72 lines
5.5 KiB
HTML
72 lines
5.5 KiB
HTML
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<title>C++ 具名要求：可移动构造 (MoveConstructible) (C++11 起)</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_named_req_MoveConstructible skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">C++ 具名要求：</span><span style="font-style:italic">可移动构造</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(MoveConstructible)</span> <span class="t-mark-rev t-since-cxx11">(C++11 起)</span></h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-named_req.html">named req</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<p>指定该类型的实例可以从一个<a href="cpp-language-value_category.html">右值</a>实参构造。</p>
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<h3><span class="mw-headline" id=".E8.A6.81.E6.B1.82">要求</span></h3>
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<p>以下情况下，类型 <code>T</code> 满足<span style="font-style:italic">可移动构造</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(MoveConstructible)</span> ：</p>
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<p>给定</p>
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<ul>
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<li><code>T</code> 类型的<a href="cpp-language-value_category.html">右值表达式</a> <code>rv</code></li>
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<li>任意标识符 <code>u</code></li>
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</ul>
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<p>下列表达式必须合法且拥有其指定的效果</p>
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<tr>
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<th>表达式</th>
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<th>后条件</th>
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<tr>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">T u <span class="sy1">=</span> rv<span class="sy4">;</span></span></span></td>
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<td><code>u</code> 的值等于 <code>rv</code> 在初始化前的值。<code>rv</code> 的新值未指明。</td>
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</tr>
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<td><span class="t-c"><span class="mw-geshi cpp source-cpp">T<span class="br0">(</span>rv<span class="br0">)</span></span></span></td>
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<td><code>T(rv)</code> 的值等于 <code>rv</code> 在初始化前的值。<code>rv</code> 的新值未指明。</td>
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</tr>
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</table>
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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>类不必为满足此要求而实现<a href="cpp-language-move_constructor.html">移动构造函数</a>：接收 <code>const T&</code> 实参的<a href="cpp-language-copy_constructor.html">复制构造函数</a>也能绑定右值表达式。</p>
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<p>若<span style="font-style:italic">可移动构造</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(MoveConstructible)</span> 类实现了移动构造函数，则它亦可实现<a href="cpp-utility-move.html">移动语义</a>，以从“构造后 <code>rv</code> 的值未指明”的事实中获利。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-types-is_move_constructible.html"><span class="t-lines"><span>is_move_constructible</span><span>is_trivially_move_constructible</span><span>is_nothrow_move_constructible</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>检查类型是否能从右值引用构造<br />
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<span class="t-mark">(类模板)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-concepts-move_constructible.html"><span class="t-lines"><span>move_constructible</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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</div>
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</td>
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<td>指定能移动构造一个类型的对象<br />
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<span class="t-mark">(概念)</span></td>
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</tr>
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