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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" />
<!-- qdeclarativevisualitemmodel.cpp -->
<title>Qt 4.8: QML VisualDataModel Element</title>
<link rel="stylesheet" type="text/css" href="style/offline.css" />
</head>
<body>
<div class="header" id="qtdocheader">
<div class="content">
<a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
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<div class="breadcrumb toolblock">
<ul>
<li class="first"><a href="index.html">Home</a></li>
<!-- Breadcrumbs go here -->
<li><a href="qdeclarativeelements.html">QML Elements</a></li>
<li>QML VisualDataModel Element</li>
</ul>
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</div>
<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="#methods">Methods</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
</ul>
</div>
<h1 class="title">QML VisualDataModel Element</h1>
<span class="subtitle"></span>
<!-- $$$VisualDataModel-brief -->
<p>The VisualDataModel encapsulates a model and delegate <a href="#details">More...</a></p>
<!-- @@@VisualDataModel -->
<ul>
<li><a href="qml-visualdatamodel-members.html">List of all members, including inherited members</a></li>
</ul>
<a name="properties"></a>
<h2>Properties</h2>
<ul>
<li class="fn"><b><b><a href="qml-visualdatamodel.html#delegate-prop">delegate</a></b></b> : Component</li>
<li class="fn"><b><b><a href="qml-visualdatamodel.html#model-prop">model</a></b></b> : model</li>
<li class="fn"><b><b><a href="qml-visualdatamodel.html#parts-prop">parts</a></b></b> : object</li>
<li class="fn"><b><b><a href="qml-visualdatamodel.html#rootIndex-prop">rootIndex</a></b></b> : QModelIndex</li>
</ul>
<a name="methods"></a>
<h2>Methods</h2>
<ul>
<li class="fn"><b><b><a href="qml-visualdatamodel.html#modelIndex-method">modelIndex</a></b></b></li>
<li class="fn"><b><b><a href="qml-visualdatamodel.html#parentModelIndex-method">parentModelIndex</a></b></b></li>
</ul>
<!-- $$$VisualDataModel-description -->
<a name="details"></a>
<h2>Detailed Description</h2>
<p>A VisualDataModel encapsulates a model and the delegate that will be instantiated for items in the model.</p>
<p>It is usually not necessary to create VisualDataModel elements. However, it can be useful for manipulating and accessing the <a href="qml-visualdatamodel.html#modelIndex-method">modelIndex</a> when a <a href="qabstractitemmodel.html">QAbstractItemModel</a> subclass is used as the model. Also, VisualDataModel is used together with <a href="qml-package.html">Package</a> to provide delegates to multiple views.</p>
<p>The example below illustrates using a VisualDataModel with a <a href="qml-listview.html">ListView</a>.</p>
<pre class="qml"> import QtQuick 1.0
<span class="type"><a href="qml-rectangle.html">Rectangle</a></span> {
<span class="name">width</span>: <span class="number">200</span>; <span class="name">height</span>: <span class="number">100</span>
<span class="type">VisualDataModel</span> {
<span class="name">id</span>: <span class="name">visualModel</span>
<span class="name">model</span>: <span class="name">ListModel</span> {
<span class="type"><a href="qml-listelement.html">ListElement</a></span> { <span class="name">name</span>: <span class="string">"Apple"</span> }
<span class="type"><a href="qml-listelement.html">ListElement</a></span> { <span class="name">name</span>: <span class="string">"Orange"</span> }
}
<span class="name">delegate</span>: <span class="name">Rectangle</span> {
<span class="name">height</span>: <span class="number">25</span>
<span class="name">width</span>: <span class="number">100</span>
<span class="type"><a href="qml-text.html">Text</a></span> { <span class="name">text</span>: <span class="string">"Name: "</span> <span class="operator">+</span> <span class="name">name</span>}
}
}
<span class="type"><a href="qml-listview.html">ListView</a></span> {
<span class="name">anchors</span>.fill: <span class="name">parent</span>
<span class="name">model</span>: <span class="name">visualModel</span>
}
}</pre>
<!-- @@@VisualDataModel -->
<h2>Property Documentation</h2>
