM"> </span><span class="kd" id="mwBcQ">var</span><span class="w" id="mwBcU"> </span><span class="nx" id="mwBcY">f</span><span class="w" id="mwBcc"> </span><span class="nx" id="mwBcg">Foo</span> <span class="w" id="mwBck"> </span><span class="nx" id="mwBco">f</span><span class="p" id="mwBcs">.</span><span class="nx" id="mwBcw">Hello</span><span class="p" id="mwBc0">()</span> <span class="w" id="mwBc4"> </span><span class="c1" id="mwBc8">// With reflection</span> <span class="w" id="mwBdA"> </span><span class="kd" id="mwBdE">var</span><span class="w" id="mwBdI"> </span><span class="nx" id="mwBdM">fT</span><span class="w" id="mwBdQ"> </span><span class="nx" id="mwBdU">reflect</span><span class="p" id="mwBdY">.</span><span class="nx" id="mwBdc">Type</span><span class="w" id="mwBdg"> </span><span class="o" id="mwBdk">=</span><span class="w" id="mwBdo"> </span><span class="nx" id="mwBds">reflect</span><span class="p" id="mwBdw">.</span><span class="nx" id="mwBd0">TypeOf</span><span class="p" id="mwBd4">(</span><span class="nx" id="mwBd8">Foo</span><span class="p" id="mwBeA">{})</span> <span class="w" id="mwBeE"> </span><span class="kd" id="mwBeI">var</span><span class="w" id="mwBeM"> </span><span class="nx" id="mwBeQ">fV</span><span class="w" id="mwBeU"> </span><span class="nx" id="mwBeY">reflect</span><span class="p" id="mwBec">.</span><span class="nx" id="mwBeg">Value</span><span class="w" id="mwBek"> </span><span class="o" id="mwBeo">=</span><span class="w" id="mwBes"> </span><span class="nx" id="mwBew">reflect</span><span class="p" id="mwBe0">.</span><span class="nx" id="mwBe4">New</span><span class="p" id="mwBe8">(</span><span class="nx" id="mwBfA">fT</span><span class="p" id="mwBfE">)</span> <span class="w" id="mwBfI"> </span><span class="kd" id="mwBfM">var</span><span class="w" id="mwBfQ"> </span><span class="nx" id="mwBfU">m</span><span class="w" id="mwBfY"> </span><span class="nx" id="mwBfc">reflect</span><span class="p" id="mwBfg">.</span><span class="nx" id="mwBfk">Value</span><span class="w" id="mwBfo"> </span><span class="o" id="mwBfs">=</span><span class="w" id="mwBfw"> </span><span class="nx" id="mwBf0">fV</span><span class="p" id="mwBf4">.</span><span class="nx" id="mwBf8">MethodByName</span><span class="p" id="mwBgA">(</span><span class="s" id="mwBgE">"Hello"</span><span class="p" id="mwBgI">)</span> <span class="w" id="mwBgM"> </span><span class="k" id="mwBgQ">if</span><span class="w" id="mwBgU"> </span><span class="nx" id="mwBgY">m</span><span class="p" id="mwBgc">.</span><span class="nx" id="mwBgg">IsValid</span><span class="p" id="mwBgk">()</span><span class="w" id="mwBgo"> </span><span class="p" id="mwBgs">{</span> <span class="w" id="mwBgw"> </span><span class="nx" id="mwBg0">m</span><span class="p" id="mwBg4">.</span><span class="nx" id="mwBg8">Call</span><span class="p" id="mwBhA">(</span><span class="kc" id="mwBhE">nil</span><span class="p" id="mwBhI">)</span> <span class="w" id="mwBhM"> </span><span class="p" id="mwBhQ">}</span><span class="w" id="mwBhU"> </span><span class="k" id="mwBhY">else</span><span class="w" id="mwBhc"> </span><span class="p" id="mwBhg">{</span> <span class="w" id="mwBhk"> </span><span class="nx" id="mwBho">fmt</span><span class="p" id="mwBhs">.</span><span class="nx" id="mwBhw">Println</span><span class="p" id="mwBh0">(</span><span class="s" id="mwBh4">"Method not found"</span><span class="p" id="mwBh8">)</span> <span class="w" id="mwBiA"> </span><span class="p" id="mwBiE">}</span> <span class="p" id="mwBiI">}</span>

Java

The example below is in Java:

