<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- qxmlresultitems.cpp --> <title>QXmlResultItems Class | Qt XML Patterns 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="qtxmlpatterns-index.html">Qt XML Patterns</a></td><td ><a href="qtxmlpatterns-module.html">C++ Classes</a></td><td >QXmlResultItems</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">QXmlResultItems Class</h1> <!-- $$$QXmlResultItems-brief --> <p>The <a href="qxmlresultitems.html">QXmlResultItems</a> class iterates through the results of evaluating an <a href="xmlprocessing.html">XQuery</a> in <a href="qxmlquery.html">QXmlQuery</a>. <a href="#details">More...</a></p> <!-- @@@QXmlResultItems --> <div class="table"><table class="alignedsummary"> <tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QXmlResultItems></span> </td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += xmlpatterns</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Since:</td><td class="memItemRight bottomAlign"> Qt 4.4</td></tr></table></div><ul> <li><a href="qxmlresultitems-members.html">List of all members, including inherited members</a></li> </ul> <p><b>Note:</b> All functions in this class are reentrant.</p> <a name="public-functions"></a> <h2 id="public-functions">Public Functions</h2> <div class="table"><table class="alignedsummary"> <tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qxmlresultitems.html#QXmlResultItems">QXmlResultItems</a></b>()</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> virtual </td><td class="memItemRight bottomAlign"><b><a href="qxmlresultitems.html#dtor.QXmlResultItems">~QXmlResultItems</a></b>()</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> QXmlItem </td><td class="memItemRight bottomAlign"><b><a href="qxmlresultitems.html#current">current</a></b>() const</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qxmlresultitems.html#hasError">hasError</a></b>() const</td></tr> <tr><td class="memItemLeft rightAlign topAlign"> QXmlItem </td><td class="memItemRight bottomAlign"><b><a href="qxmlresultitems.html#next">next</a></b>()</td></tr> </table></div> <a name="details"></a> <!-- $$$QXmlResultItems-description --> <div class="descr"> <h2 id="details">Detailed Description</h2> <p>The <a href="qxmlresultitems.html">QXmlResultItems</a> class iterates through the results of evaluating an <a href="xmlprocessing.html">XQuery</a> in <a href="qxmlquery.html">QXmlQuery</a>.</p> <p><a href="qxmlresultitems.html">QXmlResultItems</a> presents the evaluation of an associated query as a sequence of <a href="qxmlitem.html">QXmlItems</a>. The sequence is traversed by repeatedly calling <a href="qxmlresultitems.html#next">next</a>(), which actually produces the sequence by lazy evaluation of the query.</p> <pre class="cpp"> <span class="type"><a href="qxmlquery.html">QXmlQuery</a></span> query; query<span class="operator">.</span>setQuery(<span class="string">"<e/>, 1, 'two'"</span>); <span class="type"><a href="qxmlresultitems.html#QXmlResultItems">QXmlResultItems</a></span> result; <span class="keyword">if</span> (query<span class="operator">.</span>isValid()) { query<span class="operator">.</span>evaluateTo(<span class="operator">&</span>result); <span class="type"><a href="qxmlitem.html">QXmlItem</a></span> item(result<span class="operator">.</span>next()); <span class="keyword">while</span> (<span class="operator">!</span>item<span class="operator">.</span>isNull()) { <span class="comment">// use item</span> item <span class="operator">=</span> result<span class="operator">.</span>next(); } <span class="keyword">if</span> (result<span class="operator">.