<!-- $$$delegate -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="delegate-prop"></a><span class="name">delegate</span> : <span class="type"><a href="qml-component.html">Component</a></span></p></td></tr></table></div><div class="qmldoc"><p>The delegate provides a template defining each item instantiated by a view. The index is exposed as an accessible <tt>index</tt> property. Properties of the model are also available depending upon the type of <a href="qdeclarativemodels.html#qmlmodels">Data Model</a>.</p>
</div></div><!-- @@@delegate -->
<br/>
<!-- $$$model -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="model-prop"></a><span class="name">model</span> : <span class="type">model</span></p></td></tr></table></div><div class="qmldoc"><p>This property holds the model providing data for the <a href="qml-visualdatamodel.html">VisualDataModel</a>.</p>
<p>The model provides a set of data that is used to create the items for a view. For large or dynamic datasets the model is usually provided by a C++ model object. The C++ model object must be a <a href="qabstractitemmodel.html">QAbstractItemModel</a> subclass or a simple list.</p>
<p>Models can also be created directly in QML, using a <a href="qml-listmodel.html">ListModel</a> or <a href="qml-xmllistmodel.html">XmlListModel</a>.</p>
<p><b>See also </b><a href="qdeclarativemodels.html#qmlmodels">Data Models</a>.</p>
</div></div><!-- @@@model -->
<br/>
<!-- $$$parts -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="parts-prop"></a><span class="qmlreadonly">read-only</span><span class="name">parts</span> : <span class="type">object</span></p></td></tr></table></div><div class="qmldoc"><p>The <i>parts</i> property selects a <a href="qml-visualdatamodel.html">VisualDataModel</a> which creates delegates from the part named. This is used in conjunction with the <a href="qml-package.html">Package</a> element.</p>
<p>For example, the code below selects a model which creates delegates named <i>list</i> from a <a href="qml-package.html">Package</a>:</p>
<pre class="cpp"> VisualDataModel {
id: visualModel
delegate: Package {
Item { Package<span class="operator">.</span>name: <span class="string">"list"</span> }
}
model: myModel
}
ListView {
width: <span class="number">200</span>; height:<span class="number">200</span>
model: visualModel<span class="operator">.</span>parts<span class="operator">.</span>list
}</pre>
<p><b>See also </b><a href="qml-package.html">Package</a>.</p>
</div></div><!-- @@@parts -->
<br/>
<!-- $$$rootIndex -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlPropNode"><p><a name="rootIndex-prop"></a><span class="name">rootIndex</span> : <span class="type"><a href="qmodelindex.html">QModelIndex</a></span></p></td></tr></table></div><div class="qmldoc"><p><a href="qabstractitemmodel.html">QAbstractItemModel</a> provides a hierarchical tree of data, whereas QML only operates on list data. <tt>rootIndex</tt> allows the children of any node in a <a href="qabstractitemmodel.html">QAbstractItemModel</a> to be provided by this model.</p>
<p>This property only affects models of type <a href="qabstractitemmodel.html">QAbstractItemModel</a> that are hierarchical (e.g, a tree model).</p>
<p>For example, here is a simple interactive file system browser. When a directory name is clicked, the view's <tt>rootIndex</tt> is set to the <a href="qmodelindex.html">QModelIndex</a> node of the clicked directory, thus updating the view to show the new directory's contents.</p>
<p><tt>main.cpp</tt>:</p>
<pre class="cpp"> <span class="type">int</span> main(<span class="type">int</span> argc<span class="operator">,</span> <span class="type">char</span> <span class="operator">*</span><span class="operator">*</span> argv)
{
<span class="type"><a href="qapplication.html">QApplication</a></span> app(argc<span class="operator">,</span> argv);
<span class="type"><a href="qdeclarativeview.html">QDeclarativeView</a></span> view;
<span class="type"><a href="qdirmodel.html">QDirModel</a></span> model;
view<span class="operator">.</span>rootContext()<span class="operator">-</span><span class="operator">></span>setContextProperty(<span class="string">"dirModel"</span><span class="operator">,</span> <span class="operator">&</span>model);
