79 lines
5.2 KiB
HTML
79 lines
5.2 KiB
HTML
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<title>std::unique_ptr<T,Deleter>::operator bool</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_memory_unique_ptr_operator_bool 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::unique_ptr<T,Deleter>::</span>operator bool</h1>
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<div id="bodyContent">
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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-unique_ptr.html">unique ptr</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">explicit</span> operator <span class="kw4">bool</span><span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
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<td></td>
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<p>检查 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 是否占有对象，即是否有 <span class="t-c"><span class="mw-geshi cpp source-cpp">get<span class="br0">(</span><span class="br0">)</span> <span class="sy3">!</span><span class="sy1">=</span> nullptr</span></span> 。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<p>（无）</p>
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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>若 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 占有对象则为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> ，否则为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <iostream></span>
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<span class="co2">#include <memory></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="cpp-memory-unique_ptr.html"><span class="kw733">std::<span class="me2">unique_ptr</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> ptr<span class="br0">(</span>new <span class="kw4">int</span><span class="br0">(</span><span class="nu0">42</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>ptr<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">"before reset, ptr is: "</span> <span class="sy1"><<</span> <span class="sy2">*</span>ptr <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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ptr.<span class="me1">reset</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>ptr<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">"after reset, ptr is: "</span> <span class="sy1"><<</span> <span class="sy2">*</span>ptr <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">before reset, ptr is: 42</pre></div>
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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-unique_ptr-get.html"><span class="t-lines"><span>get</span></span></a></div>
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</td>
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<td>返回指向被管理对象的指针<br />
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<span class="t-mark">(公开成员函数)</span></td>
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