100 lines
8.3 KiB
HTML
100 lines
8.3 KiB
HTML
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<title>std::move_only_function<R(Args...) cv ref noexcept(noex)>::operator=</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::move_only_function<R(Args...) <i>cv</i> <i>ref</i> noexcept(<i>noex</i>)>::</span>operator=</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-utility.html">utility</a>‎ | <a href="cpp-utility-functional.html">functional</a>‎ | <a href="cpp-utility-functional-move_only_function.html">move only function</a></span></div>
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<div><span class="mw-geshi cpp source-cpp">move_only_function<span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> move_only_function<span class="sy3">&&</span> other <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-cxx23">(C++23 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp">move_only_function<span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> <span class="kw4">const</span> move_only_function<span class="sy3">&</span> <span class="br0">)</span> <span class="sy1">=</span> delete<span class="sy4">;</span></span></div>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-cxx23">(C++23 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp">move_only_function<span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> <a href="cpp-types-nullptr_t.html"><span class="kw102">std::<span class="me2">nullptr_t</span></span></a> <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td>(3)</td>
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<td><span class="t-mark-rev t-since-cxx23">(C++23 起)</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> F <span class="sy1">></span><br />
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move_only_function<span class="sy3">&</span> operator<span class="sy1">=</span><span class="br0">(</span> F<span class="sy3">&&</span> f <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(4)</td>
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<td><span class="t-mark-rev t-since-cxx23">(C++23 起)</span></td>
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<p>指派新目标给 <code>std::move_only_function</code> 或销毁其目标。</p>
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<div class="t-li1"><span class="t-li">1)</span> 通过 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw4">auto</span><span class="br0">(</span>std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>other<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> 移动 <code>other</code> 的目标给 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 或若 <code>other</code> 为空则销毁 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 的目标（若存在）。移动赋值后 <code>other</code> 在有未指定值的合法状态。</div>
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<div class="t-li1"><span class="t-li">2)</span> 复制赋值运算符被删除。 <code>std::move_only_function</code> 不满足<a href="cpp-named_req-CopyAssignable.html"><span style="font-style:italic">可复制赋值</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(CopyAssignable)</span></a> 。</div>
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<div class="t-li1"><span class="t-li">3)</span> 若当前目标存在则销毁它。调用后 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 为空。</div>
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<div class="t-li1"><span class="t-li">4)</span> 如同通过执行 <span class="t-c"><span class="mw-geshi cpp source-cpp">move_only_function<span class="br0">(</span><a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>F<span class="sy1">></span><span class="br0">(</span>f<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 class="sy4">;</span></span></span> 设置 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 的目标为可调用对象 <code>f</code> ，或若 <code>f</code> 为空函数指针、空成员函数指针或空 <code>std::move_only_function</code> 则销毁当前目标。此重载仅若 <code>move_only_function</code> 可从 <code>F</code> 构造才参与重载决议。若选择的构造函数调用非良构或有未定义行为，则程序非良构或有未定义行为。</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>other</td>
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<td>-</td>
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<td>要移动目标的 <code>std::move_only_function</code> 对象</td>
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<td>f</td>
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<td>-</td>
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<td>用以初始化新目标的可调用对象</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>有意不要求移动赋值运算符为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">noexcept</span></span></span> ，以为将来的知分配器的 <code>move_only_function</code> 留出余地。</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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<div><a href="cpp-utility-functional-function-operator=.html"><span class="t-lines"><span>operator=</span></span></a></div>
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<td>为内容赋值<br />
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<span class="t-mark">(<code>std::function<R(Args...)></code> 的公开成员函数)</span></td>
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