<span id="mwBig"></span><span class="kn" id="mwBik">package</span><span class="w" id="mwBio"> </span><span class="nn" id="mwBis">org.wikipedia.examples</span><span class="p" id="mwBiw">;</span> <span class="kn" id="mwBi0">import</span><span class="w" id="mwBi4"> </span><span class="nn" id="mwBi8">java.lang.reflect.Method</span><span class="p" id="mwBjA">;</span> <span class="kd" id="mwBjE">class</span> <span class="nc" id="mwBjI">Foo</span><span class="w" id="mwBjM"> </span><span class="p" id="mwBjQ">{</span> <span class="w" id="mwBjU"> </span><span class="c1" id="mwBjY">// ...</span> <span class="w" id="mwBjc"> </span><span class="kd" id="mwBjg">public</span><span class="w" id="mwBjk"> </span><span class="kt" id="mwBjo">void</span><span class="w" id="mwBjs"> </span><span class="nf" id="mwBjw">printHello</span><span class="p" id="mwBj0">()</span><span class="w" id="mwBj4"> </span><span class="p" id="mwBj8">{</span> <span class="w" id="mwBkA"> </span><span class="n" id="mwBkE">System</span><span class="p" id="mwBkI">.</span><span class="na" id="mwBkM">out</span><span class="p" id="mwBkQ">.</span><span class="na" id="mwBkU">println</span><span class="p" id="mwBkY">(</span><span class="s" id="mwBkc">"Hello, world!"</span><span class="p" id="mwBkg">);</span> <span class="w" id="mwBkk"> </span><span class="p" id="mwBko">}</span> <span class="p" id="mwBks">}</span> <span class="kd" id="mwBkw">public</span><span class="w" id="mwBk0"> </span><span class="kd" id="mwBk4">class</span> <span class="nc" id="mwBk8">InvokeFooExample</span><span class="w" id="mwBlA"> </span><span class="p" id="mwBlE">{</span> <span class="w" id="mwBlI"> </span><span class="kd" id="mwBlM">public</span><span class="w" id="mwBlQ"> </span><span class="kd" id="mwBlU">static</span><span class="w" id="mwBlY"> </span><span class="kt" id="mwBlc">void</span><span class="w" id="mwBlg"> </span><span class="nf" id="mwBlk">main</span><span class="p" id="mwBlo">(</span><span class="n" id="mwBls">String</span><span class="o" id="mwBlw">[]</span><span class="w" id="mwBl0"> </span><span class="n" id="mwBl4">args</span><span class="p" id="mwBl8">)</span><span class="w" id="mwBmA"> </span><span class="p" id="mwBmE">{</span> <span class="w" id="mwBmI"> </span><span class="c1" id="mwBmM">// Without reflection</span> <span class="w" id="mwBmQ"> </span><span class="n" id="mwBmU">Foo</span><span class="w" id="mwBmY"> </span><span class="n" id="mwBmc">foo</span><span class="w" id="mwBmg"> </span><span class="o" id="mwBmk">=</span><span class="w" id="mwBmo"> </span><span class="k" id="mwBms">new</span><span class="w" id="mwBmw"> </span><span class="n" id="mwBm0">Foo</span><span class="p" id="mwBm4">();</span> <span class="w" id="mwBm8"> </span><span class="n" id="mwBnA">foo</span><span class="p" id="mwBnE">.</span><span class="na" id="mwBnI">printHello</span><span class="p" id="mwBnM">();</span> <span class="w" id="mwBnQ"> </span><span class="c1" id="mwBnU">// With reflection</span> <span class="w" id="mwBnY"> </span><span class="k" id="mwBnc">try</span><span class="w" id="mwBng"> </span><span class="p" id="mwBnk">{</span> <span class="w" id="mwBno"> </span><span class="n" id="mwBns">Foo</span><span class="w" id="mwBnw"> </span><span class="n" id="mwBn0">reflectedFoo</span><span class="w" id="mwBn4"> </span><span class="o" id="mwBn8">=</span><span class="w" id="mwBoA"> </span><span class="n" id="mwBoE">Foo</span><span class="p" id="mwBoI">.</span><span class="na" id="mwBoM">class</span> <span class="w" id="mwBoQ"> </span><span class="p" id="mwBoU">.</span><span class="na" id="mwBoY">getDeclaredConstructor</span><span class="p" id="mwBoc">()</span> <span class="w" id="mwBog"> </span><span class="p" id="mwBok">.</span><span class="na" id="mwBoo">newInstance</span><span class="p" id="mwBos">();</span> <span class="w" id="mwBow"> </span><span class="n" id="mwBo0">Method</span><span class="w" id="mwBo4"> </span><span class="n" id="mwBo8">m</span><span class="w" id="mwBpA"> </span><span class="o" id="mwBpE">=</span><span class="w" id="mwBpI"> </span><span class="n" id="mwBpM">reflectedFoo</span><span class="p" id="mwBpQ">.</span><span class="na" id="mwBpU">getClass</span><span class="p" id="mwBpY">()</span> <span class="w" id="mwBpc"> </span><span class="p" id="mwBpg">.</span><span class="na" id="mwBpk">getDeclaredMethod</span><span class="p" id="mwBpo">(</span><span class="s" id="mwBps">"printHello"</span><span class="p" id="mwBpw">,</span><span class="w" id="mwBp0"> </span><span class="k" id="mwBp4">new</span><span class="w" id="mwBp8"> </span><span class="n" id="mwBqA">Class</span><span class="o" id="mwBqE"><?>[</span><span class="mi" id="mwBqI">0</span><span class="o" id="mwBqM">]</span><span class="p" id="mwBqQ">);</span> <span class="w" id="mwBqU"> </span><span class="n" id="mwBqY">m</span><span class="p" id="mwBqc">.</span><span class="na" id="mwBqg">invoke</span><span class="p" id="mwBqk">(</span><span class="n" id="mwBqo">reflectedFoo</span><span class="p" id="mwBqs">);</span> <span class="w" id="mwBqw"> </span><span class="p" id="mwBq0">}</span><span class="w" id="mwBq4"> </span><span class="k" id="mwBq8">catch</span><span class="w" id="mwBrA"> </span><span class="p" id="mwBrE">(</span><span class="n" id="mwBrI">ReflectiveOperationException</span><span class="w" id="mwBrM"> </span><span class="n" id="mwBrQ">e</span><span class="p" id="mwBrU">)</span><span class="w" id="mwBrY"> </span><span class="p" id="mwBrc">{</span> <span class="w" id="mwBrg"> </span><span class="n" id="mwBrk">System</span><span class="p" id="mwBro">.</span><span class="na" id="mwBrs">err</span><span class="p" id="mwBrw">.</span><span class="na" id="mwBr0">printf</span><span class="p" id="mwBr4">(</span><span class="s" id="mwBr8">"An error occurred: %s%n"</span><span class="p" id="mwBsA">,</span><span class="w" id="mwBsE"> </span><span class="n" id="mwBsI">e</span><span class="p" id="mwBsM">.</span><span class="na" id="mwBsQ">getMessage</span><span class="p" id="mwBsU">());</span> <span class="w" id="mwBsY"> </span><span class="p" id="mwBsc">}</span> <span class="w" id="mwBsg"> </span><span class="p" id="mwBsk">}</span> <span class="p" id="mwBso">}</span>

Java also provides an internal class (not officially in the Java Class Library) in module jdk.unsupported, sun.reflect.Reflection which is used by sun.misc.Unsafe. It contains one method, static Class<?> getCallerClass(int depth) for obtaining the class making a call at a specified depth. This is now superseded by using the class java.lang.StackWalker.StackFrame and its method Class<?> getDeclaringClass() .

Julia

The example below is in Julia:

<span id="mwBvA"></span><span class="gp" id="mwBvE">julia></span><span class="w" id="mwBvI"> </span><span class="k" id="mwBvM">struct</span> <span class="kt" id="mwBvQ">Point</span> <span class="w" id="mwBvU"> </span><span class="n" id="mwBvY">x</span><span class="o" id="mwBvc">::</span><span class="kt" id="mwBvg">Int</span> <span class="w" id="mwBvk"> </span><span class="n" id="mwBvo">y</span> <span class="w" id="mwBvs"> </span><span class="k" id="mwBvw">end</span> <span class="go" id="mwBv0"># Inspection with reflection</span> <span class="gp" id="mwBv4">julia></span><span class="w" id="mwBv8"> </span><span class="n" id="mwBwA">fieldnames</span><span class="p" id="mwBwE">(</span><span class="n" id="mwBwI">Point</span><span class="p" id="mwBwM">)</span> <span class="go" id="mwBwQ">(:x, :y)</span> <span class="gp" id="mwBwU">julia></span><span class="w" id="mwBwY"> </span><span class="n" id="mwBwc">fieldtypes</span><span class="p" id="mwBwg">(</span><span class="n" id="mwBwk">Point</span><span class="p" id="mwBwo">)</span> <span class="go" id="mwBws">(Int64, Any)</span> <span class="gp" id="mwBww">julia></span><span class="w" id="mwBw0"> </span><span class="n" id="mwBw4">p</span><span class="w" id="mwBw8"> </span><span class="o" id="mwBxA">=</span><span class="w" id="mwBxE"> </span><span class="n" id="mwBxI">Point</span><span class="p" id="mwBxM">(</span><span class="mi" id="mwBxQ">3</span><span class="p" id="mwBxU">,</span><span class="mi" id="mwBxY">4</span><span class="p" id="mwBxc">)</span> <span class="go" id="mwBxg"># Access with reflection</span> <span class="gp" id="mwBxk">julia></span><span class="w" id="mwBxo"> </span><span class="n" id="mwBxs">getfield</span><span class="p" id="mwBxw">(</span><span class="n" id="mwBx0">p</span><span class="p" id="mwBx4">,</span><span class="w" id="mwBx8"> </span><span class="ss" id="mwByA">:x</span><span class="p" id="mwByE">)</span> <span class="go" id="mwByI">3</span>

Kotlin

Using Java reflection:

