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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en_US" lang="en_US">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- qdeclarativexmllistmodel.cpp -->
<title>Qt 4.8: QML XmlRole Element</title>
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<div class="header" id="qtdocheader">
<div class="content">
<a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
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<ul>
<li class="first"><a href="index.html">Home</a></li>
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<li><a href="qdeclarativeelements.html">QML Elements</a></li>
<li>QML XmlRole Element</li>
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<div class="content mainContent">
<div class="toc">
<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#properties">Properties</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
</ul>
</div>
<h1 class="title">QML XmlRole Element</h1>
<span class="subtitle"></span>
<!-- $$$XmlRole-brief -->
<p>The XmlRole element allows you to specify a role for an <a href="qml-xmllistmodel.html">XmlListModel</a>. <a href="#details">More...</a></p>
<!-- @@@XmlRole -->
<p>This element was introduced in Qt 4.7.</p>
<ul>
<li><a href="qml-xmlrole-members.html">List of all members, including inherited members</a></li>
</ul>
<a name="properties"></a>
<h2>Properties</h2>
<ul>
<li class="fn"><b><b><a href="qml-xmlrole.html#isKey-prop">isKey</a></b></b> : bool</li>
<li class="fn"><b><b><a href="qml-xmlrole.html#name-prop">name</a></b></b> : string</li>
<li class="fn"><b><b><a href="qml-xmlrole.html#query-prop">query</a></b></b> : string</li>
</ul>
<!-- $$$XmlRole-description -->
<a name="details"></a>
<h2>Detailed Description</h2>
<p><b>See also </b><a href="qtdeclarative.html">QtDeclarative</a>.</p>
<!-- @@@XmlRole -->
<h2>Property Documentation</h2>
<!-- $$$isKey -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="isKey-prop"></a><span class="name">isKey</span> : <span class="type"><a href="qml-bool.html">bool</a></span></p></td></tr></table></div><div class="qmldoc"><p>Defines whether this is a key role.</p>
<p>Key roles are used to to determine whether a set of values should be updated or added to the XML list model when <a href="qml-xmllistmodel.html#reload-method">XmlListModel::reload()</a> is called.</p>
<p><b>See also </b><a href="qml-xmllistmodel.html">XmlListModel</a>.</p>
</div></div><!-- @@@isKey -->
<br/>
<!-- $$$name -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="name-prop"></a><span class="name">name</span> : <span class="type"><a href="qml-string.html">string</a></span></p></td></tr></table></div><div class="qmldoc"><p>The name for the role. This name is used to access the model data for this role.</p>
<p>For example, the following model has a role named "title", which can be accessed from the view's delegate:</p>
<pre class="qml"> <span class="type"><a href="qml-xmllistmodel.html">XmlListModel</a></span> {
<span class="name">id</span>: <span class="name">xmlModel</span>
<span class="comment">// ...</span>
<span class="type"><a href="qml-xmlrole.html">XmlRole</a></span> {
<span class="name">name</span>: <span class="string">"title"</span>
<span class="name">query</span>: <span class="string">"title/string()"</span>
}
}</pre>
<pre class="qml"> <span class="type"><a href="qml-listview.html">ListView</a></span> {
<span class="name">model</span>: <span class="name">xmlModel</span>
<span class="name">delegate</span>: <span class="name">Text</span> { <span class="name">text</span>: <span class="name">title</span> }
}</pre>
</div></div><!-- @@@name -->
<br/>
<!-- $$$query -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="query-prop"></a><span class="name">query</span> : <span class="type"><a href="qml-string.html">string</a></span></p></td></tr></table></div><div class="qmldoc"><p>The relative XPath expression query for this role. The query must be relative; it cannot start with a '/'.</p>
<p>For example, if there is an XML document like this:</p>
<pre class="cpp"> <?xml version="1.0" encoding="iso-8859-1" ?>
<catalogue>
<book type="Hardcover">
<title>C++ GUI Programming with Qt 4</title>
<year>2006</year>
<author>Jasmin Blanchette</author>
<author>Mark Summerfield</author>
</book>
<book type="Paperback">
<title>Programming with Qt</title>
<year>2002</year>
<author>Matthias Kalle Dalheimer</author>
</book>
</catalogue></pre>
<p>Here are some valid XPath expressions for <a href="qml-xmlrole.html">XmlRole</a> queries on this document:</p>
<pre class="qml"> <span class="type"><a href="qml-xmllistmodel.html">XmlListModel</a></span> {
<span class="name">id</span>: <span class="name">model</span>
...
<span class="comment">// XmlRole queries will be made on <book> elements</span>
<span class="name">query</span>: <span class="string">"/catalogue/book"</span>
<span class="comment">// query the book title</span>
<span class="type"><a href="qml-xmlrole.html">XmlRole</a></span> { <span class="name">name</span>: <span class="string">"title"</span>; <span class="name">query</span>: <span class="string">"title/string()"</span> }
<span class="comment">// query the book's year</span>
<span class="type"><a href="qml-xmlrole.html">XmlRole</a></span> { <span class="name">name</span>: <span class="string">"year"</span>; <span class="name">query</span>: <span class="string">"year/number()"</span> }
<span class="comment">// query the book's type (the '@' indicates 'type' is an attribute, not an element)</span>
<span class="type"><a href="qml-xmlrole.html">XmlRole</a></span> { <span class="name">name</span>: <span class="string">"type"</span>; <span class="name">query</span>: <span class="string">"@type/string()"</span> }
<span class="comment">// query the book's first listed author (note in XPath the first index is 1, not 0)</span>
<span class="type"><a href="qml-xmlrole.html">XmlRole</a></span> { <span class="name">name</span>: <span class="string">"first_author"</span>; <span class="name">query</span>: <span class="string">"author[1]/string()"</span> }
}</pre>
<p>See the <a href="http://www.w3.org/TR/xpath20/">W3C XPath 2.0 specification</a> for more information.</p>
</div></div><!-- @@@query -->
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