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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 >QMultiHash</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-functions">Public Functions</a></li>
<li class="level1"><a href="#related-non-members">Related Non-Members</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
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<h1 class="title">QMultiHash Class</h1>
<!-- $$$QMultiHash-brief -->
<p>The <a href="qmultihash.html">QMultiHash</a> class is a convenience <a href="qhash.html#qhash">QHash</a> subclass that provides multi-valued hashes. <a href="#details">More...</a></p>
<!-- @@@QMultiHash -->
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QMultiHash></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"> Inherits:</td><td class="memItemRight bottomAlign"> <a href="qhash.html">QHash</a></td></tr></table></div><ul>
<li><a href="qmultihash-members.html">List of all members, including inherited members</a></li>
</ul>
<p><b>Note:</b> All functions in this class are reentrant.</p>
<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="qmultihash.html#QMultiHash">QMultiHash</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#QMultiHash-1">QMultiHash</a></b>(std::initializer_list<std::pair<Key, T> > <i>list</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#QMultiHash-2">QMultiHash</a></b>(const QHash<Key, T> &<i>other</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#QMultiHash-3">QMultiHash</a></b>(QHash<Key, T> &&<i>other</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QHash<Key, T>::const_iterator </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#constFind">constFind</a></b>(const Key &<i>key</i>, const T &<i>value</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#contains">contains</a></b>(const Key &<i>key</i>, const T &<i>value</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#count">count</a></b>(const Key &<i>key</i>, const T &<i>value</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QHash<Key, T>::iterator </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#find">find</a></b>(const Key &<i>key</i>, const T &<i>value</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QHash<Key, T>::const_iterator </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#find-1">find</a></b>(const Key &<i>key</i>, const T &<i>value</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QHash<Key, T>::iterator </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#insert">insert</a></b>(const Key &<i>key</i>, const T &<i>value</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#remove">remove</a></b>(const Key &<i>key</i>, const T &<i>value</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QHash<Key, T>::iterator </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#replace">replace</a></b>(const Key &<i>key</i>, const T &<i>value</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#swap">swap</a></b>(QMultiHash &<i>other</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QMultiHash </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#operator-2b">operator+</a></b>(const QMultiHash &<i>other</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QMultiHash &</td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#operator-2b-eq">operator+=</a></b>(const QMultiHash &<i>other</i>)</td></tr>
</table></div>
<ul>
<li class="fn">48 public functions inherited from <a href="qhash.html#public-functions">QHash</a></li>
</ul>
<a name="related-non-members"></a>
<h2 id="related-non-members">Related Non-Members</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> uint </td><td class="memItemRight bottomAlign"><b><a href="qmultihash.html#qHash">qHash</a></b>(const QMultiHash<Key, T> &<i>key</i>, uint <i>seed</i> = 0)</td></tr>
</table></div>
<a name="details"></a>
<!-- $$$QMultiHash-description -->
<div class="descr">
<h2 id="details">Detailed Description</h2>