<span id="mwByc"></span><span class="k" id="mwByg">package</span><span class="w" id="mwByk"> </span><span class="nn" id="mwByo">org.wikipedia.examples</span> <span class="k" id="mwBys">import</span><span class="w" id="mwByw"> </span><span class="nn" id="mwBy0">java.lang.reflect.Method</span> <span class="kd" id="mwBy4">class</span><span class="w" id="mwBy8"> </span><span class="nc" id="mwBzA">Foo</span><span class="w" id="mwBzE"> </span><span class="p" id="mwBzI">{</span> <span class="w" id="mwBzM"> </span><span class="c1" id="mwBzQ">// ...</span> <span class="w" id="mwBzU"> </span><span class="k" id="mwBzY">constructor</span><span class="p" id="mwBzc">()</span> <span class="w" id="mwBzg"> </span><span class="kd" id="mwBzk">fun</span><span class="w" id="mwBzo"> </span><span class="nf" id="mwBzs">printHello</span><span class="p" id="mwBzw">()</span><span class="w" id="mwBz0"> </span><span class="p" id="mwBz4">{</span> <span class="w" id="mwBz8"> </span><span class="n" id="mwB0A">println</span><span class="p" id="mwB0E">(</span><span class="s" id="mwB0I">"Hello, world!"</span><span class="p" id="mwB0M">)</span> <span class="w" id="mwB0Q"> </span><span class="p" id="mwB0U">}</span> <span class="p" id="mwB0Y">}</span> <span class="kd" id="mwB0c">fun</span><span class="w" id="mwB0g"> </span><span class="nf" id="mwB0k">main</span><span class="p" id="mwB0o">(</span><span class="n" id="mwB0s">args</span><span class="p" id="mwB0w">:</span><span class="w" id="mwB00"> </span><span class="n" id="mwB04">Array</span><span class="o" id="mwB08"><</span><span class="kt" id="mwB1A">String</span><span class="o" id="mwB1E">></span><span class="p" id="mwB1I">)</span><span class="w" id="mwB1M"> </span><span class="p" id="mwB1Q">{</span> <span class="w" id="mwB1U"> </span><span class="c1" id="mwB1Y">// Without reflection</span> <span class="w" id="mwB1c"> </span><span class="kd" id="mwB1g">val</span><span class="w" id="mwB1k"> </span><span class="nv" id="mwB1o">foo</span><span class="w" id="mwB1s"> </span><span class="o" id="mwB1w">=</span><span class="w" id="mwB10"> </span><span class="n" id="mwB14">Foo</span><span class="p" id="mwB18">()</span> <span class="w" id="mwB2A"> </span><span class="n" id="mwB2E">foo</span><span class="p" id="mwB2I">.</span><span class="na" id="mwB2M">printHello</span><span class="p" id="mwB2Q">()</span> <span class="w" id="mwB2U"> </span><span class="c1" id="mwB2Y">// With reflection</span> <span class="w" id="mwB2c"> </span><span class="k" id="mwB2g">try</span><span class="w" id="mwB2k"> </span><span class="p" id="mwB2o">{</span> <span class="w" id="mwB2s"> </span><span class="c1" id="mwB2w">// Foo::class.java retrieves a java.lang.Class<Foo></span> <span class="w" id="mwB20"> </span><span class="kd" id="mwB24">val</span><span class="w" id="mwB28"> </span><span class="nv" id="mwB3A">reflectedFoo</span><span class="w" id="mwB3E"> </span><span class="o" id="mwB3I">=</span><span class="w" id="mwB3M"> </span><span class="n" id="mwB3Q">Foo</span><span class="o" id="mwB3U">::</span><span class="n" id="mwB3Y">class</span><span class="p" id="mwB3c">.</span><span class="na" id="mwB3g">java</span> <span class="w" id="mwB3k"> </span><span class="p" id="mwB3o">.</span><span class="na" id="mwB3s">getDeclaredConstructor</span><span class="p" id="mwB3w">()</span> <span class="w" id="mwB30"> </span><span class="p" id="mwB34">.</span><span class="na" id="mwB38">newInstance</span><span class="p" id="mwB4A">()</span> <span class="w" id="mwB4E"> </span><span class="kd" id="mwB4I">val</span><span class="w" id="mwB4M"> </span><span class="nv" id="mwB4Q">m</span><span class="p" id="mwB4U">:</span><span class="w" id="mwB4Y"> </span><span class="n" id="mwB4c">Method</span><span class="w" id="mwB4g"> </span><span class="o" id="mwB4k">=</span><span class="w" id="mwB4o"> </span><span class="n" id="mwB4s">reflectedFoo</span><span class="p" id="mwB4w">.</span><span class="na" id="mwB40">javaClass</span> <span class="w" id="mwB44"> </span><span class="p" id="mwB48">.</span><span class="na" id="mwB5A">getDeclaredMethod</span><span class="p" id="mwB5E">(</span><span class="s" id="mwB5I">"printHello"</span><span class="p" id="mwB5M">)</span> <span class="w" id="mwB5Q"> </span><span class="n" id="mwB5U">m</span><span class="p" id="mwB5Y">.</span><span class="na" id="mwB5c">invoke</span><span class="p" id="mwB5g">(</span><span class="n" id="mwB5k">reflectedFoo</span><span class="p" id="mwB5o">)</span> <span class="w" id="mwB5s"> </span><span class="p" id="mwB5w">}</span><span class="w" id="mwB50"> </span><span class="k" id="mwB54">catch</span><span class="w" id="mwB58"> </span><span class="p" id="mwB6A">(</span><span class="n" id="mwB6E">e</span><span class="p" id="mwB6I">:</span><span class="w" id="mwB6M"> </span><span class="n" id="mwB6Q">ReflectiveOperationException</span><span class="p" id="mwB6U">)</span><span class="w" id="mwB6Y"> </span><span class="p" id="mwB6c">{</span> <span class="w" id="mwB6g"> </span><span class="n" id="mwB6k">System</span><span class="p" id="mwB6o">.</span><span class="na" id="mwB6s">err</span><span class="p" id="mwB6w">.</span><span class="na" id="mwB60">printf</span><span class="p" id="mwB64">(</span><span class="s" id="mwB68">"An error occurred: %s%n"</span><span class="p" id="mwB7A">,</span><span class="w" id="mwB7E"> </span><span class="n" id="mwB7I">e</span><span class="p" id="mwB7M">.</span><span class="na" id="mwB7Q">message</span><span class="p" id="mwB7U">)</span> <span class="w" id="mwB7Y"> </span><span class="p" id="mwB7c">}</span> <span class="p" id="mwB7g">}</span>

Using pure Kotlin:

