<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- qiterator.qdoc -->
<title>QMutableListIterator Class | Qt Core 5.9</title>
<link rel="stylesheet" type="text/css" href="style/offline-simple.css" />
<script type="text/javascript">
document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css");
// loading style sheet breaks anchors that were jumped to before
// so force jumping to anchor again
setTimeout(function() {
var anchor = location.hash;
// need to jump to different anchor first (e.g. none)
location.hash = "#";
setTimeout(function() {
location.hash = anchor;
}, 0);
}, 0);
</script>
</head>
<body>
<div class="header" id="qtdocheader">
<div class="main">
<div class="main-rounded">
<div class="navigationbar">
<table><tr>
<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 >QMutableListIterator</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right">Qt 5.9.4 Reference Documentation</td>
</tr></table>
</div>
</div>
<div class="content">
<div class="line">
<div class="content mainContent">
<div class="sidebar">
<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>
<div class="sidebar-content" id="sidebar-content"></div></div>
<h1 class="title">QMutableListIterator Class</h1>
<!-- $$$QMutableListIterator-brief -->
<p>The <a href="qmutablelistiterator.html">QMutableListIterator</a> class provides a Java-style non-const iterator for <a href="qlist.html">QList</a> and <a href="qqueue.html">QQueue</a>. <a href="#details">More...</a></p>
<!-- @@@QMutableListIterator -->
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QMutableListIterator></span>
</td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += core</td></tr></table></div><ul>
<li><a href="qmutablelistiterator-members.html">List of all members, including inherited members</a></li>
</ul>
<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="qmutablelistiterator.html#QMutableListIterator">QMutableListIterator</a></b>(QList<T> &<i>list</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#findNext">findNext</a></b>(const T &<i>value</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#findPrevious">findPrevious</a></b>(const T &<i>value</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#hasNext">hasNext</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#hasPrevious">hasPrevious</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#insert">insert</a></b>(const T &<i>value</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T &</td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#next">next</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T &</td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#peekNext">peekNext</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T &</td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#peekPrevious">peekPrevious</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T &</td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#previous">previous</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#remove">remove</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#setValue">setValue</a></b>(const T &<i>value</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#toBack">toBack</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#toFront">toFront</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const T &</td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#value">value</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> T &</td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#value-1">value</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QMutableListIterator &</td><td class="memItemRight bottomAlign"><b><a href="qmutablelistiterator.html#operator-eq">operator=</a></b>(QList<T> &<i>list</i>)</td></tr>
</table></div>
<a name="details"></a>
<!-- $$$QMutableListIterator-description -->
<div class="descr">
<h2 id="details">Detailed Description</h2>
<p>The <a href="qmutablelistiterator.html">QMutableListIterator</a> class provides a Java-style non-const iterator for <a href="qlist.html">QList</a> and <a href="qqueue.html">QQueue</a>.</p>
<p><a href="qlist.html">QList</a> has both <a href="containers.html#java-style-iterators">Java-style iterators</a> and <a href="containers.html#stl-style-iterators">STL-style iterators</a>. The Java-style iterators are more high-level and easier to use than the STL-style iterators; on the other hand, they are slightly less efficient.</p>
