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  <title>Qt 4.8: QDeclarativeListReference Class Reference</title>
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<h1 class="title">QDeclarativeListReference Class Reference</h1>
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<p>The QDeclarativeListReference class allows the manipulation of <a href="qdeclarativelistproperty.html">QDeclarativeListProperty</a> properties. <a href="#details">More...</a></p>
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<pre class="cpp"> <span class="preprocessor">#include &lt;QDeclarativeListReference&gt;</span></pre><p>This class was introduced in Qt 4.7.</p>
<ul>
<li><a href="qdeclarativelistreference-members.html">List of all members, including inherited members</a></li>
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<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="qdeclarativelistreference.html#QDeclarativeListReference">QDeclarativeListReference</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#QDeclarativeListReference-2">QDeclarativeListReference</a></b> ( QObject * <i>object</i>, const char * <i>property</i>, QDeclarativeEngine * <i>engine</i> = 0 )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#append">append</a></b> ( QObject * <i>object</i> ) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QObject * </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#at">at</a></b> ( int <i>index</i> ) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#canAppend">canAppend</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#canAt">canAt</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#canClear">canClear</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#canCount">canCount</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#clear">clear</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#count">count</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#isValid">isValid</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const QMetaObject * </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#listElementType">listElementType</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QObject * </td><td class="memItemRight bottomAlign"><b><a href="qdeclarativelistreference.html#object">object</a></b> () const</td></tr>
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<a name="details"></a>
<!-- $$$QDeclarativeListReference-description -->
<div class="descr">
<h2>Detailed Description</h2>
<p>The QDeclarativeListReference class allows the manipulation of <a href="qdeclarativelistproperty.html">QDeclarativeListProperty</a> properties.</p>
<p>QDeclarativeListReference allows C++ programs to read from, and assign values to a QML list property in a simple and type safe way. A QDeclarativeListReference can be created by passing an object and property name or through a <a href="qdeclarativeproperty.html">QDeclarativeProperty</a> instance. These two are equivalant:</p>
<pre class="cpp"> <span class="type">QDeclarativeListReference</span> ref1(object<span class="operator">,</span> <span class="string">&quot;children&quot;</span>);

 <span class="type"><a href="qdeclarativeproperty.html">QDeclarativeProperty</a></span> ref2(object<span class="operator">,</span> <span class="string">&quot;children&quot;</span>);
 <span class="type">QDeclarativeListReference</span> ref2 <span class="operator">=</span> qvariant_cast<span class="operator">&lt;</span><span class="type">QDeclarativeListReference</span><span class="operator">&gt;</span>(ref2<span class="operator">.</span>read());</pre>
<p>Not all QML list properties support all operations. A set of methods, <a href="qdeclarativelistreference.html#canAppend">canAppend</a>(), <a href="qdeclarativelistreference.html#canAt">canAt</a>(), <a href="qdeclarativelistreference.html#canClear">canClear</a>() and <a href="qdeclarativelistreference.html#canCount">canCount</a>() allow programs to query whether an operation is supported on a given property.</p>
<p>QML list properties are typesafe. Only <a href="qobject.html">QObject</a>'s that derive from the correct base class can be assigned to the list. The <a href="qdeclarativelistreference.html#listElementType">listElementType</a>() method can be used to query the <a href="qmetaobject.html">QMetaObject</a> of the <a href="qobject.html">QObject</a> type supported. Attempting to add objects of the incorrect type to a list property will fail.</p>
<p>Like with normal lists, when accessing a list element by index, it is the callers responsibility to ensure that it does not request an out of range element using the <a href="qdeclarativelistreference.html#count">count</a>() method before calling <a href="qdeclarativelistreference.html#at">at</a>().</p>
</div>
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<div class="func">
<h2>Member Function Documentation</h2>
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<h3 class="fn"><a name="QDeclarativeListReference"></a>QDeclarativeListReference::<span class="name">QDeclarativeListReference</span> ()</h3>
<p>Constructs an invalid instance.</p>
<!-- @@@QDeclarativeListReference -->
<!-- $$$QDeclarativeListReference$$$QDeclarativeListReferenceQObject*constchar*QDeclarativeEngine* -->