<span id="mwB7w"></span><span class="k" id="mwB70">package</span><span class="w" id="mwB74"> </span><span class="nn" id="mwB78">org.wikipedia.examples</span> <span class="k" id="mwB8A">import</span><span class="w" id="mwB8E"> </span><span class="nn" id="mwB8I">kotlin.reflect.full.createInstance</span> <span class="k" id="mwB8M">import</span><span class="w" id="mwB8Q"> </span><span class="nn" id="mwB8U">kotlin.reflect.full.functions</span> <span class="kd" id="mwB8Y">class</span><span class="w" id="mwB8c"> </span><span class="nc" id="mwB8g">Foo</span><span class="w" id="mwB8k"> </span><span class="p" id="mwB8o">{</span> <span class="w" id="mwB8s"> </span><span class="c1" id="mwB8w">// ...</span> <span class="w" id="mwB80"> </span><span class="kd" id="mwB84">fun</span><span class="w" id="mwB88"> </span><span class="nf" id="mwB9A">printHello</span><span class="p" id="mwB9E">()</span><span class="w" id="mwB9I"> </span><span class="p" id="mwB9M">{</span> <span class="w" id="mwB9Q"> </span><span class="n" id="mwB9U">println</span><span class="p" id="mwB9Y">(</span><span class="s" id="mwB9c">"Hello, world!"</span><span class="p" id="mwB9g">)</span> <span class="w" id="mwB9k"> </span><span class="p" id="mwB9o">}</span> <span class="p" id="mwB9s">}</span> <span class="kd" id="mwB9w">fun</span><span class="w" id="mwB90"> </span><span class="nf" id="mwB94">main</span><span class="p" id="mwB98">(</span><span class="n" id="mwB-A">args</span><span class="p" id="mwB-E">:</span><span class="w" id="mwB-I"> </span><span class="n" id="mwB-M">Array</span><span class="o" id="mwB-Q"><</span><span class="kt" id="mwB-U">String</span><span class="o" id="mwB-Y">></span><span class="p" id="mwB-c">)</span><span class="w" id="mwB-g"> </span><span class="p" id="mwB-k">{</span> <span class="w" id="mwB-o"> </span><span class="c1" id="mwB-s">// Without reflection</span> <span class="w" id="mwB-w"> </span><span class="kd" id="mwB-0">val</span><span class="w" id="mwB-4"> </span><span class="nv" id="mwB-8">foo</span><span class="w" id="mwB_A"> </span><span class="o" id="mwB_E">=</span><span class="w" id="mwB_I"> </span><span class="n" id="mwB_M">Foo</span><span class="p" id="mwB_Q">()</span> <span class="w" id="mwB_U"> </span><span class="n" id="mwB_Y">foo</span><span class="p" id="mwB_c">.</span><span class="na" id="mwB_g">printHello</span><span class="p" id="mwB_k">()</span> <span class="w" id="mwB_o"> </span><span class="c1" id="mwB_s">// With reflection</span> <span class="w" id="mwB_w"> </span><span class="k" id="mwB_0">try</span><span class="w" id="mwB_4"> </span><span class="p" id="mwB_8">{</span> <span class="w" id="mwCAA"> </span><span class="kd" id="mwCAE">val</span><span class="w" id="mwCAI"> </span><span class="nv" id="mwCAM">kClass</span><span class="w" id="mwCAQ"> </span><span class="o" id="mwCAU">=</span><span class="w" id="mwCAY"> </span><span class="n" id="mwCAc">Foo</span><span class="o" id="mwCAg">::</span><span class="kd" id="mwCAk">class</span> <span class="w" id="mwCAo"> </span><span class="nc" id="mwCAs">val</span><span class="w" id="mwCAw"> </span><span class="n" id="mwCA0">reflectedFoo</span><span class="w" id="mwCA4"> </span><span class="o" id="mwCA8">=</span><span class="w" id="mwCBA"> </span><span class="n" id="mwCBE">kClass</span><span class="p" id="mwCBI">.</span><span class="na" id="mwCBM">createInstance</span><span class="p" id="mwCBQ">()</span> <span class="w" id="mwCBU"> </span><span class="kd" id="mwCBY">val</span><span class="w" id="mwCBc"> </span><span class="nv" id="mwCBg">function</span><span class="w" id="mwCBk"> </span><span class="o" id="mwCBo">=</span><span class="w" id="mwCBs"> </span><span class="n" id="mwCBw">kClass</span><span class="p" id="mwCB0">.</span><span class="na" id="mwCB4">functions</span><span class="p" id="mwCB8">.</span><span class="na" id="mwCCA">first</span><span class="w" id="mwCCE"> </span><span class="p" id="mwCCI">{</span><span class="w" id="mwCCM"> </span><span class="nb" id="mwCCQ">it</span><span class="p" id="mwCCU">.</span><span class="na" id="mwCCY">name</span><span class="w" id="mwCCc"> </span><span class="o" id="mwCCg">==</span><span class="w" id="mwCCk"> </span><span class="s" id="mwCCo">"printHello"</span><span class="w" id="mwCCs"> </span><span class="p" id="mwCCw">}</span> <span class="w" id="mwCC0"> </span><span class="n" id="mwCC4">function</span><span class="p" id="mwCC8">.</span><span class="na" id="mwCDA">call</span><span class="p" id="mwCDE">(</span><span class="n" id="mwCDI">reflectedFoo</span><span class="p" id="mwCDM">)</span> <span class="w" id="mwCDQ"> </span><span class="p" id="mwCDU">}</span><span class="w" id="mwCDY"> </span><span class="k" id="mwCDc">catch</span><span class="w" id="mwCDg"> </span><span class="p" id="mwCDk">(</span><span class="n" id="mwCDo">e</span><span class="p" id="mwCDs">:</span><span class="w" id="mwCDw"> </span><span class="n" id="mwCD0">Exception</span><span class="p" id="mwCD4">)</span><span class="w" id="mwCD8"> </span><span class="p" id="mwCEA">{</span> <span class="w" id="mwCEE"> </span><span class="n" id="mwCEI">System</span><span class="p" id="mwCEM">.</span><span class="na" id="mwCEQ">err</span><span class="p" id="mwCEU">.</span><span class="na" id="mwCEY">printf</span><span class="p" id="mwCEc">(</span><span class="s" id="mwCEg">"An error occurred: %s%n"</span><span class="p" id="mwCEk">,</span><span class="w" id="mwCEo"> </span><span class="n" id="mwCEs">e</span><span class="p" id="mwCEw">.</span><span class="na" id="mwCE0">message</span><span class="p" id="mwCE4">)</span> <span class="w" id="mwCE8"> </span><span class="p" id="mwCFA">}</span> <span class="p" id="mwCFE">}</span>

Objective-C

The example below is in Objective-C, implying either the OpenStep or Foundation Kit framework is used:

<span id="mwCFk"></span><span class="c1" id="mwCFo">// Foo class.</span> <span class="k" id="mwCFs">@interface</span> <span class="nc" id="mwCFw">Foo</span> : <span class="bp" id="mwCF0">NSObject</span> <span class="p" id="mwCF4">-</span> <span class="p" id="mwCF8">(</span><span class="kt" id="mwCGA">void</span><span class="p" id="mwCGE">)</span><span class="nf" id="mwCGI">hello</span><span class="p" id="mwCGM">;</span> <span class="k" id="mwCGQ">@end</span> <span class="c1" id="mwCGU">// Sending "hello" to a Foo instance without reflection.</span> <span class="n" id="mwCGY">Foo</span><span class="o" id="mwCGc">*</span><span class="w" id="mwCGg"> </span><span class="n" id="mwCGk">obj</span><span class="w" id="mwCGo"> </span><span class="o" id="mwCGs">=</span><span class="w" id="mwCGw"> </span><span class="p" id="mwCG0">[[</span><span class="n" id="mwCG4">Foo</span><span class="w" id="mwCG8"> </span><span class="n" id="mwCHA">alloc</span><span class="p" id="mwCHE">]</span><span class="w" id="mwCHI"> </span><span class="n" id="mwCHM">init</span><span class="p" id="mwCHQ">];</span> <span class="p" id="mwCHU">[</span><span class="n" id="mwCHY">obj</span><span class="w" id="mwCHc"> </span><span class="n" id="mwCHg">hello</span><span class="p" id="mwCHk">];</span> <span class="c1" id="mwCHo">// Sending "hello" to a Foo instance with reflection.</span> <span class="kt" id="mwCHs">id</span><span class="w" id="mwCHw"> </span><span class="n" id="mwCH0">obj</span><span class="w" id="mwCH4"> </span><span class="o" id="mwCH8">=</span><span class="w" id="mwCIA"> </span><span class="p" id="mwCIE">[[</span><span class="n" id="mwCII">NSClassFromString</span><span class="p" id="mwCIM">(</span><span class="s" id="mwCIQ">@"Foo"</span><span class="p" id="mwCIU">)</span><span class="w" id="mwCIY"> </span><span class="n" id="mwCIc">alloc</span><span class="p" id="mwCIg">]</span><span class="w" id="mwCIk"> </span><span class="n" id="mwCIo">init</span><span class="p" id="mwCIs">];</span> <span class="p" id="mwCIw">[</span><span class="n" id="mwCI0">obj</span><span class="w" id="mwCI4"> </span><span class="n" id="mwCI8">performSelector</span><span class="o" id="mwCJA">:</span><span class="w" id="mwCJE"> </span><span class="k" id="mwCJI">@selector</span><span class="p" id="mwCJM">(</span><span class="n" id="mwCJQ">hello</span><span class="p" id="mwCJU">)];</span>

Perl

The example below is in Perl:

