81 lines
4.9 KiB
HTML
81 lines
4.9 KiB
HTML
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<title>std::promise<R>::promise</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_thread_promise_promise 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::promise<R>::</span>promise</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-thread.html">thread</a>‎ | <a href="cpp-thread-promise.html">promise</a></span></div>
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<div><span class="mw-geshi cpp source-cpp">promise<span class="br0">(</span><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-cxx11">(C++11 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> Alloc <span class="sy1">></span><br />
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promise<span class="br0">(</span> <a href="cpp-memory-allocator_arg_t.html"><span class="kw702">std::<span class="me2">allocator_arg_t</span></span></a>, <span class="kw4">const</span> Alloc<span class="sy3">&</span> alloc <span class="br0">)</span><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-cxx11">(C++11 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp">promise<span class="br0">(</span> promise<span class="sy3">&&</span> other <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-cxx11">(C++11 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp">promise<span class="br0">(</span> <span class="kw4">const</span> promise<span class="sy3">&</span> other <span class="br0">)</span> <span class="sy1">=</span> delete<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-cxx11">(C++11 起)</span></td>
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<p>构造 <code>std::promise</code> 对象。</p>
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<div class="t-li1"><span class="t-li">1)</span> 默认构造函数，构造一个共享状态为空的 <code>std::promise</code> ；</div>
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<div class="t-li1"><span class="t-li">2)</span> 构造一个共享状态为空的 <code>std::promise</code>，由 <code>alloc</code> 分配共享状态， <code>Alloc</code> 必须满足<a href="cpp-named_req-Allocator.html"><span style="font-style:italic">分配器</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(Allocator)</span></a> 的要求；</div>
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<div class="t-li1"><span class="t-li">3)</span> 移动构造函数，用原属 <code>other</code> 的共享状态构造新的 <code>std::promise</code> 对象，使用移动语义。构造完毕后， <code>other</code> 无共享状态；</div>
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<div class="t-li1"><span class="t-li">4)</span> <code>std::promise</code> 不可复制。</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>alloc</td>
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<td>-</td>
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<td>分配器，用于分配共享状态；</td>
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<td>other</td>
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<td>-</td>
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<td>另一 <code>std::promise</code> 对象，作为获得共享状态的来源。</td>
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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">1-2)</span> 可能抛出实现定义的异常。</div>
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