<h3 class="fn"><a name="QDeclarativeListReference-2"></a>QDeclarativeListReference::<span class="name">QDeclarativeListReference</span> ( <span class="type"><a href="qobject.html">QObject</a></span> * <i>object</i>, const <span class="type">char</span> * <i>property</i>, <span class="type"><a href="qdeclarativeengine.html">QDeclarativeEngine</a></span> * <i>engine</i> = 0 )</h3>
<p>Constructs a <a href="qdeclarativelistreference.html">QDeclarativeListReference</a> for <i>object</i>'s <i>property</i>. If <i>property</i> is not a list property, an invalid <a href="qdeclarativelistreference.html">QDeclarativeListReference</a> is created. If <i>object</i> is destroyed after the reference is constructed, it will automatically become invalid. That is, it is safe to hold <a href="qdeclarativelistreference.html">QDeclarativeListReference</a> instances even after <i>object</i> is deleted.</p>
<p>Passing <i>engine</i> is required to access some QML created list properties. If in doubt, and an engine is available, pass it.</p>
<!-- @@@QDeclarativeListReference -->
<!-- $$$append[overload1]$$$appendQObject* -->
<h3 class="fn"><a name="append"></a><span class="type">bool</span> QDeclarativeListReference::<span class="name">append</span> ( <span class="type"><a href="qobject.html">QObject</a></span> * <i>object</i> ) const</h3>
<p>Appends <i>object</i> to the list. Returns true if the operation succeeded, otherwise false.</p>
<p><b>See also </b><a href="qdeclarativelistreference.html#canAppend">canAppend</a>().</p>
<!-- @@@append -->
<!-- $$$at[overload1]$$$atint -->
<h3 class="fn"><a name="at"></a><span class="type"><a href="qobject.html">QObject</a></span> * QDeclarativeListReference::<span class="name">at</span> ( <span class="type">int</span> <i>index</i> ) const</h3>
<p>Returns the list element at <i>index</i>, or 0 if the operation failed.</p>
<p><b>See also </b><a href="qdeclarativelistreference.html#canAt">canAt</a>().</p>
<!-- @@@at -->
<!-- $$$canAppend[overload1]$$$canAppend -->
<h3 class="fn"><a name="canAppend"></a><span class="type">bool</span> QDeclarativeListReference::<span class="name">canAppend</span> () const</h3>
<p>Returns true if the list property can be appended to, otherwise false. Returns false if the reference is invalid.</p>
<p><b>See also </b><a href="qdeclarativelistreference.html#append">append</a>().</p>
<!-- @@@canAppend -->
<!-- $$$canAt[overload1]$$$canAt -->
<h3 class="fn"><a name="canAt"></a><span class="type">bool</span> QDeclarativeListReference::<span class="name">canAt</span> () const</h3>
<p>Returns true if the list property can queried by index, otherwise false. Returns false if the reference is invalid.</p>
<p><b>See also </b><a href="qdeclarativelistreference.html#at">at</a>().</p>
<!-- @@@canAt -->
<!-- $$$canClear[overload1]$$$canClear -->
<h3 class="fn"><a name="canClear"></a><span class="type">bool</span> QDeclarativeListReference::<span class="name">canClear</span> () const</h3>
<p>Returns true if the list property can be cleared, otherwise false. Returns false if the reference is invalid.</p>
<p><b>See also </b><a href="qdeclarativelistreference.html#clear">clear</a>().</p>
<!-- @@@canClear -->
<!-- $$$canCount[overload1]$$$canCount -->
<h3 class="fn"><a name="canCount"></a><span class="type">bool</span> QDeclarativeListReference::<span class="name">canCount</span> () const</h3>
<p>Returns true if the list property can be queried for its element count, otherwise false. Returns false if the reference is invalid.</p>
<p><b>See also </b><a href="qdeclarativelistreference.html#count">count</a>().</p>
<!-- @@@canCount -->
<!-- $$$clear[overload1]$$$clear -->
<h3 class="fn"><a name="clear"></a><span class="type">bool</span> QDeclarativeListReference::<span class="name">clear</span> () const</h3>
<p>Clears the list. Returns true if the operation succeeded, otherwise false.</p>
<p><b>See also </b><a href="qdeclarativelistreference.html#canClear">canClear</a>().</p>
<!-- @@@clear -->
<!-- $$$count[overload1]$$$count -->
<h3 class="fn"><a name="count"></a><span class="type">int</span> QDeclarativeListReference::<span class="name">count</span> () const</h3>
<p>Returns the number of objects in the list, or 0 if the operation failed.</p>
<!-- @@@count -->
<!-- $$$isValid[overload1]$$$isValid -->
<h3 class="fn"><a name="isValid"></a><span class="type">bool</span> QDeclarativeListReference::<span class="name">isValid</span> () const</h3>
<p>Returns true if the instance refers to a valid list property, otherwise false.</p>
<!-- @@@isValid -->
<!-- $$$listElementType[overload1]$$$listElementType -->
<h3 class="fn"><a name="listElementType"></a>const <span class="type"><a href="qmetaobject.html">QMetaObject</a></span> * QDeclarativeListReference::<span class="name">listElementType</span> () const</h3>
<p>Returns the <a href="qmetaobject.html">QMetaObject</a> for the elements stored in the list property. Returns 0 if the reference is invalid.</p>
<p>The <a href="qmetaobject.html">QMetaObject</a> can be used ahead of time to determine whether a given instance can be added to a list.</p>
<!-- @@@listElementType -->
<!-- $$$object[overload1]$$$object -->
<h3 class="fn"><a name="object"></a><span class="type"><a href="qobject.html">QObject</a></span> * QDeclarativeListReference::<span class="name">object</span> () const</h3>
<p>Returns the list property's object. Returns 0 if the reference is invalid.</p>
<!-- @@@object -->
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