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Breadcrumbs go here --> <li><a href="modules.html">Modules</a></li> <li><a href="qtcore.html">QtCore</a></li> <li>const_iterator</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">const_iterator Class Reference</h1> <span class="small-subtitle">(QHash::const_iterator)<br/></span> <!-- $$$const_iterator-brief --> <p>The QHash::const_iterator class provides an STL-style const iterator for <a href="qhash.html">QHash</a> and <a href="qmultihash.html">QMultiHash</a>. <a href="#details">More...</a></p> <!-- @@@const_iterator --> <pre class="cpp"> <span class="preprocessor">#include <<a href="qhash.html">QHash</a>></span></pre><ul> <li><a href="qhash-const-iterator-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="qhash-const-iterator.html#const_iterator">const_iterator</a></b> ()</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#const_iterator-3">const_iterator</a></b> ( const iterator & <i>other</i> )</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> const Key & </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#key">key</a></b> () const</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> const T & </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#value">value</a></b> () const</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#operator-not-eq">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="qhash-const-iterator.html#operator-2a">operator*</a></b> () const</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> const_iterator </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#operator-2b">operator+</a></b> ( int <i>j</i> ) const</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> const_iterator & </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#operator-2b-2b">operator++</a></b> ()</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> const_iterator </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#operator-2b-2b-2">operator++</a></b> ( int )</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> const_iterator & </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#operator-2b-eq">operator+=</a></b> ( int <i>j</i> )</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> const_iterator </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#operator-">operator-</a></b> ( int <i>j</i> ) const</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> const_iterator & </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#operator--">operator--</a></b> ()</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> const_iterator </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#operator---2">operator--</a></b> ( int )</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> const_iterator & </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-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="qhash-const-iterator.html#operator--gt">operator-></a></b> () const</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qhash-const-iterator.html#operator-eq-eq">operator==</a></b> ( const const_iterator & <i>other</i> ) const</td></tr> </table> <a name="details"></a> <!-- $$$const_iterator-description --> <div class="descr"> <h2>Detailed Description</h2> <p>The QHash::const_iterator class provides an STL-style const iterator for <a href="qhash.html">QHash</a> and <a href="qmultihash.html">QMultiHash</a>.</p> <p><a href="qhash.html">QHash</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="qhash.html">QHash</a><Key, T>::const_iterator allows you to iterate over a <a href="qhash.html">QHash</a> (or a <a href="qmultihash.html">QMultiHash</a>). If you want to modify the <a href="qhash.html">QHash</a> as you iterate over it, you must use <a href="qhash-iterator.html">QHash::iterator</a> instead. It is generally good practice to use QHash::const_iterator on a non-const <a href="qhash.html">QHash</a> as well, unless you need to change the <a href="qhash.html">QHash</a> through the iterator. Const iterators are slightly faster, and can improve code readability.</p> <p>The default QHash::const_iterator constructor creates an uninitialized iterator. You must initialize it using a <a href="qhash.html">QHash</a> function like <a href="qhash.html#constBegin">QHash::constBegin</a>(), <a href="qhash.html#constEnd">QHash::constEnd</a>(), or <a href="qhash.html#find">QHash::find</a>() before you can start iterating. Here's a typical loop that prints all the (key, value) pairs stored in a hash:</p> <pre class="cpp"> <span class="type"><a href="qhash.html">QHash</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> hash; hash<span class="operator">.