</span>hasError()) { <span class="comment">/* Runtime error! */</span> } } </pre> <p>An effect of letting <a href="qxmlresultitems.html#next">next</a>() produce the sequence by lazy evaluation is that a query error can occur on any call to <a href="qxmlresultitems.html#next">next</a>(). If an error occurs, both <a href="qxmlresultitems.html#next">next</a>() and <a href="qxmlresultitems.html#current">current</a>() will return the null <a href="qxmlitem.html">QXmlItem</a>, and <a href="qxmlresultitems.html#hasError">hasError</a>() will return true.</p> <p><a href="qxmlresultitems.html">QXmlResultItems</a> can be thought of as an "iterator" that traverses the sequence of query results once, in the forward direction. Each call to <a href="qxmlresultitems.html#next">next</a>() advances the iterator to the next <a href="qxmlitem.html">QXmlItem</a> in the sequence and returns it, and <a href="qxmlresultitems.html#current">current</a>() always returns the <a href="qxmlitem.html">QXmlItem</a> that <a href="qxmlresultitems.html#next">next</a>() returned the last time it was called.</p> <p><b>Note: </b>When using the <a href="qxmlresultitems.html">QXmlResultItems</a> overload of <a href="qxmlquery.html#evaluateTo">QXmlQuery::evaluateTo</a>() to execute a query, it is advisable to create a new instance of this class for each new set of results rather than reusing an old instance.</p></div> <p><b>See also </b><a href="qxmlitem.html#isNode">QXmlItem::isNode</a>(), <a href="qxmlitem.html#isAtomicValue">QXmlItem::isAtomicValue</a>(), and <a href="qxmlnodemodelindex.html">QXmlNodeModelIndex</a>.</p> <!-- @@@QXmlResultItems --> <div class="func"> <h2>Member Function Documentation</h2> <!-- $$$QXmlResultItems[overload1]$$$QXmlResultItems --> <h3 class="fn" id="QXmlResultItems"><a name="QXmlResultItems"></a>QXmlResultItems::<span class="name">QXmlResultItems</span>()</h3> <p>Constructs an instance of <a href="qxmlresultitems.html">QXmlResultItems</a>.</p> <!-- @@@QXmlResultItems --> <!-- $$$~QXmlResultItems[overload1]$$$~QXmlResultItems --> <h3 class="fn" id="dtor.QXmlResultItems"><a name="dtor.QXmlResultItems"></a><code>[virtual] </code>QXmlResultItems::<span class="name">~QXmlResultItems</span>()</h3> <p>Destroys this instance of <a href="qxmlresultitems.html">QXmlResultItems</a>.</p> <!-- @@@~QXmlResultItems --> <!-- $$$current[overload1]$$$current --> <h3 class="fn" id="current"><a name="current"></a><span class="type"><a href="qxmlitem.html">QXmlItem</a></span> QXmlResultItems::<span class="name">current</span>() const</h3> <p>Returns the current item. The current item is the last item that was produced and returned by <a href="qxmlresultitems.html#next">next</a>().</p> <p>Returns a null <a href="qxmlitem.html">QXmlItem</a> if there is no associated <a href="qxmlquery.html">QXmlQuery</a>.</p> <!-- @@@current --> <!-- $$$hasError[overload1]$$$hasError --> <h3 class="fn" id="hasError"><a name="hasError"></a><span class="type">bool</span> QXmlResultItems::<span class="name">hasError</span>() const</h3> <p>If an error occurred during evaluation of the query, true is returned.</p> <p>Returns false if query evaluation has been done.</p> <!-- @@@hasError --> <!-- $$$next[overload1]$$$next --> <h3 class="fn" id="next"><a name="next"></a><span class="type"><a href="qxmlitem.html">QXmlItem</a></span> QXmlResultItems::<span class="name">next</span>()</h3> <p>Returns the next result in the sequence produced by lazy evaluation of the associated query. When the returned <a href="qxmlitem.html">QXmlItem</a> is null, either the evaluation terminated normally without producing another result, or an error occurred. Call <a href="qxmlresultitems.html#hasError">hasError</a>() to determine whether the null item was caused by normal termination or by an error.</p> <p>Returns a null <a href="qxmlitem.html">QXmlItem</a> if there is no associated <a href="qxmlquery.html">QXmlQuery</a>.</p> <!-- @@@next --> </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. 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