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<td >Qt 5.9</td><td ><a href="qtcore-index.html">Qt Core</a></td><td ><a href="qtcore-module.html">C++ Classes</a></td><td >QScopedValueRollback</td></tr></table><table class="buildversion"><tr>
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<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
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<h1 class="title">QScopedValueRollback Class</h1>
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<p>The <a href="qscopedvaluerollback.html">QScopedValueRollback</a> class resets a variable to its previous value on destruction. <a href="#details">More...</a></p>
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<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QScopedValueRollback></span>
</td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += core</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Since:</td><td class="memItemRight bottomAlign"> Qt 4.8</td></tr></table></div><ul>
<li><a href="qscopedvaluerollback-members.html">List of all members, including inherited members</a></li>
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<h2 id="public-functions">Public Functions</h2>
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<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qscopedvaluerollback.html#QScopedValueRollback">QScopedValueRollback</a></b>(T &<i>var</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qscopedvaluerollback.html#QScopedValueRollback-1">QScopedValueRollback</a></b>(T &<i>var</i>, T <i>value</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qscopedvaluerollback.html#dtor.QScopedValueRollback">~QScopedValueRollback</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qscopedvaluerollback.html#commit">commit</a></b>()</td></tr>
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<h2 id="details">Detailed Description</h2>
<p>The <a href="qscopedvaluerollback.html">QScopedValueRollback</a> class resets a variable to its previous value on destruction.</p>
<p>The <a href="qscopedvaluerollback.html">QScopedValueRollback</a> class can be used to revert state when an exception is thrown without needing to write try-catch blocks.</p>
<p>It can also be used to manage variables that are temporarily set, such as reentrancy guards. By using this class, the variable will be reset whether the function is exited normally, exited early by a return statement, or exited by an exception.</p>
<p>The template can only be instantiated with a type that supports assignment.</p>
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<p><b>See also </b><a href="qscopedpointer.html">QScopedPointer</a>.</p>
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<h2>Member Function Documentation</h2>
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<h3 class="fn" id="QScopedValueRollback"><a name="QScopedValueRollback"></a>QScopedValueRollback::<span class="name">QScopedValueRollback</span>(<span class="type">T</span> &<i>var</i>)</h3>
<p>Stores the previous value of <i>var</i> internally, for revert on destruction.</p>
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<h3 class="fn" id="QScopedValueRollback-1"><a name="QScopedValueRollback-1"></a>QScopedValueRollback::<span class="name">QScopedValueRollback</span>(<span class="type">T</span> &<i>var</i>, <span class="type">T</span> <i>value</i>)</h3>
<p>Assigns <i>value</i> to var and stores the previous value of <i>var</i> internally, for revert on destruction.</p>
<p>This function was introduced in Qt 5.4.</p>
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<h3 class="fn" id="dtor.QScopedValueRollback"><a name="dtor.QScopedValueRollback"></a>QScopedValueRollback::<span class="name">~QScopedValueRollback</span>()</h3>
<p>Assigns the previous value to the managed variable. This is the value at construction time, or at the last call to <a href="qscopedvaluerollback.html#commit">commit</a>()</p>
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<h3 class="fn" id="commit"><a name="commit"></a><span class="type">void</span> QScopedValueRollback::<span class="name">commit</span>()</h3>
<p>Updates the previous value of the managed variable to its current value.</p>
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