</span><a href="qhash.html#insert">insert</a>(<span class="string">"January"</span><span class="operator">,</span> <span class="number">1</span>); hash<span class="operator">.</span><a href="qhash.html#insert">insert</a>(<span class="string">"February"</span><span class="operator">,</span> <span class="number">2</span>); <span class="operator">.</span><span class="operator">.</span><span class="operator">.</span> hash<span class="operator">.</span><a href="qhash.html#insert">insert</a>(<span class="string">"December"</span><span class="operator">,</span> <span class="number">12</span>); <span class="type"><a href="qhash.html">QHash</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>const_iterator i; <span class="keyword">for</span> (i <span class="operator">=</span> hash<span class="operator">.</span>constBegin(); i <span class="operator">!</span><span class="operator">=</span> hash<span class="operator">.</span>constEnd(); <span class="operator">+</span><span class="operator">+</span>i) cout <span class="operator"><</span><span class="operator"><</span> i<span class="operator">.</span><a href="qhash-const-iterator.html#key">key</a>() <span class="operator"><</span><span class="operator"><</span> <span class="string">": "</span> <span class="operator"><</span><span class="operator"><</span> i<span class="operator">.</span><a href="qhash-const-iterator.html#value">value</a>() <span class="operator"><</span><span class="operator"><</span> endl;</pre> <p>Unlike <a href="qmap.html">QMap</a>, which orders its items by key, <a href="qhash.html">QHash</a> stores its items in an arbitrary order. The only guarantee is that items that share the same key (because they were inserted using <a href="qhash.html#insertMulti">QHash::insertMulti</a>()) will appear consecutively, from the most recently to the least recently inserted value.</p> <p>Multiple iterators can be used on the same hash. However, be aware that any modification performed directly on the <a href="qhash.html">QHash</a> has the potential of dramatically changing the order in which the items are stored in the hash, as they might cause <a href="qhash.html">QHash</a> to rehash its internal data structure. If you need to keep iterators over a long period of time, we recommend that you use <a href="qmap.html">QMap</a> rather than <a href="qhash.html">QHash</a>.</p> </div> <p><b>See also </b><a href="qhash-iterator.html">QHash::iterator</a> and <a href="qhashiterator.html">QHashIterator</a>.</p> <!-- @@@const_iterator --> <div class="func"> <h2>Member Function Documentation</h2> <!-- $$$const_iterator[overload1]$$$const_iterator --> <h3 class="fn"><a name="const_iterator"></a>const_iterator::<span class="name">const_iterator</span> ()</h3> <p>Constructs an uninitialized iterator.</p> <p>Functions like <a href="qhash-const-iterator.html#key">key</a>(), <a href="qhash-const-iterator.html#value">value</a>(), and operator++() must 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="qhash.html#constBegin">QHash::constBegin</a>() and <a href="qhash.html#constEnd">QHash::constEnd</a>().</p> <!-- @@@const_iterator --> <!-- $$$const_iterator$$$const_iteratorconstiterator& --> <h3 class="fn"><a name="const_iterator-3"></a>const_iterator::<span class="name">const_iterator</span> ( const <span class="type"><a href="qhash-iterator.html">iterator</a></span> & <i>other</i> )</h3> <p>Constructs a copy of <i>other</i>.</p> <!-- @@@const_iterator --> <!-- $$$key[overload1]$$$key --> <h3 class="fn"><a name="key"></a>const <span class="type">Key</span> & const_iterator::<span class="name">key</span> () const</h3> <p>Returns the current item's key.</p> <p><b>See also </b><a href="qhash-const-iterator.html#value">value</a>().</p> <!-- @@@key --> <!-- $$$value[overload1]$$$value --> <h3 class="fn"><a name="value"></a>const <span class="type">T</span> & const_iterator::<span class="name">value</span> () const</h3> <p>Returns the current item's value.</p> <p><b>See also </b><a href="qhash-const-iterator.html#key">key</a>() and <a href="qhash-const-iterator.html#operator-2a">operator*</a>().</p> <!-- @@@value --> <!-- $$$operator!=[overload1]$$$operator!=constconst_iterator& --> <h3 class="fn"><a name="operator-not-eq"></a><span class="type">bool</span> const_iterator::<span class="name">operator!=</span> ( const <span class="type">const_iterator</span> & <i>other</i> ) const</h3> <p>Returns true if <i>other</i> points to a different item than this iterator; otherwise returns false.</p> <p><b>See also </b><a href="qhash-const-iterator.html#operator-eq-eq">operator==</a>().</p> <!-- @@@operator!