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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 >iterator</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right">Qt 5.9.4 Reference Documentation</td>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#public-types">Public Types</a></li>
<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">iterator Class</h1>
<span class="small-subtitle">(<a href="qset-iterator.html">QSet::iterator</a>)<br/></span>
<!-- $$$iterator-brief -->
<p>The <a href="qset-iterator.html">QSet::iterator</a> class provides an STL-style non-const iterator for <a href="qset.html">QSet</a>. <a href="#details">More...</a></p>
<!-- @@@iterator -->
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <<a href="qset.html">QSet</a>></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 4.2</td></tr></table></div><ul>
<li><a href="qset-iterator-members.html">List of all members, including inherited members</a></li>
</ul>
<a name="public-types"></a>
<h2 id="public-types">Public Types</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> typedef </td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#iterator_category-typedef">iterator_category</a></b></td></tr>
</table></div>
<a name="public-functions"></a>
<h2 id="public-functions">Public Functions</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#iterator">iterator</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#iterator-2">iterator</a></b>(const iterator &<i>other</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator-not-eq">operator!=</a></b>(const iterator &<i>other</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator-not-eq-1">operator!=</a></b>(const const_iterator &<i>other</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const T &</td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator-2a">operator*</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> iterator </td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator-2b">operator+</a></b>(int <i>j</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> iterator &</td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator-2b-2b">operator++</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> iterator </td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator-2b-2b-1">operator++</a></b>(<i>int</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> iterator &</td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator-2b-eq">operator+=</a></b>(int <i>j</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> iterator </td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator-">operator-</a></b>(int <i>j</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> iterator &</td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator--">operator--</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> iterator </td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator---1">operator--</a></b>(<i>int</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> iterator &</td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator--eq">operator-=</a></b>(int <i>j</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const T *</td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator--gt">operator-></a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> iterator &</td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator-eq">operator=</a></b>(const iterator &<i>other</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator-eq-eq">operator==</a></b>(const iterator &<i>other</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qset-iterator.html#operator-eq-eq-1">operator==</a></b>(const const_iterator &<i>other</i>) const</td></tr>
</table></div>
<a name="details"></a>
<!-- $$$iterator-description -->
<div class="descr">
<h2 id="details">Detailed Description</h2>
<p>The <a href="qset-iterator.html">QSet::iterator</a> class provides an STL-style non-const iterator for <a href="qset.html">QSet</a>.</p>
<p><a href="qset.html">QSet</a> features both <a href="containers.html#stl-style-iterators">STL-style iterators</a> and <a href="containers.html#java-style-iterators">Java-style iterators</a>. The STL-style iterators are more low-level and more cumbersome to use; on the other hand, they are slightly faster and, for developers who already know STL, have the advantage of familiarity.</p>