<p>The <a href="qmultihash.html">QMultiHash</a> class is a convenience <a href="qhash.html#qhash">QHash</a> subclass that provides multi-valued hashes.</p>
<p><a href="qmultihash.html">QMultiHash</a><Key, T> is one of Qt's generic <a href="containers.html">container classes</a>. It inherits <a href="qhash.html#qhash">QHash</a> and extends it with a few convenience functions that make it more suitable than <a href="qhash.html#qhash">QHash</a> for storing multi-valued hashes. A multi-valued hash is a hash that allows multiple values with the same key; <a href="qhash.html#qhash">QHash</a> normally doesn't allow that, unless you call <a href="qhash.html#insertMulti">QHash::insertMulti</a>().</p>
<p>Because <a href="qmultihash.html">QMultiHash</a> inherits <a href="qhash.html#qhash">QHash</a>, all of <a href="qhash.html#qhash">QHash</a>'s functionality also applies to <a href="qmultihash.html">QMultiHash</a>. For example, you can use <a href="qhash.html#isEmpty">isEmpty</a>() to test whether the hash is empty, and you can traverse a <a href="qmultihash.html">QMultiHash</a> using <a href="qhash.html#qhash">QHash</a>'s iterator classes (for example, <a href="qhashiterator.html">QHashIterator</a>). But in addition, it provides an <a href="qmultihash.html#insert">insert</a>() function that corresponds to <a href="qhash.html#insertMulti">QHash::insertMulti</a>(), and a <a href="qmultihash.html#replace">replace</a>() function that corresponds to <a href="qhash.html#insert">QHash::insert</a>(). It also provides convenient operator+() and operator+=().</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qmultihash.html#QMultiHash">QMultiHash</a></span><span class="operator"><</span><span class="type"><a href="qstring.html">QString</a></span><span class="operator">,</span> <span class="type">int</span><span class="operator">></span> hash1<span class="operator">,</span> hash2<span class="operator">,</span> hash3;
hash1<span class="operator">.</span>insert(<span class="string">"plenty"</span><span class="operator">,</span> <span class="number">100</span>);
hash1<span class="operator">.</span>insert(<span class="string">"plenty"</span><span class="operator">,</span> <span class="number">2000</span>);
<span class="comment">// hash1.size() == 2</span>
hash2<span class="operator">.</span>insert(<span class="string">"plenty"</span><span class="operator">,</span> <span class="number">5000</span>);
<span class="comment">// hash2.size() == 1</span>
hash3 <span class="operator">=</span> hash1 <span class="operator">+</span> hash2;
<span class="comment">// hash3.size() == 3</span>
</pre>
<p>Unlike <a href="qhash.html#qhash">QHash</a>, <a href="qmultihash.html">QMultiHash</a> provides no operator[]. Use <a href="qhash.html#value">value</a>() or <a href="qmultihash.html#replace">replace</a>() if you want to access the most recently inserted item with a certain key.</p>
<p>If you want to retrieve all the values for a single key, you can use values(const Key &key), which returns a <a href="qlist.html">QList</a><T>:</p>
<pre class="cpp">
<span class="type"><a href="qlist.html">QList</a></span><span class="operator"><</span><span class="type">int</span><span class="operator">></span> values <span class="operator">=</span> hash<span class="operator">.</span>values(<span class="string">"plenty"</span>);
<span class="keyword">for</span> (<span class="type">int</span> i <span class="operator">=</span> <span class="number">0</span>; i <span class="operator"><</span> values<span class="operator">.</span>size(); <span class="operator">+</span><span class="operator">+</span>i)
cout <span class="operator"><</span><span class="operator"><</span> values<span class="operator">.</span>at(i) <span class="operator"><</span><span class="operator"><</span> endl;
</pre>
<p>The items that share the same key are available from most recently to least recently inserted.</p>