view<span class="operator">.</span>setSource(<span class="type"><a href="qurl.html">QUrl</a></span><span class="operator">::</span>fromLocalFile(<span class="string">"view.qml"</span>));
view<span class="operator">.</span>show();
<span class="keyword">return</span> app<span class="operator">.</span>exec();
}</pre>
<p><tt>view.qml</tt>:</p>
<pre class="qml"> import QtQuick 1.0
<span class="type"><a href="qml-listview.html">ListView</a></span> {
<span class="name">id</span>: <span class="name">view</span>
<span class="name">width</span>: <span class="number">300</span>
<span class="name">height</span>: <span class="number">400</span>
<span class="name">model</span>: <span class="name">VisualDataModel</span> {
<span class="name">model</span>: <span class="name">dirModel</span>
<span class="name">delegate</span>: <span class="name">Rectangle</span> {
<span class="name">width</span>: <span class="number">200</span>; <span class="name">height</span>: <span class="number">25</span>
<span class="type"><a href="qml-text.html">Text</a></span> { <span class="name">text</span>: <span class="name">filePath</span> }
<span class="type"><a href="qml-mousearea.html">MouseArea</a></span> {
<span class="name">anchors</span>.fill: <span class="name">parent</span>
<span class="name">onClicked</span>: {
<span class="keyword">if</span> (<span class="name">model</span>.<span class="name">hasModelChildren</span>)
<span class="name">view</span>.<span class="name">model</span>.<span class="name">rootIndex</span> <span class="operator">=</span> <span class="name">view</span>.<span class="name">model</span>.<span class="name">modelIndex</span>(<span class="name">index</span>)
}
}
}
}
}</pre>
<p>If the <a href="qml-visualdatamodel.html#model-prop">model</a> is a <a href="qabstractitemmodel.html">QAbstractItemModel</a> subclass, the delegate can also reference a <tt>hasModelChildren</tt> property (optionally qualified by a <i>model</i>. prefix) that indicates whether the delegate's model item has any child nodes.</p>
<p><b>See also </b><a href="qml-visualdatamodel.html#modelIndex-method">modelIndex()</a> and <a href="qml-visualdatamodel.html#parentModelIndex-method">parentModelIndex()</a>.</p>
</div></div><!-- @@@rootIndex -->
<br/>
<h2>Method Documentation</h2>
<!-- $$$modelIndex -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlFuncNode"><p><a name="modelIndex-method"></a><span class="type"><a href="qmodelindex.html">QModelIndex</a></span> VisualDataModel::<span class="name">modelIndex</span> ( <span class="type"><a href="qml-int.html">int</a></span> <i>index</i> )</p></td></tr></table></div><div class="qmldoc"><p><a href="qabstractitemmodel.html">QAbstractItemModel</a> provides a hierarchical tree of data, whereas QML only operates on list data. This function assists in using tree models in QML.</p>
<p>Returns a <a href="qmodelindex.html">QModelIndex</a> for the specified index. This value can be assigned to <a href="qml-visualdatamodel.html#rootIndex-prop">rootIndex</a>.</p>
<p><b>See also </b><a href="qml-visualdatamodel.html#rootIndex-prop">rootIndex</a>.</p>
</div></div><!-- @@@modelIndex -->
<br/>
<!-- $$$parentModelIndex -->
<div class="qmlitem"><div class="qmlproto"><table class="qmlname"><tr valign="top" class="odd"><td class="tblQmlFuncNode"><p><a name="parentModelIndex-method"></a><span class="type"><a href="qmodelindex.html">QModelIndex</a></span> VisualDataModel::<span class="name">parentModelIndex</span> ()</p></td></tr></table></div><div class="qmldoc"><p><a href="qabstractitemmodel.html">QAbstractItemModel</a> provides a hierarchical tree of data, whereas QML only operates on list data. This function assists in using tree models in QML.</p>
<p>Returns a <a href="qmodelindex.html">QModelIndex</a> for the parent of the current <a href="qml-visualdatamodel.html#rootIndex-prop">rootIndex</a>. This value can be assigned to <a href="qml-visualdatamodel.html#rootIndex-prop">rootIndex</a>.</p>
<p><b>See also </b><a href="qml-visualdatamodel.html#rootIndex-prop">rootIndex</a>.</p>
</div></div><!-- @@@parentModelIndex -->
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