<p><a href="qset.html">QSet</a><T>::iterator allows you to iterate over a <a href="qset.html">QSet</a> and to remove items (using <a href="qset.html#erase">QSet::erase</a>()) while you iterate. (<a href="qset.html">QSet</a> doesn't let you <i>modify</i> a value through an iterator, because that would potentially require moving the value in the internal hash table used by <a href="qset.html">QSet</a>.) If you want to iterate over a const <a href="qset.html">QSet</a>, you should use <a href="qset-const-iterator.html">QSet::const_iterator</a>. It is generally good practice to use <a href="qset-const-iterator.html">QSet::const_iterator</a> on a non-const <a href="qset.html">QSet</a> as well, unless you need to change the <a href="qset.html">QSet</a> through the iterator. Const iterators are slightly faster, and can improve code readability.</p>
<p>The default <a href="qset-iterator.html">QSet::iterator</a> constructor creates an uninitialized iterator. You must initialize it using a function like <a href="qset.html#begin">QSet::begin</a>(), <a href="qset.html#end">QSet::end</a>(), or <a href="qset.html#insert">QSet::insert</a>() before you can start iterating. Here's a typical loop that prints all the items stored in a set:</p>
<pre class="cpp">
<span class="type"><a href="qset.html#QSet">QSet</a></span><span class="operator"><</span><span class="type"><a href="qstring.html">QString</a></span><span class="operator">></span> set;
set <span class="operator"><</span><span class="operator"><</span> <span class="string">"January"</span> <span class="operator"><</span><span class="operator"><</span> <span class="string">"February"</span> <span class="operator"><</span><span class="operator"><</span> <span class="operator">.</span><span class="operator">.</span><span class="operator">.</span> <span class="operator"><</span><span class="operator"><</span> <span class="string">"December"</span>;
<span class="type"><a href="qset.html#QSet">QSet</a></span><span class="operator"><</span><span class="type"><a href="qstring.html">QString</a></span><span class="operator">></span><span class="operator">::</span>iterator i;
<span class="keyword">for</span> (i <span class="operator">=</span> set<span class="operator">.</span>begin(); i <span class="operator">!</span><span class="operator">=</span> set<span class="operator">.</span>end(); <span class="operator">+</span><span class="operator">+</span>i)
<a href="qtglobal.html#qDebug">qDebug</a>() <span class="operator"><</span><span class="operator"><</span> <span class="operator">*</span>i;
</pre>
<p>Here's a loop that removes certain items (all those that start with 'J') from a set while iterating:</p>
<pre class="cpp">
<span class="type"><a href="qset.html#QSet">QSet</a></span><span class="operator"><</span><span class="type"><a href="qstring.html">QString</a></span><span class="operator">></span> set;
set <span class="operator"><</span><span class="operator"><</span> <span class="string">"January"</span> <span class="operator"><</span><span class="operator"><</span> <span class="string">"February"</span> <span class="operator"><</span><span class="operator"><</span> <span class="operator">.</span><span class="operator">.</span><span class="operator">.</span> <span class="operator"><</span><span class="operator"><</span> <span class="string">"December"</span>;
<span class="type"><a href="qset.html#QSet">QSet</a></span><span class="operator"><</span><span class="type"><a href="qstring.html">QString</a></span><span class="operator">></span><span class="operator">::</span>iterator i <span class="operator">=</span> set<span class="operator">.</span>begin();
<span class="keyword">while</span> (i <span class="operator">!</span><span class="operator">=</span> set<span class="operator">.</span>end()) {
<span class="keyword">if</span> ((<span class="operator">*</span>i)<span class="operator">.</span>startsWith(<span class="char">'J'</span>)) {
i <span class="operator">=</span> set<span class="operator">.</span>erase(i);
} <span class="keyword">else</span> {
<span class="operator">+</span><span class="operator">+</span>i;
}
}
</pre>
<p>STL-style iterators can be used as arguments to <a href="qtalgorithms.html">generic algorithms</a>. For example, here's how to find an item in the set using the qFind() algorithm:</p>
<pre class="cpp">
<span class="type"><a href="qset.html#QSet">QSet</a></span><span class="operator"><</span><span class="type"><a href="qstring.html">QString</a></span><span class="operator">></span> set;
<span class="operator">.</span><span class="operator">.</span><span class="operator">.</span>
<span class="type"><a href="qset.html#QSet">QSet</a></span><span class="operator"><</span><span class="type"><a href="qstring.html">QString</a></span><span class="operator">></span><span class="operator">::</span>iterator it <span class="operator">=</span> <a href="qtalgorithms-obsolete.html#qFind">qFind</a>(set<span class="operator">.</span>begin()<span class="operator">,</span> set<span class="operator">.</span>end()<span class="operator">,</span> <span class="string">"Jeanette"</span>);
