mirror of
https://github.com/php/doc-zh.git
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134 lines
3.7 KiB
XML
134 lines
3.7 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<!-- EN-Revision: c4650e160398873696e59305a11db9645e0b7304 Maintainer: mowangjuanzi Status: ready -->
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<!-- CREDITS: Luffy -->
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<reference xml:id="class.weakmap" role="class" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude">
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<title>WeakMap 类</title>
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<titleabbrev>WeakMap</titleabbrev>
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<partintro>
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<!-- {{{ WeakMap intro -->
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<section xml:id="weakmap.intro">
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&reftitle.intro;
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<para>
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<classname>WeakMap</classname> 是将对象作为 key 来访问的 map（或者说字典）。然而，与其它类似 <classname>SplObjectStorage</classname>
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不同，<classname>WeakMap</classname> 中的对象 key 不影响对象的引用计数。也就是说，如果在任何时候对其唯一的剩余引用是
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<classname>WeakMap</classname> key，那么该对象将会被垃圾收集并从 <classname>WeakMap</classname>
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移除。它的主要用法是从对象中编译数据派生缓存，这种场景下不需要存活得比对象更久。
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</para>
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<para>
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<classname>WeakMap</classname> 实现了 <interfacename>ArrayAccess</interfacename>、
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<interfacename>Traversable</interfacename>（通过 <interfacename>IteratorAggregate</interfacename>）和
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<interfacename>Countable</interfacename>，
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因此大多数情况下，它能和关联数组一样使用。
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</para>
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</section>
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<!-- }}} -->
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<section xml:id="weakmap.synopsis">
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&reftitle.classsynopsis;
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<!-- {{{ Synopsis -->
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<classsynopsis class="class">
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<ooclass>
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<modifier>final</modifier>
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<classname>WeakMap</classname>
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</ooclass>
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<oointerface>
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<modifier>implements</modifier>
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<interfacename>ArrayAccess</interfacename>
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</oointerface>
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<oointerface>
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<interfacename>Countable</interfacename>
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</oointerface>
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<oointerface>
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<interfacename>IteratorAggregate</interfacename>
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</oointerface>
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<classsynopsisinfo role="comment">&Methods;</classsynopsisinfo>
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<xi:include xpointer="xmlns(db=http://docbook.org/ns/docbook) xpointer(id('class.weakmap')/db:refentry/db:refsect1[@role='description']/descendant::db:methodsynopsis[@role='WeakMap'])">
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<xi:fallback/>
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</xi:include>
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</classsynopsis>
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<!-- }}} -->
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</section>
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<!-- {{{ weakmap examples -->
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<section xml:id="weakmap.examples">
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&reftitle.examples;
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<para>
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<example>
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<title><classname>Weakmap</classname> 用法示例</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$wm = new WeakMap();
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$o = new stdClass;
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class A {
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public function __destruct() {
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echo "Dead!\n";
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}
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}
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$wm[$o] = new A;
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var_dump(count($wm));
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echo "Unsetting...\n";
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unset($o);
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echo "Done\n";
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var_dump(count($wm));
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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int(1)
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Unsetting...
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Dead!
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Done
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int(0)
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]]>
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</screen>
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</example>
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</para>
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</section>
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<!-- }}} -->
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</partintro>
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&language.predefined.weakmap.count;
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&language.predefined.weakmap.getiterator;
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&language.predefined.weakmap.offsetexists;
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&language.predefined.weakmap.offsetget;
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&language.predefined.weakmap.offsetset;
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&language.predefined.weakmap.offsetunset;
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</reference>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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