<p>A more efficient approach is to call <a href="qmultihash.html#find">find</a>() to get the STL-style iterator for the first item with a key and iterate from there:</p>
<pre class="cpp">
<span class="type"><a href="qmultihash.html#QMultiHash">QMultiHash</a></span><span class="operator"><</span><span class="type"><a href="qstring.html">QString</a></span><span class="operator">,</span> <span class="type">int</span><span class="operator">></span><span class="operator">::</span>iterator i <span class="operator">=</span> hash<span class="operator">.</span>find(<span class="string">"plenty"</span>);
<span class="keyword">while</span> (i <span class="operator">!</span><span class="operator">=</span> hash<span class="operator">.</span>end() <span class="operator">&</span><span class="operator">&</span> i<span class="operator">.</span>key() <span class="operator">=</span><span class="operator">=</span> <span class="string">"plenty"</span>) {
cout <span class="operator"><</span><span class="operator"><</span> i<span class="operator">.</span>value() <span class="operator"><</span><span class="operator"><</span> endl;
<span class="operator">+</span><span class="operator">+</span>i;
}
</pre>
<p><a href="qmultihash.html">QMultiHash</a>'s key and value data types must be <a href="containers.html#assignable-data-types">assignable data types</a>. You cannot, for example, store a <a href="../qtwidgets/qwidget.html">QWidget</a> as a value; instead, store a <a href="../qtwidgets/qwidget.html">QWidget</a> *. In addition, <a href="qmultihash.html">QMultiHash</a>'s key type must provide operator==(), and there must also be a <a href="qmultihash.html#qHash">qHash</a>() function in the type's namespace that returns a hash value for an argument of the key's type. See the <a href="qhash.html#qhash">QHash</a> documentation for details.</p>
</div>
<p><b>See also </b><a href="qhash.html#qhash">QHash</a>, <a href="qhashiterator.html">QHashIterator</a>, <a href="qmutablehashiterator.html">QMutableHashIterator</a>, and <a href="qmultimap.html">QMultiMap</a>.</p>
<!-- @@@QMultiHash -->
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QMultiHash[overload1]$$$QMultiHash -->
<h3 class="fn" id="QMultiHash"><a name="QMultiHash"></a>QMultiHash::<span class="name">QMultiHash</span>()</h3>
<p>Constructs an empty hash.</p>
<!-- @@@QMultiHash -->
<!-- $$$QMultiHash$$$QMultiHashstd::initializer_list<std::pair<Key,T>> -->
<h3 class="fn" id="QMultiHash-1"><a name="QMultiHash-1"></a>QMultiHash::<span class="name">QMultiHash</span>(<span class="type">std::initializer_list</span><<span class="type">std::pair</span><<span class="type">Key</span>, <span class="type">T</span>> > <i>list</i>)</h3>
<p>Constructs a multi-hash with a copy of each of the elements in the initializer list <i>list</i>.</p>
<p>This function is only available if the program is being compiled in C++11 mode.</p>
<p>This function was introduced in Qt 5.1.</p>
<!-- @@@QMultiHash -->
<!-- $$$QMultiHash$$$QMultiHashconstQHash<Key,T>& -->
<h3 class="fn" id="QMultiHash-2"><a name="QMultiHash-2"></a>QMultiHash::<span class="name">QMultiHash</span>(const <span class="type"><a href="qhash.html#QHashx">QHash</a></span><<span class="type">Key</span>, <span class="type">T</span>> &<i>other</i>)</h3>
<p>Constructs a copy of <i>other</i> (which can be a <a href="qhash.html#qhash">QHash</a> or a <a href="qmultihash.html">QMultiHash</a>).</p>
<p><b>See also </b><a href="qhash.html#operator-eq">operator=</a>().</p>
<!-- @@@QMultiHash -->
<!-- $$$QMultiHash$$$QMultiHashQHash<Key,T>&& -->
<h3 class="fn" id="QMultiHash-3"><a name="QMultiHash-3"></a>QMultiHash::<span class="name">QMultiHash</span>(<span class="type"><a href="qhash.html#QHashx">QHash</a></span><<span class="type">Key</span>, <span class="type">T</span>> &&<i>other</i>)</h3>
<p>Default constructs an instance of QMultiHash.</p><!-- @@@QMultiHash -->
<!-- $$$constFind[overload1]$$$constFindconstKey&constT& -->