<span id="mwCJs"></span><span class="c1" id="mwCJw"># Without reflection</span> <span class="k" id="mwCJ0">my</span><span class="w" id="mwCJ4"> </span><span class="nv" id="mwCJ8">$foo</span><span class="w" id="mwCKA"> </span><span class="o" id="mwCKE">=</span><span class="w" id="mwCKI"> </span><span class="nn" id="mwCKM">Foo</span><span class="o" id="mwCKQ">-></span><span class="k" id="mwCKU">new</span><span class="p" id="mwCKY">;</span> <span class="nv" id="mwCKc">$foo</span><span class="o" id="mwCKg">-></span><span class="n" id="mwCKk">hello</span><span class="p" id="mwCKo">;</span> <span class="c1" id="mwCKs"># or</span> <span class="nn" id="mwCKw">Foo</span><span class="o" id="mwCK0">-></span><span class="k" id="mwCK4">new</span><span class="o" id="mwCK8">-></span><span class="n" id="mwCLA">hello</span><span class="p" id="mwCLE">;</span> <span class="c1" id="mwCLI"># With reflection</span> <span class="k" id="mwCLM">my</span><span class="w" id="mwCLQ"> </span><span class="nv" id="mwCLU">$class</span><span class="w" id="mwCLY"> </span><span class="o" id="mwCLc">=</span><span class="w" id="mwCLg"> </span><span class="s" id="mwCLk">"Foo"</span> <span class="k" id="mwCLo">my</span><span class="w" id="mwCLs"> </span><span class="nv" id="mwCLw">$constructor</span><span class="w" id="mwCL0"> </span><span class="o" id="mwCL4">=</span><span class="w" id="mwCL8"> </span><span class="s" id="mwCMA">"new"</span><span class="p" id="mwCME">;</span> <span class="k" id="mwCMI">my</span><span class="w" id="mwCMM"> </span><span class="nv" id="mwCMQ">$method</span><span class="w" id="mwCMU"> </span><span class="o" id="mwCMY">=</span><span class="w" id="mwCMc"> </span><span class="s" id="mwCMg">"hello"</span><span class="p" id="mwCMk">;</span> <span class="k" id="mwCMo">my</span><span class="w" id="mwCMs"> </span><span class="nv" id="mwCMw">$f</span><span class="w" id="mwCM0"> </span><span class="o" id="mwCM4">=</span><span class="w" id="mwCM8"> </span><span class="nv" id="mwCNA">$class</span><span class="o" id="mwCNE">-></span><span class="nv" id="mwCNI">$constructor</span><span class="p" id="mwCNM">;</span> <span class="nv" id="mwCNQ">$f</span><span class="o" id="mwCNU">-></span><span class="nv" id="mwCNY">$method</span><span class="p" id="mwCNc">;</span> <span class="c1" id="mwCNg"># or</span> <span class="nv" id="mwCNk">$class</span><span class="o" id="mwCNo">-></span><span class="nv" id="mwCNs">$constructor</span><span class="o" id="mwCNw">-></span><span class="nv" id="mwCN0">$method</span><span class="p" id="mwCN4">;</span> <span class="c1" id="mwCN8"># with eval</span> <span class="nb" id="mwCOA">eval</span><span class="w" id="mwCOE"> </span><span class="s" id="mwCOI">"new Foo->hello;"</span><span class="p" id="mwCOM">;</span>

PHP

The example below is in PHP:

<span id="mwCO0"></span><span class="c1" id="mwCO4">// Without reflection</span> <span class="nv" id="mwCO8">$foo</span> <span class="o" id="mwCPA">=</span> <span class="k" id="mwCPE">new</span> <span class="nx" id="mwCPI">Foo</span><span class="p" id="mwCPM">();</span> <span class="nv" id="mwCPQ">$foo</span><span class="o" id="mwCPU">-></span><span class="na" id="mwCPY">hello</span><span class="p" id="mwCPc">();</span> <span class="c1" id="mwCPg">// With reflection, using Reflections API</span> <span class="nv" id="mwCPk">$reflector</span> <span class="o" id="mwCPo">=</span> <span class="k" id="mwCPs">new</span> <span class="nx" id="mwCPw">ReflectionClass</span><span class="p" id="mwCP0">(</span><span class="s2" id="mwCP4">"Foo"</span><span class="p" id="mwCP8">);</span> <span class="nv" id="mwCQA">$foo</span> <span class="o" id="mwCQE">=</span> <span class="nv" id="mwCQI">$reflector</span><span class="o" id="mwCQM">-></span><span class="na" id="mwCQQ">newInstance</span><span class="p" id="mwCQU">();</span> <span class="nv" id="mwCQY">$hello</span> <span class="o" id="mwCQc">=</span> <span class="nv" id="mwCQg">$reflector</span><span class="o" id="mwCQk">-></span><span class="na" id="mwCQo">getMethod</span><span class="p" id="mwCQs">(</span><span class="s2" id="mwCQw">"hello"</span><span class="p" id="mwCQ0">);</span> <span class="nv" id="mwCQ4">$hello</span><span class="o" id="mwCQ8">-></span><span class="na" id="mwCRA">invoke</span><span class="p" id="mwCRE">(</span><span class="nv" id="mwCRI">$foo</span><span class="p" id="mwCRM">);</span>

Python

The example below is in Python:

<span id="mwCRk"></span><span class="kn" id="mwCRo">from</span><span class="w" id="mwCRs"> </span><span class="nn" id="mwCRw">typing</span><span class="w" id="mwCR0"> </span><span class="kn" id="mwCR4">import</span> <span class="n" id="mwCR8">Any</span> <span class="k" id="mwCSA">class</span><span class="w" id="mwCSE"> </span><span class="nc" id="mwCSI">Foo</span><span class="p" id="mwCSM">:</span> <span class="c1" id="mwCSQ"># ...</span> <span class="k" id="mwCSU">def</span><span class="w" id="mwCSY"> </span><span class="nf" id="mwCSc">print_hello</span><span class="p" id="mwCSg">(</span><span class="bp" id="mwCSk">self</span><span class="p" id="mwCSo">)</span> <span class="o" id="mwCSs">-></span> <span class="kc" id="mwCSw">None</span><span class="p" id="mwCS0">:</span> <span class="nb" id="mwCS4">print</span><span class="p" id="mwCS8">(</span><span class="s2" id="mwCTA">"Hello, world!"</span><span class="p" id="mwCTE">)</span> <span class="k" id="mwCTI">if</span> <span class="vm" id="mwCTM">__name__</span> <span class="o" id="mwCTQ">==</span> <span class="s2" id="mwCTU">"__main__"</span><span class="p" id="mwCTY">:</span> <span class="c1" id="mwCTc"># Without reflection</span> <span class="n" id="mwCTg">obj</span><span class="p" id="mwCTk">:</span> <span class="n" id="mwCTo">Foo</span> <span class="o" id="mwCTs">=</span> <span class="n" id="mwCTw">Foo</span><span class="p" id="mwCT0">()</span> <span class="n" id="mwCT4">obj</span><span class="o" id="mwCT8">.</span><span class="n" id="mwCUA">print_hello</span><span class="p" id="mwCUE">()</span> <span class="c1" id="mwCUI"># With reflection</span> <span class="n" id="mwCUM">obj</span><span class="p" id="mwCUQ">:</span> <span class="n" id="mwCUU">Foo</span> <span class="o" id="mwCUY">=</span> <span class="nb" id="mwCUc">globals</span><span class="p" id="mwCUg">()[</span><span class="s2" id="mwCUk">"Foo"</span><span class="p" id="mwCUo">]()</span> <span class="n" id="mwCUs">_</span><span class="p" id="mwCUw">:</span> <span class="n" id="mwCU0">Any</span> <span class="o" id="mwCU4">=</span> <span class="nb" id="mwCU8">getattr</span><span class="p" id="mwCVA">(</span><span class="n" id="mwCVE">obj</span><span class="p" id="mwCVI">,</span> <span class="s2" id="mwCVM">"print_hello"</span><span class="p" id="mwCVQ">)()</span> <span class="c1" id="mwCVU"># With eval</span> <span class="nb" id="mwCVY">eval</span><span class="p" id="mwCVc">(</span><span class="s2" id="mwCVg">"Foo().print_hello()"</span><span class="p" id="mwCVk">)</span>