<p>An alternative to using iterators is to use index positions. Most <a href="qlist.html">QList</a> member functions take an index as their first parameter, making it possible to access, insert, and remove items without using iterators.</p>
<p><a href="qmutablelistiterator.html">QMutableListIterator</a><T> allows you to iterate over a <a href="qlist.html">QList</a><T> (or a <a href="qqueue.html">QQueue</a><T>) and modify the list. If you don't want to modify the list (or have a const <a href="qlist.html">QList</a>), use the slightly faster <a href="qlistiterator.html">QListIterator</a><T> instead.</p>
<p>The <a href="qmutablelistiterator.html">QMutableListIterator</a> constructor takes a <a href="qlist.html">QList</a> as argument. After construction, the iterator is located at the very beginning of the list (before the first item). Here's how to iterate over all the elements sequentially:</p>
<pre class="cpp">
<span class="type"><a href="qlist.html">QList</a></span><span class="operator"><</span><span class="type">float</span><span class="operator">></span> list;
<span class="operator">.</span><span class="operator">.</span><span class="operator">.</span>
<span class="type"><a href="qmutablelistiterator.html#QMutableListIterator">QMutableListIterator</a></span><span class="operator"><</span><span class="type">float</span><span class="operator">></span> i(list);
<span class="keyword">while</span> (i<span class="operator">.</span>hasNext())
<a href="qtglobal.html#qDebug">qDebug</a>() <span class="operator"><</span><span class="operator"><</span> i<span class="operator">.</span>next();
</pre>
<p>The <a href="qmutablelistiterator.html#next">next</a>() function returns the next item in the list and advances the iterator. Unlike STL-style iterators, Java-style iterators point <i>between</i> items rather than directly <i>at</i> items. The first call to <a href="qmutablelistiterator.html#next">next</a>() advances the iterator to the position between the first and second item, and returns the first item; the second call to <a href="qmutablelistiterator.html#next">next</a>() advances the iterator to the position between the second and third item, returning the second item; and so on.</p>
<p class="centerAlign"><img src="images/javaiterators1.png" alt="" /></p><p>Here's how to iterate over the elements in reverse order:</p>
<pre class="cpp">
<span class="type"><a href="qmutablelistiterator.html#QMutableListIterator">QMutableListIterator</a></span><span class="operator"><</span><span class="type">float</span><span class="operator">></span> i(list);
i<span class="operator">.</span>toBack();
<span class="keyword">while</span> (i<span class="operator">.</span>hasPrevious())
<a href="qtglobal.html#qDebug">qDebug</a>() <span class="operator"><</span><span class="operator"><</span> i<span class="operator">.</span>previous();
</pre>
<p>If you want to find all occurrences of a particular value, use <a href="qmutablelistiterator.html#findNext">findNext</a>() or <a href="qmutablelistiterator.html#findPrevious">findPrevious</a>() in a loop.</p>
<p>If you want to remove items as you iterate over the list, use <a href="qmutablelistiterator.html#remove">remove</a>(). If you want to modify the value of an item, use <a href="qmutablelistiterator.html#setValue">setValue</a>(). If you want to insert a new item in the list, use <a href="qmutablelistiterator.html#insert">insert</a>().</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qmutablelistiterator.html#QMutableListIterator">QMutableListIterator</a></span><span class="operator"><</span><span class="type">int</span><span class="operator">></span> i(list);
<span class="keyword">while</span> (i<span class="operator">.</span>hasNext()) {
<span class="type">int</span> val <span class="operator">=</span> i<span class="operator">.</span>next();
<span class="keyword">if</span> (val <span class="operator"><</span> <span class="number">0</span>) {
i<span class="operator">.</span>setValue(<span class="operator">-</span>val);
} <span class="keyword">else</span> <span class="keyword">if</span> (val <span class="operator">=</span><span class="operator">=</span> <span class="number">0</span>) {
i<span class="operator">.</span>remove();
}
}
</pre>
