119 lines
10 KiB
HTML
119 lines
10 KiB
HTML
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<title>std::shared_ptr<T>::operator=</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_memory_shared_ptr_operator skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::shared_ptr<T>::</span>operator=</h1>
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<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>
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<div><span class="mw-geshi cpp source-cpp">shared_ptr<span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> shared_ptr<span class="sy3">&</span> r <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Y <span class="sy1">></span><br />
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shared_ptr<span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> shared_ptr<span class="sy1"><</span>Y<span class="sy1">></span><span class="sy3">&</span> r <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
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<div><span class="mw-geshi cpp source-cpp">shared_ptr<span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> shared_ptr<span class="sy3">&&</span> r <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Y <span class="sy1">></span><br />
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shared_ptr<span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> shared_ptr<span class="sy1"><</span>Y<span class="sy1">></span><span class="sy3">&&</span> r <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td>(2)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Y <span class="sy1">></span><br />
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shared_ptr<span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> <a href="cpp-memory-auto_ptr.html"><span class="kw742">std::<span class="me2">auto_ptr</span></span></a><span class="sy1"><</span>Y<span class="sy1">></span><span class="sy3">&&</span> r <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(3)</td>
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<td><span class="t-mark">(C++11 中弃用)</span><br />
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<span class="t-mark-rev t-until-cxx17">(C++17 中移除)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Y, <span class="kw1">class</span> Deleter <span class="sy1">></span><br />
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shared_ptr<span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> <a href="cpp-memory-unique_ptr.html"><span class="kw733">std::<span class="me2">unique_ptr</span></span></a><span class="sy1"><</span>Y,Deleter<span class="sy1">></span><span class="sy3">&&</span> r <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(4)</td>
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<td></td>
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<td></td>
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<p>以 <code>r</code> 所管理者替换被管理对象。</p>
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<p>若 <code>*this</code> 已占有对象且它是最后一个占有该对象的 <code>shared_ptr</code> ，且 <code>r</code> 与 <code>*this</code> 不相同，则通过占有的删除器销毁对象。</p>
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<div class="t-li1"><span class="t-li">1)</span> 共享 <code>r</code> 所管理对象的所有权。若 <code>r</code> 不管理对象，则 <code>*this</code> 亦不管理对象。等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp">shared_ptr<span class="sy1"><</span>T<span class="sy1">></span><span class="br0">(</span>r<span class="br0">)</span>.<span class="me1">swap</span><span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 从 <code>r</code> 移动赋值 <code>shared_ptr</code> 。赋值后， <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 含有先前 <code>r</code> 状态的副本，而 <code>r</code> 为空，等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp">shared_ptr<span class="sy1"><</span>T<span class="sy1">></span><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>r<span class="br0">)</span><span class="br0">)</span>.<span class="me1">swap</span><span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">3)</span> 转移 <code>r</code> 所管理对象的所有权给 <code>*this</code> 。若 <code>r</code> 不管理对象，则 <code>*this</code> 亦不管理对象。赋值后， <code>*this</code> 含有先前 <code>r</code> 所保有的对象，且 <span class="t-c"><span class="mw-geshi cpp source-cpp">use_count<span class="br0">(</span><span class="br0">)</span><span class="sy1">==</span><span class="nu0">1</span></span></span> ；而 <code>r</code> 为空。等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp">shared_ptr<span class="sy1"><</span>T<span class="sy1">></span><span class="br0">(</span>r<span class="br0">)</span>.<span class="me1">swap</span><span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">4)</span> 转移 <code>r</code> 所管理对象的所有权给 <code>*this</code> 。为将来删除被管理对象，存储关联到 <code>r</code> 的删除器。调用后 <code>r</code> 不管理对象。等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp">shared_ptr<span class="sy1"><</span>T<span class="sy1">></span><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>r<span class="br0">)</span><span class="br0">)</span>.<span class="me1">swap</span><span class="br0">(</span><span class="sy2">*</span>this<span class="br0">)</span></span></span> 。</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<td>r</td>
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<td>-</td>
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<td>要获得所有权或共享所有权的另一智能指针</td>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span></p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p>实现可以满足要求而无需创建临时的 <code>shared_ptr</code> 对象。</p>
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<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
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<div class="t-li1"><span class="t-li">3,4)</span> 可能抛出实现定义的异常。</div>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<td class="mbox-text" style="">本节未完成<br />
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原因：暂无示例</td>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<div><a href="cpp-memory-shared_ptr-reset.html"><span class="t-lines"><span>reset</span></span></a></div>
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<td>替换所管理的对象<br />
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<span class="t-mark">(公开成员函数)</span></td>
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