<h3 class="fn" id="constFind"><a name="constFind"></a><span class="type"><a href="qhash.html#QHashx">QHash</a></span><<span class="type">Key</span>, <span class="type">T</span>><span class="type">::const_iterator</span> QMultiHash::<span class="name">constFind</span>(const <span class="type">Key</span> &<i>key</i>, const <span class="type">T</span> &<i>value</i>) const</h3>
<p>Returns an iterator pointing to the item with the <i>key</i> and the <i>value</i> in the hash.</p>
<p>If the hash contains no such item, the function returns <a href="qhash.html#constEnd">constEnd</a>().</p>
<p>This function was introduced in Qt 4.3.</p>
<p><b>See also </b><a href="qhash.html#constFind">QHash::constFind</a>().</p>
<!-- @@@constFind -->
<!-- $$$contains[overload1]$$$containsconstKey&constT& -->
<h3 class="fn" id="contains"><a name="contains"></a><span class="type">bool</span> QMultiHash::<span class="name">contains</span>(const <span class="type">Key</span> &<i>key</i>, const <span class="type">T</span> &<i>value</i>) const</h3>
<p>Returns <code>true</code> if the hash contains an item with the <i>key</i> and <i>value</i>; otherwise returns <code>false</code>.</p>
<p>This function was introduced in Qt 4.3.</p>
<p><b>See also </b><a href="qhash.html#contains">QHash::contains</a>().</p>
<!-- @@@contains -->
<!-- $$$count[overload1]$$$countconstKey&constT& -->
<h3 class="fn" id="count"><a name="count"></a><span class="type">int</span> QMultiHash::<span class="name">count</span>(const <span class="type">Key</span> &<i>key</i>, const <span class="type">T</span> &<i>value</i>) const</h3>
<p>Returns the number of items with the <i>key</i> and <i>value</i>.</p>
<p>This function was introduced in Qt 4.3.</p>
<p><b>See also </b><a href="qhash.html#count-1">QHash::count</a>().</p>
<!-- @@@count -->
<!-- $$$find[overload1]$$$findconstKey&constT& -->
<h3 class="fn" id="find"><a name="find"></a><span class="type"><a href="qhash.html#QHashx">QHash</a></span><<span class="type">Key</span>, <span class="type">T</span>><span class="type">::iterator</span> QMultiHash::<span class="name">find</span>(const <span class="type">Key</span> &<i>key</i>, const <span class="type">T</span> &<i>value</i>)</h3>
<p>Returns an iterator pointing to the item with the <i>key</i> and <i>value</i>. If the hash contains no such item, the function returns <a href="qhash.html#end">end</a>().</p>
<p>If the hash contains multiple items with the <i>key</i> and <i>value</i>, the iterator returned points to the most recently inserted item.</p>
<p>This function was introduced in Qt 4.3.</p>
<p><b>See also </b><a href="qhash.html#find">QHash::find</a>().</p>
<!-- @@@find -->
<!-- $$$find$$$findconstKey&constT& -->
<h3 class="fn" id="find-1"><a name="find-1"></a><span class="type"><a href="qhash.html#QHashx">QHash</a></span><<span class="type">Key</span>, <span class="type">T</span>><span class="type">::const_iterator</span> QMultiHash::<span class="name">find</span>(const <span class="type">Key</span> &<i>key</i>, const <span class="type">T</span> &<i>value</i>) const</h3>
<p>This is an overloaded function.</p>
<p>This function was introduced in Qt 4.3.</p>
<!-- @@@find -->
<!-- $$$insert[overload1]$$$insertconstKey&constT& -->
<h3 class="fn" id="insert"><a name="insert"></a><span class="type"><a href="qhash.html#QHashx">QHash</a></span><<span class="type">Key</span>, <span class="type">T</span>><span class="type">::iterator</span> QMultiHash::<span class="name">insert</span>(const <span class="type">Key</span> &<i>key</i>, const <span class="type">T</span> &<i>value</i>)</h3>
<p>Inserts a new item with the <i>key</i> and a value of <i>value</i>.</p>
<p>If there is already an item with the same key in the hash, this function will simply create a new one. (This behavior is different from <a href="qmultihash.html#replace">replace</a>(), which overwrites the value of an existing item.)</p>
<p><b>See also </b><a href="qmultihash.html#replace">replace</a>().</p>
<!-- @@@insert -->