R

The example below is in R:

<span id="mwCV8"></span><span class="c1" id="mwCWA"># Without reflection, assuming foo() returns an S3-type object that has method "hello"</span> <span class="n" id="mwCWE">obj</span><span class="w" id="mwCWI"> </span><span class="o" id="mwCWM"><-</span><span class="w" id="mwCWQ"> </span><span class="nf" id="mwCWU">foo</span><span class="p" id="mwCWY">()</span> <span class="nf" id="mwCWc">hello</span><span class="p" id="mwCWg">(</span><span class="n" id="mwCWk">obj</span><span class="p" id="mwCWo">)</span> <span class="c1" id="mwCWs"># With reflection</span> <span class="n" id="mwCWw">class_name</span><span class="w" id="mwCW0"> </span><span class="o" id="mwCW4"><-</span><span class="w" id="mwCW8"> </span><span class="s" id="mwCXA">"foo"</span> <span class="n" id="mwCXE">generic_having_foo_method</span><span class="w" id="mwCXI"> </span><span class="o" id="mwCXM"><-</span><span class="w" id="mwCXQ"> </span><span class="s" id="mwCXU">"hello"</span> <span class="n" id="mwCXY">obj</span><span class="w" id="mwCXc"> </span><span class="o" id="mwCXg"><-</span><span class="w" id="mwCXk"> </span><span class="nf" id="mwCXo">do.call</span><span class="p" id="mwCXs">(</span><span class="n" id="mwCXw">class_name</span><span class="p" id="mwCX0">,</span><span class="w" id="mwCX4"> </span><span class="nf" id="mwCX8">list</span><span class="p" id="mwCYA">())</span> <span class="nf" id="mwCYE">do.call</span><span class="p" id="mwCYI">(</span><span class="n" id="mwCYM">generic_having_foo_method</span><span class="p" id="mwCYQ">,</span><span class="w" id="mwCYU"> </span><span class="nf" id="mwCYY">alist</span><span class="p" id="mwCYc">(</span><span class="n" id="mwCYg">obj</span><span class="p" id="mwCYk">))</span>

Ruby

The example below is in Ruby:

<span id="mwCY8"></span><span class="c1" id="mwCZA"># Without reflection</span> <span class="n" id="mwCZE">obj</span><span class="w" id="mwCZI"> </span><span class="o" id="mwCZM">=</span><span class="w" id="mwCZQ"> </span><span class="no" id="mwCZU">Foo</span><span class="o" id="mwCZY">.</span><span class="n" id="mwCZc">new</span> <span class="n" id="mwCZg">obj</span><span class="o" id="mwCZk">.</span><span class="n" id="mwCZo">hello</span> <span class="c1" id="mwCZs"># With reflection</span> <span class="n" id="mwCZw">obj</span><span class="w" id="mwCZ0"> </span><span class="o" id="mwCZ4">=</span><span class="w" id="mwCZ8"> </span><span class="no" id="mwCaA">Object</span><span class="o" id="mwCaE">.</span><span class="n" id="mwCaI">const_get</span><span class="p" id="mwCaM">(</span><span class="s2" id="mwCaQ">"Foo"</span><span class="p" id="mwCaU">)</span><span class="o" id="mwCaY">.</span><span class="n" id="mwCac">new</span> <span class="n" id="mwCag">obj</span><span class="o" id="mwCak">.</span><span class="n" id="mwCao">send</span><span class="w" id="mwCas"> </span><span class="ss" id="mwCaw">:hello</span> <span class="c1" id="mwCa0"># With eval</span> <span class="nb" id="mwCa4">eval</span><span class="w" id="mwCa8"> </span><span class="s2" id="mwCbA">"Foo.new.hello"</span>

Rust

The example below is in Rust (using procedural macros).

<span id="mwCbc"></span><span class="c1" id="mwCbg">// A basic macro that registers a method name string to an actual method call</span> <span class="fm" id="mwCbk">macro_rules!</span><span class="w" id="mwCbo"> </span><span class="n" id="mwCbs">invoke_method</span><span class="w" id="mwCbw"> </span><span class="p" id="mwCb0">{</span> <span class="w" id="mwCb4"> </span><span class="p" id="mwCb8">(</span><span class="cp" id="mwCcA">$instance</span><span class="p" id="mwCcE">:</span><span class="nc" id="mwCcI">expr</span><span class="p" id="mwCcM">,</span><span class="w" id="mwCcQ"> </span><span class="cp" id="mwCcU">$method_name</span><span class="p" id="mwCcY">:</span><span class="nc" id="mwCcc">expr</span><span class="p" id="mwCcg">)</span><span class="w" id="mwCck"> </span><span class="o" id="mwCco">=></span><span class="w" id="mwCcs"> </span><span class="p" id="mwCcw">{</span> <span class="w" id="mwCc0"> </span><span class="k" id="mwCc4">match</span><span class="w" id="mwCc8"> </span><span class="cp" id="mwCdA">$method_name</span><span class="w" id="mwCdE"> </span><span class="p" id="mwCdI">{</span> <span class="w" id="mwCdM"> </span><span class="s" id="mwCdQ">"print_hello"</span><span class="w" id="mwCdU"> </span><span class="o" id="mwCdY">=></span><span class="w" id="mwCdc"> </span><span class="cp" id="mwCdg">$instance</span><span class="p" id="mwCdk">.</span><span class="n" id="mwCdo">print_hello</span><span class="p" id="mwCds">(),</span> <span class="w" id="mwCdw"> </span><span class="n" id="mwCd0">_</span><span class="w" id="mwCd4"> </span><span class="o" id="mwCd8">=></span><span class="w" id="mwCeA"> </span><span class="fm" id="mwCeE">eprintln!</span><span class="p" id="mwCeI">(</span><span class="s" id="mwCeM">"An error occurred: Method not found."</span><span class="p" id="mwCeQ">),</span> <span class="w" id="mwCeU"> </span><span class="p" id="mwCeY">}</span> <span class="w" id="mwCec"> </span><span class="p" id="mwCeg">};</span> <span class="p" id="mwCek">}</span> <span class="k" id="mwCeo">struct</span><span class="w" id="mwCes"> </span><span class="nc" id="mwCew">Foo</span><span class="p" id="mwCe0">;</span> <span class="k" id="mwCe4">impl</span><span class="w" id="mwCe8"> </span><span class="n" id="mwCfA">Foo</span><span class="w" id="mwCfE"> </span><span class="p" id="mwCfI">{</span> <span class="w" id="mwCfM"> </span><span class="k" id="mwCfQ">fn</span><span class="w" id="mwCfU"> </span><span class="nf" id="mwCfY">print_hello</span><span class="p" id="mwCfc">(</span><span class="o" id="mwCfg">&</span><span class="bp" id="mwCfk">self</span><span class="p" id="mwCfo">)</span><span class="w" id="mwCfs"> </span><span class="p" id="mwCfw">{</span> <span class="w" id="mwCf0"> </span><span class="fm" id="mwCf4">println!</span><span class="p" id="mwCf8">(</span><span class="s" id="mwCgA">"Hello, world!"</span><span class="p" id="mwCgE">);</span> <span class="w" id="mwCgI"> </span><span class="p" id="mwCgM">}</span> <span class="p" id="mwCgQ">}</span> <span class="k" id="mwCgU">fn</span><span class="w" id="mwCgY"> </span><span class="nf" id="mwCgc">main</span><span class="p" id="mwCgg">()</span><span class="w" id="mwCgk"> </span><span class="p" id="mwCgo">{</span> <span class="w" id="mwCgs"> </span><span class="kd" id="mwCgw">let</span><span class="w" id="mwCg0"> </span><span class="n" id="mwCg4">foo</span><span class="w" id="mwCg8"> </span><span class="o" id="mwChA">=</span><span class="w" id="mwChE"> </span><span class="n" id="mwChI">Foo</span><span class="p" id="mwChM">;</span> <span class="w" id="mwChQ"> </span><span class="c1" id="mwChU">// Normal call sequence</span> <span class="w" id="mwChY"> </span><span class="n" id="mwChc">foo</span><span class="p" id="mwChg">.</span><span class="n" id="mwChk">print_hello</span><span class="p" id="mwCho">();</span> <span class="w" id="mwChs"> </span><span class="c1" id="mwChw">// Reflection-style sequence via compile-time mapping</span> <span class="w" id="mwCh0"> </span><span class="kd" id="mwCh4">let</span><span class="w" id="mwCh8"> </span><span class="n" id="mwCiA">method_to_call</span><span class="w" id="mwCiE"> </span><span class="o" id="mwCiI">=</span><span class="w" id="mwCiM"> </span><span class="s" id="mwCiQ">"print_hello"</span><span class="p" id="mwCiU">;</span> <span class="w" id="mwCiY"> </span><span class="n" id="mwCic">invoke_method</span><span class="o" id="mwCig">!</span><span class="p" id="mwCik">(</span><span class="n" id="mwCio">foo</span><span class="p" id="mwCis">,</span><span class="w" id="mwCiw"> </span><span class="n" id="mwCi0">method_to_call</span><span class="p" id="mwCi4">);</span> <span class="p" id="mwCi8">}</span>