<span class="keyword">if</span> (it <span class="operator">!</span><span class="operator">=</span> set<span class="operator">.</span>end())
cout <span class="operator"><</span><span class="operator"><</span> <span class="string">"Found Jeanette"</span> <span class="operator"><</span><span class="operator"><</span> endl;
</pre>
<p>Multiple iterators can be used on the same set.</p>
<p><b>Warning:</b> Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read <a href="containers.html#implicit-sharing-iterator-problem">Implicit sharing iterator problem</a>.</p>
</div>
<p><b>See also </b><a href="qset-const-iterator.html">QSet::const_iterator</a> and <a href="qmutablesetiterator.html">QMutableSetIterator</a>.</p>
<!-- @@@iterator -->
<div class="types">
<h2>Member Type Documentation</h2>
<!-- $$$iterator_category -->
<h3 class="fn" id="iterator_category-typedef"><a name="iterator_category-typedef"></a>typedef iterator::<span class="name">iterator_category</span></h3>
<p>Synonyms for <i>std::bidirectional_iterator_tag</i> indicating these iterators are bidirectional iterators.</p>
<!-- @@@iterator_category -->
</div>
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$iterator[overload1]$$$iterator -->
<h3 class="fn" id="iterator"><a name="iterator"></a>iterator::<span class="name">iterator</span>()</h3>
<p>Constructs an uninitialized iterator.</p>
<p>Functions like operator*() and operator++() should not be called on an uninitialized iterator. Use operator=() to assign a value to it before using it.</p>
<p><b>See also </b><a href="qset.html#begin">QSet::begin</a>() and <a href="qset.html#end">QSet::end</a>().</p>
<!-- @@@iterator -->
<!-- $$$iterator$$$iteratorconstiterator& -->
<h3 class="fn" id="iterator-2"><a name="iterator-2"></a>iterator::<span class="name">iterator</span>(const <span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> &<i>other</i>)</h3>
<p>Constructs a copy of <i>other</i>.</p>
<!-- @@@iterator -->
<!-- $$$operator!=[overload1]$$$operator!=constiterator& -->
<h3 class="fn" id="operator-not-eq"><a name="operator-not-eq"></a><span class="type">bool</span> iterator::<span class="name">operator!=</span>(const <span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> &<i>other</i>) const</h3>
<p>Returns <code>true</code> if <i>other</i> points to a different item than this iterator; otherwise returns <code>false</code>.</p>
<p><b>See also </b><a href="qset-iterator.html#operator-eq-eq">operator==</a>().</p>
<!-- @@@operator!= -->
<!-- $$$operator!=$$$operator!=constconst_iterator& -->
<h3 class="fn" id="operator-not-eq-1"><a name="operator-not-eq-1"></a><span class="type">bool</span> iterator::<span class="name">operator!=</span>(const <span class="type"><a href="qset-const-iterator.html">const_iterator</a></span> &<i>other</i>) const</h3>
<p>This is an overloaded function.</p>
<!-- @@@operator!= -->
<!-- $$$operator*[overload1]$$$operator* -->
<h3 class="fn" id="operator-2a"><a name="operator-2a"></a>const <span class="type">T</span> &iterator::<span class="name">operator*</span>() const</h3>
<p>Returns a reference to the current item.</p>
<p><b>See also </b><a href="qset-iterator.html#operator--gt">operator-></a>().</p>
<!-- @@@operator* -->
<!-- $$$operator+[overload1]$$$operator+int -->
<h3 class="fn" id="operator-2b"><a name="operator-2b"></a><span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> iterator::<span class="name">operator+</span>(<span class="type">int</span> <i>j</i>) const</h3>
<p>Returns an iterator to the item at <i>j</i> positions forward from this iterator. (If <i>j</i> is negative, the iterator goes backward.)</p>
<p>This operation can be slow for large <i>j</i> values.</p>
<p><b>See also </b><a href="qset-iterator.html#operator-">operator-</a>().</p>
<!-- @@@operator+ -->
<!-- $$$operator++[overload1]$$$operator++ -->
<h3 class="fn" id="operator-2b-2b"><a name="operator-2b-2b"></a><span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> &iterator::<span class="name">operator++</span>()</h3>
<p>The prefix ++ operator (<code>++it</code>) advances the iterator to the next item in the set and returns an iterator to the new current item.</p>
<p>Calling this function on <a href="qset.html#constEnd">QSet::constEnd</a>() leads to undefined results.</p>
<p><b>See also </b><a href="qset-iterator.html#operator--">operator--</a>().</p>
<!-- @@@operator++ -->
<!-- $$$operator++$$$operator++int -->
<h3 class="fn" id="operator-2b-2b-1"><a name="operator-2b-2b-1"></a><span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> iterator::<span class="name">operator++</span>(<i>int</i>)</h3>