<!-- $$$remove[overload1]$$$removeconstKey&constT& -->
<h3 class="fn" id="remove"><a name="remove"></a><span class="type">int</span> QMultiHash::<span class="name">remove</span>(const <span class="type">Key</span> &<i>key</i>, const <span class="type">T</span> &<i>value</i>)</h3>
<p>Removes all the items that have the <i>key</i> and the value <i>value</i> from the hash. Returns the number of items removed.</p>
<p>This function was introduced in Qt 4.3.</p>
<p><b>See also </b><a href="qhash.html#remove">QHash::remove</a>().</p>
<!-- @@@remove -->
<!-- $$$replace[overload1]$$$replaceconstKey&constT& -->
<h3 class="fn" id="replace"><a name="replace"></a><span class="type"><a href="qhash.html#QHashx">QHash</a></span><<span class="type">Key</span>, <span class="type">T</span>><span class="type">::iterator</span> QMultiHash::<span class="name">replace</span>(const <span class="type">Key</span> &<i>key</i>, const <span class="type">T</span> &<i>value</i>)</h3>
<p>Inserts a new item with the <i>key</i> and a value of <i>value</i>.</p>
<p>If there is already an item with the <i>key</i>, that item's value is replaced with <i>value</i>.</p>
<p>If there are multiple items with the <i>key</i>, the most recently inserted item's value is replaced with <i>value</i>.</p>
<p><b>See also </b><a href="qmultihash.html#insert">insert</a>().</p>
<!-- @@@replace -->
<!-- $$$swap[overload1]$$$swapQMultiHash& -->
<h3 class="fn" id="swap"><a name="swap"></a><span class="type">void</span> QMultiHash::<span class="name">swap</span>(<span class="type"><a href="qmultihash.html#QMultiHash">QMultiHash</a></span> &<i>other</i>)</h3>
<p>Swaps hash <i>other</i> with this hash. This operation is very fast and never fails.</p>
<p>This function was introduced in Qt 4.8.</p>
<!-- @@@swap -->
<!-- $$$operator+[overload1]$$$operator+constQMultiHash& -->
<h3 class="fn" id="operator-2b"><a name="operator-2b"></a><span class="type"><a href="qmultihash.html#QMultiHash">QMultiHash</a></span> QMultiHash::<span class="name">operator+</span>(const <span class="type"><a href="qmultihash.html#QMultiHash">QMultiHash</a></span> &<i>other</i>) const</h3>
<p>Returns a hash that contains all the items in this hash in addition to all the items in <i>other</i>. If a key is common to both hashes, the resulting hash will contain the key multiple times.</p>
<p><b>See also </b><a href="qmultihash.html#operator-2b-eq">operator+=</a>().</p>
<!-- @@@operator+ -->
<!-- $$$operator+=[overload1]$$$operator+=constQMultiHash& -->
<h3 class="fn" id="operator-2b-eq"><a name="operator-2b-eq"></a><span class="type"><a href="qmultihash.html#QMultiHash">QMultiHash</a></span> &QMultiHash::<span class="name">operator+=</span>(const <span class="type"><a href="qmultihash.html#QMultiHash">QMultiHash</a></span> &<i>other</i>)</h3>
<p>Inserts all the items in the <i>other</i> hash into this hash and returns a reference to this hash.</p>
<p><b>See also </b><a href="qmultihash.html#insert">insert</a>().</p>
<!-- @@@operator+= -->
</div>
<div class="relnonmem">
<h2>Related Non-Members</h2>
<!-- $$$qHash[overload1]$$$qHashconstQMultiHash<Key,T>&uint -->
<h3 class="fn" id="qHash"><a name="qHash"></a><span class="type"><a href="qtglobal.html#uint-typedef">uint</a></span> <span class="name">qHash</span>(const <span class="type"><a href="qmultihash.html#QMultiHash">QMultiHash</a></span><<span class="type">Key</span>, <span class="type">T</span>> &<i>key</i>, <span class="type"><a href="qtglobal.html#uint-typedef">uint</a></span> <i>seed</i> = 0)</h3>
<p>Returns the hash value for the <i>key</i>, using <i>seed</i> to seed the calculation.</p>
<p>Type <code>T</code> must be supported by <a href="qhash.html#qHash">qHash</a>().</p>
<p>This function was introduced in Qt 5.8.</p>
<!-- @@@qHash -->
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<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
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