= --> <!-- $$$operator*[overload1]$$$operator* --> <h3 class="fn"><a name="operator-2a"></a>const <span class="type">T</span> & const_iterator::<span class="name">operator*</span> () const</h3> <p>Returns the current item's value.</p> <p>Same as <a href="qhash-const-iterator.html#value">value</a>().</p> <p><b>See also </b><a href="qhash-const-iterator.html#key">key</a>().</p> <!-- @@@operator* --> <!-- $$$operator+[overload1]$$$operator+int --> <h3 class="fn"><a name="operator-2b"></a><span class="type">const_iterator</span> const_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="qhash-const-iterator.html#operator-">operator-</a>().</p> <!-- @@@operator+ --> <!-- $$$operator++[overload1]$$$operator++ --> <h3 class="fn"><a name="operator-2b-2b"></a><span class="type">const_iterator</span> & const_iterator::<span class="name">operator++</span> ()</h3> <p>The prefix ++ operator (<tt>++i</tt>) advances the iterator to the next item in the hash and returns an iterator to the new current item.</p> <p>Calling this function on <a href="qhash.html#end">QHash::end</a>() leads to undefined results.</p> <p><b>See also </b><a href="qhash-const-iterator.html#operator--">operator--</a>().</p> <!-- @@@operator++ --> <!-- $$$operator++$$$operator++int --> <h3 class="fn"><a name="operator-2b-2b-2"></a><span class="type">const_iterator</span> const_iterator::<span class="name">operator++</span> ( <span class="type">int</span> )</h3> <p>This is an overloaded function.</p> <p>The postfix ++ operator (<tt>i++</tt>) advances the iterator to the next item in the hash and returns an iterator to the previously current item.</p> <!-- @@@operator++ --> <!-- $$$operator+=[overload1]$$$operator+=int --> <h3 class="fn"><a name="operator-2b-eq"></a><span class="type">const_iterator</span> & const_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="qhash-const-iterator.html#operator--eq">operator-=</a>() and <a href="qhash-const-iterator.html#operator-2b">operator+</a>().</p> <!-- @@@operator+= --> <!-- $$$operator-[overload1]$$$operator-int --> <h3 class="fn"><a name="operator-"></a><span class="type">const_iterator</span> const_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="qhash-const-iterator.html#operator-2b">operator+</a>().</p> <!-- @@@operator- --> <!-- $$$operator--[overload1]$$$operator-- --> <h3 class="fn"><a name="operator--"></a><span class="type">const_iterator</span> & const_iterator::<span class="name">operator--</span> ()</h3> <p>The prefix -- operator (<tt>--i</tt>) makes the preceding item current and returns an iterator pointing to the new current item.</p> <p>Calling this function on <a href="qhash.html#begin">QHash::begin</a>() leads to undefined results.</p> <p><b>See also </b><a href="qhash-const-iterator.html#operator-2b-2b">operator++</a>().</p> <!-- @@@operator-- --> <!-- $$$operator--$$$operator--int --> <h3 class="fn"><a name="operator---2"></a><span class="type">const_iterator</span> const_iterator::<span class="name">operator--</span> ( <span class="type">int</span> )</h3> <p>This is an overloaded function.</p> <p>The postfix -- operator (<tt>i--</tt>) makes the preceding item current and returns an iterator pointing to the previously current item.</p> <!-- @@@operator-- --> <!-- $$$operator-=[overload1]$$$operator-=int --> <h3 class="fn"><a name="operator--eq"></a><span class="type">const_iterator</span> & const_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="qhash-const-iterator.html#operator-2b-eq">operator+=</a>() and <a href="qhash-const-iterator.html#operator-">operator-</a>().</p> <!-- @@@operator-= --> <!-- $$$operator->[overload1]$$$operator-> --> <h3 class="fn"><a name="operator--gt"></a>const <span class="type">T</span> * const_iterator::<span class="name">operator-></span> () const</h3> <p>Returns a pointer to the current item's value.</p> <p><b>See also </b><a href="qhash-const-iterator.html#value">value</a>().</p> <!-- @@@operator-> --> <!-- $$$operator==[overload1]$$$operator==constconst_iterator& --> <h3 class="fn"><a name="operator-eq-eq"></a><span class="type">bool</span> const_iterator::<span class="name">operator==</span> ( const <span class="type">const_iterator</span> & <i>other</i> ) const</h3> <p>Returns true if <i>other</i> points to the same item as this iterator; otherwise returns false.</p> <p><b>See also </b><a href="qhash-const-iterator.html#operator-not-eq">operator!=</a>().</p> <!-- @@@operator== --> </div> </div> </div> </div> <div class="ft"> <span></span> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2015 The Qt Company Ltd. 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