<p>The example traverses a list, replacing negative numbers with their absolute values, and eliminating zeroes.</p>
<p>Only one mutable iterator can be active on a given list at any time. Furthermore, no changes should be done directly to the list while the iterator is active (as opposed to through the iterator), since this could invalidate the iterator and lead to undefined behavior.</p>
</div>
<p><b>See also </b><a href="qlistiterator.html">QListIterator</a> and <a href="qlist-iterator.html">QList::iterator</a>.</p>
<!-- @@@QMutableListIterator -->
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QMutableListIterator[overload1]$$$QMutableListIteratorQList<T>& -->
<h3 class="fn" id="QMutableListIterator"><a name="QMutableListIterator"></a>QMutableListIterator::<span class="name">QMutableListIterator</span>(<span class="type"><a href="qlist.html">QList</a></span><<span class="type">T</span>> &<i>list</i>)</h3>
<p>Constructs an iterator for traversing <i>list</i>. The iterator is set to be at the front of the list (before the first item).</p>
<p><b>See also </b><a href="qmutablelistiterator.html#operator-eq">operator=</a>().</p>
<!-- @@@QMutableListIterator -->
<!-- $$$findNext[overload1]$$$findNextconstT& -->
<h3 class="fn" id="findNext"><a name="findNext"></a><span class="type">bool</span> QMutableListIterator::<span class="name">findNext</span>(const <span class="type">T</span> &<i>value</i>)</h3>
<p>Searches for <i>value</i> starting from the current iterator position forward. Returns <code>true</code> if <i>value</i> is found; otherwise returns <code>false</code>.</p>
<p>After the call, if <i>value</i> was found, the iterator is positioned just after the matching item; otherwise, the iterator is positioned at the back of the container.</p>
<p><b>See also </b><a href="qmutablelistiterator.html#findPrevious">findPrevious</a>().</p>
<!-- @@@findNext -->
<!-- $$$findPrevious[overload1]$$$findPreviousconstT& -->
<h3 class="fn" id="findPrevious"><a name="findPrevious"></a><span class="type">bool</span> QMutableListIterator::<span class="name">findPrevious</span>(const <span class="type">T</span> &<i>value</i>)</h3>
<p>Searches for <i>value</i> starting from the current iterator position backward. Returns <code>true</code> if <i>value</i> is found; otherwise returns false.</p>
<p>After the call, if <i>value</i> was found, the iterator is positioned just before the matching item; otherwise, the iterator is positioned at the front of the container.</p>
<p><b>See also </b><a href="qmutablelistiterator.html#findNext">findNext</a>().</p>
<!-- @@@findPrevious -->
<!-- $$$hasNext[overload1]$$$hasNext -->
<h3 class="fn" id="hasNext"><a name="hasNext"></a><span class="type">bool</span> QMutableListIterator::<span class="name">hasNext</span>() const</h3>
<p>Returns <code>true</code> if there is at least one item ahead of the iterator, i.e. the iterator is <i>not</i> at the back of the container; otherwise returns <code>false</code>.</p>
<p><b>See also </b><a href="qmutablelistiterator.html#hasPrevious">hasPrevious</a>() and <a href="qmutablelistiterator.html#next">next</a>().</p>
<!-- @@@hasNext -->
<!-- $$$hasPrevious[overload1]$$$hasPrevious -->
<h3 class="fn" id="hasPrevious"><a name="hasPrevious"></a><span class="type">bool</span> QMutableListIterator::<span class="name">hasPrevious</span>() const</h3>
<p>Returns <code>true</code> if there is at least one item behind the iterator, i.e. the iterator is <i>not</i> at the front of the container; otherwise returns <code>false</code>.</p>
<p><b>See also </b><a href="qmutablelistiterator.html#hasNext">hasNext</a>() and <a href="qmutablelistiterator.html#previous">previous</a>().</p>
<!-- @@@hasPrevious -->
<!-- $$$insert[overload1]$$$insertconstT& -->
<h3 class="fn" id="insert"><a name="insert"></a><span class="type">void</span> QMutableListIterator::<span class="name">insert</span>(const <span class="type">T</span> &<i>value</i>)</h3>
<p>Inserts <i>value</i> at the current iterator position. After the call, the iterator is located just after the inserted item.</p>
<p><b>See also </b><a href="qmutablelistiterator.html#remove">remove</a>() and <a href="qmutablelistiterator.html#setValue">setValue</a>().</p>
<!-- @@@insert -->
<!-- $$$next[overload1]$$$next -->