<p>This is an overloaded function.</p>
<p>The postfix ++ operator (<code>it++</code>) advances the iterator to the next item in the set and returns an iterator to the previously current item.</p>
<!-- @@@operator++ -->
<!-- $$$operator+=[overload1]$$$operator+=int -->
<h3 class="fn" id="operator-2b-eq"><a name="operator-2b-eq"></a><span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> &iterator::<span class="name">operator+=</span>(<span class="type">int</span> <i>j</i>)</h3>
<p>Advances the iterator by <i>j</i> items. (If <i>j</i> is negative, the iterator goes backward.)</p>
<p>This operation can be slow for large <i>j</i> values.</p>
<p><b>See also </b><a href="qset-iterator.html#operator--eq">operator-=</a>() and <a href="qset-iterator.html#operator-2b">operator+</a>().</p>
<!-- @@@operator+= -->
<!-- $$$operator-[overload1]$$$operator-int -->
<h3 class="fn" id="operator-"><a name="operator-"></a><span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> iterator::<span class="name">operator-</span>(<span class="type">int</span> <i>j</i>) const</h3>
<p>Returns an iterator to the item at <i>j</i> positions backward from this iterator. (If <i>j</i> is negative, the iterator goes forward.)</p>
<p>This operation can be slow for large <i>j</i> values.</p>
<p><b>See also </b><a href="qset-iterator.html#operator-2b">operator+</a>().</p>
<!-- @@@operator- -->
<!-- $$$operator--[overload1]$$$operator-- -->
<h3 class="fn" id="operator--"><a name="operator--"></a><span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> &iterator::<span class="name">operator--</span>()</h3>
<p>The prefix -- operator (<code>--it</code>) makes the preceding item current and returns an iterator to the new current item.</p>
<p>Calling this function on <a href="qset.html#begin">QSet::begin</a>() leads to undefined results.</p>
<p><b>See also </b><a href="qset-iterator.html#operator-2b-2b">operator++</a>().</p>
<!-- @@@operator-- -->
<!-- $$$operator--$$$operator--int -->
<h3 class="fn" id="operator---1"><a name="operator---1"></a><span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> iterator::<span class="name">operator--</span>(<i>int</i>)</h3>
<p>This is an overloaded function.</p>
<p>The postfix -- operator (<code>it--</code>) makes the preceding item current and returns an iterator to the previously current item.</p>
<!-- @@@operator-- -->
<!-- $$$operator-=[overload1]$$$operator-=int -->
<h3 class="fn" id="operator--eq"><a name="operator--eq"></a><span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> &iterator::<span class="name">operator-=</span>(<span class="type">int</span> <i>j</i>)</h3>
<p>Makes the iterator go back by <i>j</i> items. (If <i>j</i> is negative, the iterator goes forward.)</p>
<p>This operation can be slow for large <i>j</i> values.</p>
<p><b>See also </b><a href="qset-iterator.html#operator-2b-eq">operator+=</a>() and <a href="qset-iterator.html#operator-">operator-</a>().</p>
<!-- @@@operator-= -->
<!-- $$$operator->[overload1]$$$operator-> -->
<h3 class="fn" id="operator--gt"><a name="operator--gt"></a>const <span class="type">T</span> *iterator::<span class="name">operator-></span>() const</h3>
<p>Returns a pointer to the current item.</p>
<p><b>See also </b><a href="qset-iterator.html#operator-2a">operator*</a>().</p>
<!-- @@@operator-> -->
<!-- $$$operator=[overload1]$$$operator=constiterator& -->
<h3 class="fn" id="operator-eq"><a name="operator-eq"></a><span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> &iterator::<span class="name">operator=</span>(const <span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> &<i>other</i>)</h3>
<p>Assigns <i>other</i> to this iterator.</p>
<!-- @@@operator= -->
<!-- $$$operator==[overload1]$$$operator==constiterator& -->
<h3 class="fn" id="operator-eq-eq"><a name="operator-eq-eq"></a><span class="type">bool</span> iterator::<span class="name">operator==</span>(const <span class="type"><a href="qset-iterator.html#iterator">iterator</a></span> &<i>other</i>) const</h3>
<p>Returns <code>true</code> if <i>other</i> points to the same item as this iterator; otherwise returns <code>false</code>.</p>
<p><b>See also </b><a href="qset-iterator.html#operator-not-eq">operator!=</a>().</p>
<!-- @@@operator== -->
<!-- $$$operator==$$$operator==constconst_iterator& -->
<h3 class="fn" id="operator-eq-eq-1"><a name="operator-eq-eq-1"></a><span class="type">bool</span> iterator::<span class="name">operator==</span>(const <span class="type"><a href="qset-const-iterator.html">const_iterator</a></span> &<i>other</i>) const</h3>
<p>This is an overloaded function.</p>
<!-- @@@operator== -->
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