Swift

Swift reflection is read-only, and thus dynamic invocation is only possible through Objective-C.

<span id="mwCjY"></span><span class="kd" id="mwCjc">import</span><span class="w" id="mwCjg"> </span><span class="nc" id="mwCjk">Foundation</span> <span class="kd" id="mwCjo">class</span><span class="w" id="mwCjs"> </span><span class="nc" id="mwCjw">Foo</span><span class="p" id="mwCj0">:</span><span class="w" id="mwCj4"> </span><span class="bp" id="mwCj8">NSObject</span><span class="w" id="mwCkA"> </span><span class="p" id="mwCkE">{</span> <span class="w" id="mwCkI"> </span><span class="kr" id="mwCkM">@objc</span><span class="w" id="mwCkQ"> </span><span class="kd" id="mwCkU">func</span><span class="w" id="mwCkY"> </span><span class="nf" id="mwCkc">printHello</span><span class="p" id="mwCkg">()</span><span class="w" id="mwCkk"> </span><span class="p" id="mwCko">{</span> <span class="w" id="mwCks"> </span><span class="bp" id="mwCkw">print</span><span class="p" id="mwCk0">(</span><span class="s" id="mwCk4">"Hello, world!"</span><span class="p" id="mwCk8">)</span> <span class="w" id="mwClA"> </span><span class="p" id="mwClE">}</span> <span class="p" id="mwClI">}</span> <span class="kd" id="mwClM">class</span><span class="w" id="mwClQ"> </span><span class="nc" id="mwClU">InvokeFooExample</span><span class="w" id="mwClY"> </span><span class="p" id="mwClc">{</span> <span class="w" id="mwClg"> </span><span class="kd" id="mwClk">static</span><span class="w" id="mwClo"> </span><span class="kd" id="mwCls">func</span><span class="w" id="mwClw"> </span><span class="nf" id="mwCl0">main</span><span class="p" id="mwCl4">()</span><span class="w" id="mwCl8"> </span><span class="p" id="mwCmA">{</span> <span class="w" id="mwCmE"> </span><span class="c1" id="mwCmI">// Without reflection</span> <span class="w" id="mwCmM"> </span><span class="kd" id="mwCmQ">let</span><span class="w" id="mwCmU"> </span><span class="nv" id="mwCmY">foo</span><span class="w" id="mwCmc"> </span><span class="p" id="mwCmg">=</span><span class="w" id="mwCmk"> </span><span class="n" id="mwCmo">Foo</span><span class="p" id="mwCms">()</span> <span class="w" id="mwCmw"> </span><span class="n" id="mwCm0">foo</span><span class="p" id="mwCm4">.</span><span class="n" id="mwCm8">printHello</span><span class="p" id="mwCnA">()</span> <span class="w" id="mwCnE"> </span><span class="c1" id="mwCnI">// With "reflection" (Objective-C runtime)</span> <span class="w" id="mwCnM"> </span><span class="kd" id="mwCnQ">let</span><span class="w" id="mwCnU"> </span><span class="nv" id="mwCnY">reflectedFoo</span><span class="w" id="mwCnc"> </span><span class="p" id="mwCng">=</span><span class="w" id="mwCnk"> </span><span class="n" id="mwCno">Foo</span><span class="p" id="mwCns">()</span> <span class="w" id="mwCnw"> </span><span class="kd" id="mwCn0">let</span><span class="w" id="mwCn4"> </span><span class="nv" id="mwCn8">selector</span><span class="w" id="mwCoA"> </span><span class="p" id="mwCoE">=</span><span class="w" id="mwCoI"> </span><span class="k" id="mwCoM">#selector</span><span class="p" id="mwCoQ">(</span><span class="n" id="mwCoU">Foo</span><span class="p" id="mwCoY">.</span><span class="n" id="mwCoc">printHello</span><span class="p" id="mwCog">)</span> <span class="w" id="mwCok"> </span><span class="k" id="mwCoo">if</span><span class="w" id="mwCos"> </span><span class="n" id="mwCow">reflectedFoo</span><span class="p" id="mwCo0">.</span><span class="n" id="mwCo4">responds</span><span class="p" id="mwCo8">(</span><span class="n" id="mwCpA">to</span><span class="p" id="mwCpE">:</span><span class="w" id="mwCpI"> </span><span class="n" id="mwCpM">selector</span><span class="p" id="mwCpQ">)</span><span class="w" id="mwCpU"> </span><span class="p" id="mwCpY">{</span> <span class="w" id="mwCpc"> </span><span class="n" id="mwCpg">reflectedFoo</span><span class="p" id="mwCpk">.</span><span class="n" id="mwCpo">perform</span><span class="p" id="mwCps">(</span><span class="n" id="mwCpw">selector</span><span class="p" id="mwCp0">)</span> <span class="w" id="mwCp4"> </span><span class="p" id="mwCp8">}</span> <span class="w" id="mwCqA"> </span><span class="p" id="mwCqE">}</span> <span class="p" id="mwCqI">}</span>

Swift's reflection system, with Swift.Mirror, is much more limited in scope:

<span id="mwCqc"></span><span class="kd" id="mwCqg">import</span><span class="w" id="mwCqk"> </span><span class="nc" id="mwCqo">Foundation</span> <span class="kd" id="mwCqs">class</span><span class="w" id="mwCqw"> </span><span class="nc" id="mwCq0">Foo</span><span class="w" id="mwCq4"> </span><span class="p" id="mwCq8">{</span> <span class="w" id="mwCrA"> </span><span class="kd" id="mwCrE">func</span><span class="w" id="mwCrI"> </span><span class="nf" id="mwCrM">printHello</span><span class="p" id="mwCrQ">()</span><span class="w" id="mwCrU"> </span><span class="p" id="mwCrY">{</span> <span class="w" id="mwCrc"> </span><span class="bp" id="mwCrg">print</span><span class="p" id="mwCrk">(</span><span class="s" id="mwCro">"Hello, world!"</span><span class="p" id="mwCrs">)</span> <span class="w" id="mwCrw"> </span><span class="p" id="mwCr0">}</span> <span class="p" id="mwCr4">}</span> <span class="kd" id="mwCr8">let</span><span class="w" id="mwCsA"> </span><span class="nv" id="mwCsE">foo</span><span class="w" id="mwCsI"> </span><span class="p" id="mwCsM">=</span><span class="w" id="mwCsQ"> </span><span class="n" id="mwCsU">Foo</span><span class="p" id="mwCsY">()</span> <span class="kd" id="mwCsc">let</span><span class="w" id="mwCsg"> </span><span class="nv" id="mwCsk">mirror</span><span class="w" id="mwCso"> </span><span class="p" id="mwCss">=</span><span class="w" id="mwCsw"> </span><span class="n" id="mwCs0">Mirror</span><span class="p" id="mwCs4">(</span><span class="n" id="mwCs8">reflecting</span><span class="p" id="mwCtA">:</span><span class="w" id="mwCtE"> </span><span class="n" id="mwCtI">foo</span><span class="p" id="mwCtM">)</span> <span class="bp" id="mwCtQ">print</span><span class="p" id="mwCtU">(</span><span class="n" id="mwCtY">type</span><span class="p" id="mwCtc">(</span><span class="n" id="mwCtg">of</span><span class="p" id="mwCtk">:</span><span class="w" id="mwCto"> </span><span class="n" id="mwCts">foo</span><span class="p" id="mwCtw">))</span><span class="w" id="mwCt0"> </span><span class="c1" id="mwCt4">// Foo</span> <span class="bp" id="mwCt8">print</span><span class="p" id="mwCuA">(</span><span class="n" id="mwCuE">mirror</span><span class="p" id="mwCuI">.</span><span class="n" id="mwCuM">children</span><span class="p" id="mwCuQ">.</span><span class="bp" id="mwCuU">count</span><span class="p" id="mwCuY">)</span><span class="w" id="mwCuc"> </span><span class="c1" id="mwCug">// Properties only</span>

Xojo

The following is an example using Xojo:

<span id="mwCu4"></span><span class="c" id="mwCu8">' Without reflection</span> <span class="k" id="mwCvA">Dim</span><span class="w" id="mwCvE"> </span><span class="n" id="mwCvI">fooInstance</span><span class="w" id="mwCvM"> </span><span class="ow" id="mwCvQ">As</span><span class="w" id="mwCvU"> </span><span class="k" id="mwCvY">New</span><span class="w" id="mwCvc"> </span><span class="n" id="mwCvg">Foo</span> <span class="n" id="mwCvk">fooInstance</span><span class="p" id="mwCvo">.</span><span class="n" id="mwCvs">PrintHello</span> <span class="c" id="mwCvw">' With reflection</span> <span class="k" id="mwCv0">Dim</span><span class="w" id="mwCv4"> </span><span class="n" id="mwCv8">classInfo</span><span class="w" id="mwCwA"> </span><span class="ow" id="mwCwE">As</span><span class="w" id="mwCwI"> </span><span class="n" id="mwCwM">Introspection</span><span class="p" id="mwCwQ">.</span><span class="n" id="mwCwU">Typeinfo</span><span class="w" id="mwCwY"> </span><span class="o" id="mwCwc">=</span><span class="w" id="mwCwg"> </span><span class="n" id="mwCwk">GetTypeInfo</span><span class="p" id="mwCwo">(</span><span class="n" id="mwCws">Foo</span><span class="p" id="mwCww">)</span> <span class="k" id="mwCw0">Dim</span><span class="w" id="mwCw4"> </span><span class="n" id="mwCw8">constructors</span><span class="p" id="mwCxA">()</span><span class="w" id="mwCxE"> </span><span class="ow" id="mwCxI">As</span><span class="w" id="mwCxM"> </span><span class="n" id="mwCxQ">Introspection</span><span class="p" id="mwCxU">.</span><span class="n" id="mwCxY">ConstructorInfo</span><span class="w" id="mwCxc"> </span><span class="o" id="mwCxg">=</span><span class="w" id="mwCxk"> </span><span class="n" id="mwCxo">classInfo</span><span class="p" id="mwCxs">.</span><span class="n" id="mwCxw">GetConstructors</span> <span class="k" id="mwCx0">Dim</span><span class="w" id="mwCx4"> </span><span class="n" id="mwCx8">fooInstance</span><span class="w" id="mwCyA"> </span><span class="ow" id="mwCyE">As</span><span class="w" id="mwCyI"> </span><span class="n" id="mwCyM">Foo</span><span class="w" id="mwCyQ"> </span><span class="o" id="mwCyU">=</span><span class="w" id="mwCyY"> </span><span class="n" id="mwCyc">constructors</span><span class="p" id="mwCyg">(</span><span class="mi" id="mwCyk">0</span><span class="p" id="mwCyo">).</span><span class="n" id="mwCys">Invoke</span> <span class="k" id="mwCyw">Dim</span><span class="w" id="mwCy0"> </span><span class="n" id="mwCy4">methods</span><span class="p" id="mwCy8">()</span><span class="w" id="mwCzA"> </span><span class="ow" id="mwCzE">As</span><span class="w" id="mwCzI"> </span><span class="n" id="mwCzM">Introspection</span><span class="p" id="mwCzQ">.</span><span class="n" id="mwCzU">MethodInfo</span><span class="w" id="mwCzY"> </span><span class="o" id="mwCzc">=</span><span class="w" id="mwCzg"> </span><span class="n" id="mwCzk">classInfo</span><span class="p" id="mwCzo">.</span><span class="n" id="mwCzs">GetMethods</span> <span class="k" id="mwCzw">For</span><span class="w" id="mwCz0"> </span><span class="k" id="mwCz4">Each</span><span class="w" id="mwCz8"> </span><span class="n" id="mwC0A">m</span><span class="w" id="mwC0E"> </span><span class="ow" id="mwC0I">As</span><span class="w" id="mwC0M"> </span><span class="n" id="mwC0Q">Introspection</span><span class="p" id="mwC0U">.</span><span class="n" id="mwC0Y">MethodInfo</span><span class="w" id="mwC0c"> </span><span class="ow" id="mwC0g">In</span><span class="w" id="mwC0k"> </span><span class="n" id="mwC0o">methods</span> <span class="w" id="mwC0s"> </span><span class="k" id="mwC0w">If</span><span class="w" id="mwC00"> </span><span class="n" id="mwC04">m</span><span class="p" id="mwC08">.</span><span class="n" id="mwC1A">Name</span><span class="w" id="mwC1E"> </span><span class="o" id="mwC1I">=</span><span class="w" id="mwC1M"> </span><span class="s" id="mwC1Q">"PrintHello"</span><span class="w" id="mwC1U"> </span><span class="k" id="mwC1Y">Then</span> <span class="w" id="mwC1c"> </span><span class="n" id="mwC1g">m</span><span class="p" id="mwC1k">.</span><span class="n" id="mwC1o">Invoke</span><span class="p" id="mwC1s">(</span><span class="n" id="mwC1w">fooInstance</span><span class="p" id="mwC10">)</span> <span class="w" id="mwC14"> </span><span class="k" id="mwC18">End</span><span class="w" id="mwC2A"> </span><span class="k" id="mwC2E">If</span> <span class="k" id="mwC2I">Next</span>

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