<h3 class="fn" id="next"><a name="next"></a><span class="type">T</span> &QMutableListIterator::<span class="name">next</span>()</h3>
<p>Returns a reference to the next item, and advances the iterator by one position.</p>
<p>Calling this function on an iterator located at the back of the container leads to undefined results.</p>
<p><b>See also </b><a href="qmutablelistiterator.html#hasNext">hasNext</a>(), <a href="qmutablelistiterator.html#peekNext">peekNext</a>(), and <a href="qmutablelistiterator.html#previous">previous</a>().</p>
<!-- @@@next -->
<!-- $$$peekNext[overload1]$$$peekNext -->
<h3 class="fn" id="peekNext"><a name="peekNext"></a><span class="type">T</span> &QMutableListIterator::<span class="name">peekNext</span>() const</h3>
<p>Returns a reference to the next item, without moving the iterator.</p>
<p>Calling this function on an iterator located at the back of the container leads to undefined results.</p>
<p><b>See also </b><a href="qmutablelistiterator.html#hasNext">hasNext</a>(), <a href="qmutablelistiterator.html#next">next</a>(), and <a href="qmutablelistiterator.html#peekPrevious">peekPrevious</a>().</p>
<!-- @@@peekNext -->
<!-- $$$peekPrevious[overload1]$$$peekPrevious -->
<h3 class="fn" id="peekPrevious"><a name="peekPrevious"></a><span class="type">T</span> &QMutableListIterator::<span class="name">peekPrevious</span>() const</h3>
<p>Returns a reference to the previous item, without moving the iterator.</p>
<p>Calling this function on an iterator located at the front of the container leads to undefined results.</p>
<p><b>See also </b><a href="qmutablelistiterator.html#hasPrevious">hasPrevious</a>(), <a href="qmutablelistiterator.html#previous">previous</a>(), and <a href="qmutablelistiterator.html#peekNext">peekNext</a>().</p>
<!-- @@@peekPrevious -->
<!-- $$$previous[overload1]$$$previous -->
<h3 class="fn" id="previous"><a name="previous"></a><span class="type">T</span> &QMutableListIterator::<span class="name">previous</span>()</h3>
<p>Returns a reference to the previous item and moves the iterator back by one position.</p>
<p>Calling this function on an iterator located at the front of the container leads to undefined results.</p>
<p><b>See also </b><a href="qmutablelistiterator.html#hasPrevious">hasPrevious</a>(), <a href="qmutablelistiterator.html#peekPrevious">peekPrevious</a>(), and <a href="qmutablelistiterator.html#next">next</a>().</p>
<!-- @@@previous -->
<!-- $$$remove[overload1]$$$remove -->
<h3 class="fn" id="remove"><a name="remove"></a><span class="type">void</span> QMutableListIterator::<span class="name">remove</span>()</h3>
<p>Removes the last item that was jumped over using one of the traversal functions (<a href="qmutablelistiterator.html#next">next</a>(), <a href="qmutablelistiterator.html#previous">previous</a>(), <a href="qmutablelistiterator.html#findNext">findNext</a>(), <a href="qmutablelistiterator.html#findPrevious">findPrevious</a>()).</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qmutablelistiterator.html#QMutableListIterator">QMutableListIterator</a></span><span class="operator"><</span><span class="type">int</span><span class="operator">></span> i(list);
<span class="keyword">while</span> (i<span class="operator">.</span>hasNext()) {
<span class="type">int</span> val <span class="operator">=</span> i<span class="operator">.</span>next();
<span class="keyword">if</span> (val <span class="operator"><</span> <span class="operator">-</span><span class="number">32768</span> <span class="operator">|</span><span class="operator">|</span> val <span class="operator">></span> <span class="number">32767</span>)
i<span class="operator">.</span>remove();
}
</pre>
<p><b>See also </b><a href="qmutablelistiterator.html#insert">insert</a>() and <a href="qmutablelistiterator.html#setValue">setValue</a>().</p>
<!-- @@@remove -->
<!-- $$$setValue[overload1]$$$setValueconstT& -->
<h3 class="fn" id="setValue"><a name="setValue"></a><span class="type">void</span> QMutableListIterator::<span class="name">setValue</span>(const <span class="type">T</span> &<i>value</i>) const</h3>
<p>Replaces the value of the last item that was jumped over using one of the traversal functions with <i>value</i>.</p>
