<?xml version="1.0" encoding="iso-8859-1"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "DTD/xhtml1-strict.dtd"> <html><head><title>QXmlResultItems Class Reference</title><style>h3.fn,span.fn { margin-left: 1cm; text-indent: -1cm } a:link { color: #004faf; text-decoration: none } a:visited { color: #672967; text-decoration: none } td.postheader { font-family: sans-serif } tr.address { font-family: sans-serif } body { background: #ffffff; color: black; } </style></head><body><table border="0" cellpadding="0" cellspacing="0" width="100%"><tr /><td align="left" valign="top" width="32"><img align="left" border="0" height="32" src="images/rb-logo.png" width="32" /></td><td width="1">  </td><td class="postheader" valign="center"><a href="index.html"><font color="#004faf">Home</font></a> · <a href="classes.html"><font color="#004faf">All Classes</font></a> · <a href="modules.html"><font color="#004faf">Modules</font></a></td></table><h1 align="center">QXmlResultItems Class Reference<br /><sup><sup>[<a href="qtxmlpatterns.html">QtXmlPatterns</a> module]</sup></sup></h1><p>The QXmlResultItems 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> <h3>Methods</h3><ul><li><div class="fn" /><b><a href="qxmlresultitems.html#QXmlResultItems">__init__</a></b> (<i>self</i>)</li><li><div class="fn" />QXmlItem <b><a href="qxmlresultitems.html#current">current</a></b> (<i>self</i>)</li><li><div class="fn" />bool <b><a href="qxmlresultitems.html#hasError">hasError</a></b> (<i>self</i>)</li><li><div class="fn" />QXmlItem <b><a href="qxmlresultitems.html#next">next</a></b> (<i>self</i>)</li></ul><a name="details" /><hr /><h2>Detailed Description</h2><p>The QXmlResultItems class iterates through the results of evaluating an <a href="xmlprocessing.html">XQuery</a> in <a href="qxmlquery.html">QXmlQuery</a>.</p> <p>QXmlResultItems 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">QXmlResultItems</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>QXmlResultItems 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 QXmlResultItems 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> <hr /><h2>Method Documentation</h2><h3 class="fn"><a name="QXmlResultItems" />QXmlResultItems.__init__ (<i>self</i>)</h3><p>Constructs an instance of <a href="qxmlresultitems.html">QXmlResultItems</a>.</p> <h3 class="fn"><a name="current" /><a href="qxmlitem.html">QXmlItem</a> QXmlResultItems.current (<i>self</i>)</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> <h3 class="fn"><a name="hasError" />bool QXmlResultItems.hasError (<i>self</i>)</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> <h3 class="fn"><a name="next" /><a href="qxmlitem.html">QXmlItem</a> QXmlResultItems.next (<i>self</i>)</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> <address><hr /><div align="center"><table border="0" cellspacing="0" width="100%"><tr class="address"><td align="left" width="25%">PyQt 4.10.3 for X11</td><td align="center" width="50%">Copyright © <a href="http://www.riverbankcomputing.com">Riverbank Computing Ltd</a> and <a href="http://www.qtsoftware.com">Nokia</a> 2012</td><td align="right" width="25%">Qt 4.8.5</td></tr></table></div></address></body></html>