| <html lang="en"> |
| <head> |
| <title>Dynamically registering methods - Using the GNU Compiler Collection (GCC)</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="Using the GNU Compiler Collection (GCC)"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Messaging-with-the-GNU-Objective_002dC-runtime.html#Messaging-with-the-GNU-Objective_002dC-runtime" title="Messaging with the GNU Objective-C runtime"> |
| <link rel="next" href="Forwarding-hook.html#Forwarding-hook" title="Forwarding hook"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| Copyright (C) 1988-2013 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being ``Funding Free Software'', the Front-Cover |
| Texts being (a) (see below), and with the Back-Cover Texts being (b) |
| (see below). A copy of the license is included in the section entitled |
| ``GNU Free Documentation License''. |
| |
| (a) The FSF's Front-Cover Text is: |
| |
| A GNU Manual |
| |
| (b) The FSF's Back-Cover Text is: |
| |
| You have freedom to copy and modify this GNU Manual, like GNU |
| software. Copies published by the Free Software Foundation raise |
| funds for GNU development.--> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="Dynamically-registering-methods"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Forwarding-hook.html#Forwarding-hook">Forwarding hook</a>, |
| Up: <a rel="up" accesskey="u" href="Messaging-with-the-GNU-Objective_002dC-runtime.html#Messaging-with-the-GNU-Objective_002dC-runtime">Messaging with the GNU Objective-C runtime</a> |
| <hr> |
| </div> |
| |
| <h4 class="subsection">8.10.1 Dynamically registering methods</h4> |
| |
| <p>If <code>objc_msg_lookup()</code> does not find a suitable method |
| implementation, because the receiver does not implement the required |
| method, it tries to see if the class can dynamically register the |
| method. |
| |
| <p>To do so, the runtime checks if the class of the receiver implements |
| the method |
| |
| <pre class="smallexample"> + (BOOL) resolveInstanceMethod: (SEL)selector; |
| </pre> |
| <p>in the case of an instance method, or |
| |
| <pre class="smallexample"> + (BOOL) resolveClassMethod: (SEL)selector; |
| </pre> |
| <p>in the case of a class method. If the class implements it, the |
| runtime invokes it, passing as argument the selector of the original |
| method, and if it returns <code>YES</code>, the runtime tries the lookup |
| again, which could now succeed if a matching method was added |
| dynamically by <code>+resolveInstanceMethod:</code> or |
| <code>+resolveClassMethod:</code>. |
| |
| <p>This allows classes to dynamically register methods (by adding them to |
| the class using <code>class_addMethod</code>) when they are first called. |
| To do so, a class should implement <code>+resolveInstanceMethod:</code> (or, |
| depending on the case, <code>+resolveClassMethod:</code>) and have it |
| recognize the selectors of methods that can be registered dynamically |
| at runtime, register them, and return <code>YES</code>. It should return |
| <code>NO</code> for methods that it does not dynamically registered at |
| runtime. |
| |
| <p>If <code>+resolveInstanceMethod:</code> (or <code>+resolveClassMethod:</code>) is |
| not implemented or returns <code>NO</code>, the runtime then tries the |
| forwarding hook. |
| |
| <p>Support for <code>+resolveInstanceMethod:</code> and |
| <code>resolveClassMethod:</code> was added to the GNU Objective-C runtime in |
| GCC version 4.6. |
| |
| <!-- ========================================================================= --> |
| </body></html> |
| |
