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126 lines
5.5 KiB
HTML
126 lines
5.5 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2018 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Dynamically registering methods (Using the GNU Compiler Collection (GCC))</title>
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<meta name="description" content="Dynamically registering methods (Using the GNU Compiler Collection (GCC))">
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<meta name="keywords" content="Dynamically registering methods (Using the GNU Compiler Collection (GCC))">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Messaging-with-the-GNU-Objective_002dC-runtime.html#Messaging-with-the-GNU-Objective_002dC-runtime" rel="up" title="Messaging with the GNU Objective-C runtime">
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<link href="Forwarding-hook.html#Forwarding-hook" rel="next" title="Forwarding hook">
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<link href="Messaging-with-the-GNU-Objective_002dC-runtime.html#Messaging-with-the-GNU-Objective_002dC-runtime" rel="prev" title="Messaging with the GNU Objective-C runtime">
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<style type="text/css">
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Dynamically-registering-methods"></a>
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<div class="header">
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<p>
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Next: <a href="Forwarding-hook.html#Forwarding-hook" accesskey="n" rel="next">Forwarding hook</a>, Up: <a href="Messaging-with-the-GNU-Objective_002dC-runtime.html#Messaging-with-the-GNU-Objective_002dC-runtime" accesskey="u" rel="up">Messaging with the GNU Objective-C runtime</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Dynamically-Registering-Methods"></a>
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<h4 class="subsection">8.10.1 Dynamically Registering Methods</h4>
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<p>If <code>objc_msg_lookup()</code> does not find a suitable method
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implementation, because the receiver does not implement the required
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method, it tries to see if the class can dynamically register the
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method.
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</p>
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<p>To do so, the runtime checks if the class of the receiver implements
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the method
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</p>
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<div class="smallexample">
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<pre class="smallexample">+ (BOOL) resolveInstanceMethod: (SEL)selector;
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</pre></div>
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<p>in the case of an instance method, or
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</p>
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<div class="smallexample">
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<pre class="smallexample">+ (BOOL) resolveClassMethod: (SEL)selector;
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</pre></div>
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<p>in the case of a class method. If the class implements it, the
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runtime invokes it, passing as argument the selector of the original
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method, and if it returns <code>YES</code>, the runtime tries the lookup
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again, which could now succeed if a matching method was added
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dynamically by <code>+resolveInstanceMethod:</code> or
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<code>+resolveClassMethod:</code>.
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</p>
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<p>This allows classes to dynamically register methods (by adding them to
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the class using <code>class_addMethod</code>) when they are first called.
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To do so, a class should implement <code>+resolveInstanceMethod:</code> (or,
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depending on the case, <code>+resolveClassMethod:</code>) and have it
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recognize the selectors of methods that can be registered dynamically
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at runtime, register them, and return <code>YES</code>. It should return
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<code>NO</code> for methods that it does not dynamically registered at
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runtime.
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</p>
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<p>If <code>+resolveInstanceMethod:</code> (or <code>+resolveClassMethod:</code>) is
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not implemented or returns <code>NO</code>, the runtime then tries the
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forwarding hook.
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</p>
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<p>Support for <code>+resolveInstanceMethod:</code> and
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<code>resolveClassMethod:</code> was added to the GNU Objective-C runtime in
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GCC version 4.6.
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</p>
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</body>
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</html>
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