<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en_US" lang="en_US">
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- qscopedvaluerollback.cpp -->
  <title>Qt 4.8: QScopedValueRollback Class Reference</title>
  <link rel="stylesheet" type="text/css" href="style/style.css" />
  <script src="scripts/jquery.js" type="text/javascript"></script>
  <script src="scripts/functions.js" type="text/javascript"></script>
  <link rel="stylesheet" type="text/css" href="style/superfish.css" />
  <link rel="stylesheet" type="text/css" href="style/narrow.css" />
  <!--[if IE]>
<meta name="MSSmartTagsPreventParsing" content="true">
<meta http-equiv="imagetoolbar" content="no">
<![endif]-->
<!--[if lt IE 7]>
<link rel="stylesheet" type="text/css" href="style/style_ie6.css">
<![endif]-->
<!--[if IE 7]>
<link rel="stylesheet" type="text/css" href="style/style_ie7.css">
<![endif]-->
<!--[if IE 8]>
<link rel="stylesheet" type="text/css" href="style/style_ie8.css">
<![endif]-->

<script src="scripts/superfish.js" type="text/javascript"></script>
<script src="scripts/narrow.js" type="text/javascript"></script>

</head>
<body class="" onload="CheckEmptyAndLoadList();">
 <div class="header" id="qtdocheader">
    <div class="content"> 
    <div id="nav-logo">
      <a href="index.html">Home</a></div>
    <a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
    <div id="narrowsearch"></div>
    <div id="nav-topright">
      <ul>
        <li class="nav-topright-home"><a href="http://qt.digia.com/">Qt HOME</a></li>
        <li class="nav-topright-dev"><a href="http://qt-project.org/">DEV</a></li>
        <li class="nav-topright-doc nav-topright-doc-active"><a href="http://qt-project.org/doc/">
          DOC</a></li>
        <li class="nav-topright-blog"><a href="http://blog.qt.digia.com/">BLOG</a></li>
      </ul>
    </div>
    <div id="shortCut">
      <ul>
        <li class="shortCut-topleft-inactive"><span><a href="index.html">Qt 4.8</a></span></li>
        <li class="shortCut-topleft-active"><a href="http://qt-project.org/doc/">ALL VERSIONS        </a></li>
      </ul>
     </div>
 <ul class="sf-menu" id="narrowmenu"> 
             <li><a href="#">API Lookup</a> 
                 <ul> 
                     <li><a href="classes.html">Class index</a></li> 
           <li><a href="functions.html">Function index</a></li> 
           <li><a href="modules.html">Modules</a></li> 
           <li><a href="namespaces.html">Namespaces</a></li> 
           <li><a href="qtglobal.html">Global Declarations</a></li> 
           <li><a href="qdeclarativeelements.html">QML elements</a></li> 
             </ul> 
             </li> 
             <li><a href="#">Qt Topics</a> 
                 <ul> 
                        <li><a href="qt-basic-concepts.html">Programming with Qt</a></li>  
                        <li><a href="qtquick.html">Device UIs &amp; Qt Quick</a></li>  
                        <li><a href="qt-gui-concepts.html">UI Design with Qt</a></li>  
                        <li><a href="supported-platforms.html">Supported Platforms</a></li>  
                        <li><a href="technology-apis.html">Qt and Key Technologies</a></li>  
                        <li><a href="best-practices.html">How-To's and Best Practices</a></li>  
              </ul> 
                 </li> 
                 <li><a href="#">Examples</a> 
                     <ul> 
                       <li><a href="all-examples.html">Examples</a></li> 
                       <li><a href="tutorials.html">Tutorials</a></li> 
                       <li><a href="demos.html">Demos</a></li> 
                       <li><a href="qdeclarativeexamples.html">QML Examples</a></li> 
                </ul> 
                     </li> 
                 </ul> 
    </div>
  </div>
  <div class="wrapper">
    <div class="hd">
      <span></span>
    </div>
    <div class="bd group">
      <div class="sidebar">
        <div class="searchlabel">
          Search index:</div>
        <div class="search" id="sidebarsearch">
          <form id="qtdocsearch" action="" onsubmit="return false;">
            <fieldset>
              <input type="text" name="searchstring" id="pageType" value="" />
 <div id="resultdialog"> 
 <a href="#" id="resultclose">Close</a> 
 <p id="resultlinks" class="all"><a href="#" id="showallresults">All</a> | <a href="#" id="showapiresults">API</a> | <a href="#" id="showarticleresults">Articles</a> | <a href="#" id="showexampleresults">Examples</a></p> 
 <p id="searchcount" class="all"><span id="resultcount"></span><span id="apicount"></span><span id="articlecount"></span><span id="examplecount"></span>&nbsp;results:</p> 
 <ul id="resultlist" class="all"> 
 </ul> 
 </div> 
            </fieldset>
          </form>
        </div>
        <div class="box first bottombar" id="lookup">
          <h2 title="API Lookup"><span></span>
            API Lookup</h2>
          <div  id="list001" class="list">
          <ul id="ul001" >
              <li class="defaultLink"><a href="classes.html">Class index</a></li>
              <li class="defaultLink"><a href="functions.html">Function index</a></li>
              <li class="defaultLink"><a href="modules.html">Modules</a></li>
              <li class="defaultLink"><a href="namespaces.html">Namespaces</a></li>
              <li class="defaultLink"><a href="qtglobal.html">Global Declarations</a></li>
              <li class="defaultLink"><a href="qdeclarativeelements.html">QML elements</a></li>
            </ul> 
          </div>
        </div>