<p>The traversal functions are <a href="qmutablelistiterator.html#next">next</a>(), <a href="qmutablelistiterator.html#previous">previous</a>(), <a href="qmutablelistiterator.html#findNext">findNext</a>(), and <a href="qmutablelistiterator.html#findPrevious">findPrevious</a>().</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qmutablelistiterator.html#QMutableListIterator">QMutableListIterator</a></span><span class="operator"><</span><span class="type">double</span><span class="operator">></span> i(list);
<span class="keyword">while</span> (i<span class="operator">.</span>hasNext()) {
<span class="type">double</span> val <span class="operator">=</span> i<span class="operator">.</span>next();
i<span class="operator">.</span>setValue(std<span class="operator">::</span>sqrt(val));
}
</pre>
<p><b>See also </b><a href="qmutablelistiterator.html#value">value</a>(), <a href="qmutablelistiterator.html#remove">remove</a>(), and <a href="qmutablelistiterator.html#insert">insert</a>().</p>
<!-- @@@setValue -->
<!-- $$$toBack[overload1]$$$toBack -->
<h3 class="fn" id="toBack"><a name="toBack"></a><span class="type">void</span> QMutableListIterator::<span class="name">toBack</span>()</h3>
<p>Moves the iterator to the back of the container (after the last item).</p>
<p><b>See also </b><a href="qmutablelistiterator.html#toFront">toFront</a>() and <a href="qmutablelistiterator.html#previous">previous</a>().</p>
<!-- @@@toBack -->
<!-- $$$toFront[overload1]$$$toFront -->
<h3 class="fn" id="toFront"><a name="toFront"></a><span class="type">void</span> QMutableListIterator::<span class="name">toFront</span>()</h3>
<p>Moves the iterator to the front of the container (before the first item).</p>
<p><b>See also </b><a href="qmutablelistiterator.html#toBack">toBack</a>() and <a href="qmutablelistiterator.html#next">next</a>().</p>
<!-- @@@toFront -->
<!-- $$$value[overload1]$$$value -->
<h3 class="fn" id="value"><a name="value"></a>const <span class="type">T</span> &QMutableListIterator::<span class="name">value</span>() const</h3>
<p>Returns the value of the last item that was jumped over using one of the traversal functions (<a href="qmutablelistiterator.html#next">next</a>(), <a href="qmutablelistiterator.html#previous">previous</a>(), <a href="qmutablelistiterator.html#findNext">findNext</a>(), <a href="qmutablelistiterator.html#findPrevious">findPrevious</a>()).</p>
<p>After a call to <a href="qmutablelistiterator.html#next">next</a>() or <a href="qmutablelistiterator.html#findNext">findNext</a>(), value() is equivalent to <a href="qmutablelistiterator.html#peekPrevious">peekPrevious</a>(). After a call to <a href="qmutablelistiterator.html#previous">previous</a>() or <a href="qmutablelistiterator.html#findPrevious">findPrevious</a>(), value() is equivalent to <a href="qmutablelistiterator.html#peekNext">peekNext</a>().</p>
<p><b>See also </b><a href="qmutablelistiterator.html#setValue">setValue</a>().</p>
<!-- @@@value -->
<!-- $$$value$$$value -->
<h3 class="fn" id="value-1"><a name="value-1"></a><span class="type">T</span> &QMutableListIterator::<span class="name">value</span>()</h3>
<p>This is an overloaded function.</p>
<p>Returns a non-const reference to the value of the last item that was jumped over using one of the traversal functions.</p>
<!-- @@@value -->
<!-- $$$operator=[overload1]$$$operator=QList<T>& -->
<h3 class="fn" id="operator-eq"><a name="operator-eq"></a><span class="type"><a href="qmutablelistiterator.html#QMutableListIterator">QMutableListIterator</a></span> &QMutableListIterator::<span class="name">operator=</span>(<span class="type"><a href="qlist.html">QList</a></span><<span class="type">T</span>> &<i>list</i>)</h3>
<p>Makes the iterator operate on <i>list</i>. The iterator is set to be at the front of the list (before the first item).</p>
<p><b>See also </b><a href="qmutablelistiterator.html#toFront">toFront</a>() and <a href="qmutablelistiterator.html#toBack">toBack</a>().</p>
<!-- @@@operator= -->
</div>
</div>
</div>
</div>
</div>
</div>
<div class="footer">
<p>
<acronym title="Copyright">©</acronym> 2017 The Qt Company Ltd.
Documentation contributions included herein are the copyrights of
their respective owners.<br> 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.<br> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property
of their respective owners. </p>
</div>
</body>
</html>
distrib
>
Mageia
>
6
>
armv5tl
>
media
>
core-updates
>
by-pkgid
>
768f7d9f703884aa2562bf0a651086df
>
files
>
541
