118 lines
9.3 KiB
HTML
118 lines
9.3 KiB
HTML
<!DOCTYPE html>
|
|
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
|
|
<head><meta http-equiv="x-ua-compatible" content="ie=edge">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<title>std::get_deleter</title>
|
|
<link rel="stylesheet" href="ext.css" />
|
|
<link rel="stylesheet" href="site_modules.css" />
|
|
</head>
|
|
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_memory_shared_ptr_get_deleter skin-cppreference2 action-view cpp-navbar">
|
|
<div id="cpp-content-base">
|
|
<div id="content"><a id="top"></a>
|
|
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::</span>get_deleter</h1>
|
|
<div id="bodyContent">
|
|
<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-memory.html">memory</a>‎ | <a href="cpp-memory-shared_ptr.html">shared ptr</a></span></div>
|
|
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
|
|
<table class="t-dcl-begin">
|
|
<tbody>
|
|
<tr class="t-dsc-header">
|
|
<td>
|
|
<div>定义于头文件 <code><a href="cpp-header-memory.html"><memory></a></code></div>
|
|
</td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
<tr class="t-dcl t-since-cxx11">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Deleter, <span class="kw1">class</span> T <span class="sy1">></span><br />
|
|
Deleter<span class="sy2">*</span> get_deleter<span class="br0">(</span> <span class="kw4">const</span> <a href="cpp-memory-shared_ptr.html"><span class="kw734">std::<span class="me2">shared_ptr</span></span></a><span class="sy1"><</span>T<span class="sy1">></span><span class="sy3">&</span> p <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>访问 <code>p</code> 的删除器。若共享指针 <code>p</code> 占有无 cv 限定 <code>Deleter</code> 类型的删除器（例如，若以接收删除器为参数的构造函数之一创建它），则返回指向删除器的指针。否则，返回空指针。</p>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
|
|
<table class="t-par-begin">
|
|
<tr class="t-par">
|
|
<td>p</td>
|
|
<td>-</td>
|
|
<td>需要访问其删除器的共享指针</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
|
<p>指向被占有删除器的指针或 <code>nullptr</code> 。只要至少还有一个 <code>shared_ptr</code> 实例占有返回的指针，它就合法。</p>
|
|
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
|
|
<p>返回的指针可能比最后一个 <code>shared_ptr</code> 的生存期更持久，例如，还剩下 <span class="t-lc"><a href="cpp-memory-weak_ptr.html">std::weak_ptr</a></span> 时且实现在销毁整个控制块前不销毁删除器。</p>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-example">
|
|
<p>演示 shared_ptr 删除器独立于 shared_ptr 的类型</p>
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <iostream></span>
|
|
<span class="co2">#include <memory></span>
|
|
|
|
<span class="kw1">struct</span> Foo <span class="br0">{</span> <span class="kw4">int</span> i<span class="sy4">;</span> <span class="br0">}</span><span class="sy4">;</span>
|
|
<span class="kw4">void</span> foo_deleter<span class="br0">(</span>Foo <span class="sy2">*</span> p<span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"foo_deleter called!<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
delete p<span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-memory-shared_ptr.html"><span class="kw734">std::<span class="me2">shared_ptr</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> aptr<span class="sy4">;</span>
|
|
|
|
<span class="br0">{</span>
|
|
<span class="co1">// 创建拥有一个 Foo 和删除器的 shared_ptr</span>
|
|
<span class="kw4">auto</span> foo_p <span class="sy1">=</span> new Foo<span class="sy4">;</span>
|
|
<a href="cpp-memory-shared_ptr.html"><span class="kw734">std::<span class="me2">shared_ptr</span></span></a><span class="sy1"><</span>Foo<span class="sy1">></span> r<span class="br0">(</span>foo_p, foo_deleter<span class="br0">)</span><span class="sy4">;</span>
|
|
aptr <span class="sy1">=</span> <a href="cpp-memory-shared_ptr.html"><span class="kw734">std::<span class="me2">shared_ptr</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span><span class="br0">(</span>r, <span class="sy3">&</span>r<span class="sy2">-</span><span class="sy1">></span>i<span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 别名使用构造函数</span>
|
|
<span class="co1">// aptr 现在指向 int ，但管理整个 Foo</span>
|
|
<span class="br0">}</span> <span class="co1">// r 被销毁（不调用删除器）</span>
|
|
|
|
<span class="co1">// 获得指向删除器的指针：</span>
|
|
<span class="kw1">if</span><span class="br0">(</span><span class="kw4">auto</span> del_p <span class="sy1">=</span> std<span class="sy4">::</span><span class="me2">get_deleter</span><span class="sy1"><</span><span class="kw4">void</span><span class="br0">(</span><span class="sy2">*</span><span class="br0">)</span><span class="br0">(</span>Foo<span class="sy2">*</span><span class="br0">)</span><span class="sy1">></span><span class="br0">(</span>aptr<span class="br0">)</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"shared_ptr<int> owns a deleter<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
<span class="kw1">if</span><span class="br0">(</span><span class="sy2">*</span>del_p <span class="sy1">==</span> foo_deleter<span class="br0">)</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"...and it equals &foo_deleter<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
<span class="br0">}</span> <span class="kw1">else</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"The deleter of shared_ptr<int> is null!<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
<span class="br0">}</span> <span class="co1">// 于此调用删除器</span></pre></div>
|
|
</div>
|
|
<p>输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">shared_ptr<int> owns a deleter
|
|
...and it equals &foo_deleter
|
|
foo_deleter called!</pre></div>
|
|
</div>
|
|
</div>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div t-dsc-member-nobold-div">
|
|
<div><a href="cpp-memory-shared_ptr-shared_ptr.html"><span class="t-lines"><span>(构造函数)</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td><span class="t-lc"><a href="cpp-memory-shared_ptr.html">std::shared_ptr</a></span> 构造函数<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|