        <div class="box bottombar" id="topics">
          <h2 title="Qt Topics"><span></span>
            Qt Topics</h2>
          <div id="list002" class="list">
            <ul id="ul002" >
               <li class="defaultLink"><a href="qt-basic-concepts.html">Programming with Qt</a></li> 
               <li class="defaultLink"><a href="qtquick.html">Device UIs &amp; Qt Quick</a></li> 
               <li class="defaultLink"><a href="qt-gui-concepts.html">UI Design with Qt</a></li> 
               <li class="defaultLink"><a href="supported-platforms.html">Supported Platforms</a></li>  
               <li class="defaultLink"><a href="technology-apis.html">Qt and Key Technologies</a></li> 
               <li class="defaultLink"><a href="best-practices.html">How-To's and Best Practices</a></li> 
            </ul>  
          </div>
        </div>
        <div class="box" id="examples">
          <h2 title="Examples"><span></span>
            Examples</h2>
          <div id="list003" class="list">
        <ul id="ul003">
              <li class="defaultLink"><a href="all-examples.html">Examples</a></li>
              <li class="defaultLink"><a href="tutorials.html">Tutorials</a></li>
              <li class="defaultLink"><a href="demos.html">Demos</a></li>
              <li class="defaultLink"><a href="qdeclarativeexamples.html">QML Examples</a></li>
            </ul> 
          </div>
        </div>
      </div>
      <div class="wrap">
        <div class="toolbar">
          <div class="breadcrumb toolblock">
            <ul>
              <li class="first"><a href="index.html">Home</a></li>
              <!--  Breadcrumbs go here -->
<li><a href="modules.html">Modules</a></li>
<li><a href="qtcore.html">QtCore</a></li>
<li>QScopedValueRollback</li>
            </ul>
          </div>
          <div class="toolbuttons toolblock">
            <ul>
              <li id="smallA" class="t_button">A</li>
              <li id="medA" class="t_button active">A</li>
              <li id="bigA" class="t_button">A</li>
              <li id="print" class="t_button"><a href="javascript:this.print();">
                <span>Print</span></a></li>
            </ul>
        </div>
        </div>
        <div class="content mainContent">
<div class="toc">
<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
</ul>
</div>
<h1 class="title">QScopedValueRollback Class Reference</h1>
<!-- $$$QScopedValueRollback-brief -->
<p>The QScopedValueRollback class resets a variable to its previous value on destruction. <a href="#details">More...</a></p>
<!-- @@@QScopedValueRollback -->
<pre class="cpp"> <span class="preprocessor">#include &lt;QScopedValueRollback&gt;</span></pre><p>This class was introduced in Qt 4.8.</p>
<ul>
<li><a href="qscopedvaluerollback-members.html">List of all members, including inherited members</a></li>
</ul>
<a name="public-functions"></a>
<h2>Public Functions</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qscopedvaluerollback.html#QScopedValueRollback">QScopedValueRollback</a></b> ( T &amp; <i>var</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qscopedvaluerollback.html#dtor.QScopedValueRollback">~QScopedValueRollback</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qscopedvaluerollback.html#commit">commit</a></b> ()</td></tr>
</table>
<a name="details"></a>
<!-- $$$QScopedValueRollback-description -->
<div class="descr">
<h2>Detailed Description</h2>
<p>The QScopedValueRollback class resets a variable to its previous value on destruction.</p>
<p>The QScopedAssignment 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>
</div>
<p><b>See also </b><a href="qscopedpointer.html">QScopedPointer</a>.</p>
<!-- @@@QScopedValueRollback -->
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QScopedValueRollback[overload1]$$$QScopedValueRollbackT& -->
<h3 class="fn"><a name="QScopedValueRollback"></a>QScopedValueRollback::<span class="name">QScopedValueRollback</span> ( <span class="type">T</span> &amp; <i>var</i> )</h3>
<p>Stores the previous value of <i>var</i> internally, for revert on destruction.</p>
<!-- @@@QScopedValueRollback -->
<!-- $$$~QScopedValueRollback[overload1]$$$~QScopedValueRollback -->
<h3 class="fn"><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>
<!-- @@@~QScopedValueRollback -->
<!-- $$$commit[overload1]$$$commit -->
<h3 class="fn"><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>
<!-- @@@commit -->
</div>
      </div>
    </div>
    </div> 
    <div class="ft">
      <span></span>
    </div>
  </div> 
  <div class="footer">
    <p>
      <acronym title="Copyright">&copy;</acronym> 2013 Digia Plc and/or its
      subsidiaries. Documentation contributions included herein are the copyrights of
      their respective owners.</p>
    <br />
    <p>
      The documentation provided herein is licensed under the terms of the
      <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation
      License version 1.3</a> as published by the Free Software Foundation.</p>
    <p>
      Documentation sources may be obtained from <a href="http://www.qt-project.org">
      www.qt-project.org</a>.</p>
    <br />
    <p>
      Digia, Qt and their respective logos are trademarks of Digia Plc 
      in Finland and/or other countries worldwide. All other trademarks are property
      of their respective owners. <a title="Privacy Policy"
      href="http://en.gitorious.org/privacy_policy/">Privacy Policy</a></p>
  </div>

  <script src="scripts/functions.js" type="text/javascript"></script>
</body>
</html>
