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<td >Qt 5.12</td><td ><a href="qtqml-index.html">Qt QML</a></td><td ><a href="qtqml-module.html">C++ Classes</a></td><td >QQmlPropertyMap</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right"><a href="qtqml-index.html">Qt 5.12.6 Reference Documentation</a></td>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#signals">Signals</a></li>
<li class="level1"><a href="#static-public-members">Static Public Members</a></li>
<li class="level1"><a href="#protected-functions">Protected Functions</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
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<h1 class="title">QQmlPropertyMap Class</h1>
<!-- $$$QQmlPropertyMap-brief -->
<p>The <a href="qqmlpropertymap.html">QQmlPropertyMap</a> class allows you to set key-value pairs that can be used in QML bindings. <a href="#details">More...</a></p>
<!-- @@@QQmlPropertyMap -->
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QQmlPropertyMap></span>
</td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += qml</td></tr></table></div><ul>
<li><a href="qqmlpropertymap-members.html">List of all members, including inherited members</a></li>
</ul>
<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="qqmlpropertymap.html#QQmlPropertyMap">QQmlPropertyMap</a></b>(QObject *<i>parent</i> = nullptr)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#dtor.QQmlPropertyMap">~QQmlPropertyMap</a></b>() override</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#clear">clear</a></b>(const QString &<i>key</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#contains">contains</a></b>(const QString &<i>key</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#count">count</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#insert">insert</a></b>(const QString &<i>key</i>, const QVariant &<i>value</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#isEmpty">isEmpty</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QStringList </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#keys">keys</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> int </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#size">size</a></b>() const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QVariant </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#value">value</a></b>(const QString &<i>key</i>) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QVariant &</td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#operator-5b-5d">operator[]</a></b>(const QString &<i>key</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QVariant </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#operator-5b-5d-1">operator[]</a></b>(const QString &<i>key</i>) const</td></tr>
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<a name="signals"></a>
<h2 id="signals">Signals</h2>
<div class="table"><table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#valueChanged">valueChanged</a></b>(const QString &<i>key</i>, const QVariant &<i>value</i>)</td></tr>
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<a name="static-public-members"></a>
<h2 id="static-public-members">Static Public Members</h2>
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<tr><td class="memItemLeft rightAlign topAlign"> const QMetaObject </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#staticMetaObject-var">staticMetaObject</a></b></td></tr>
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<a name="protected-functions"></a>
<h2 id="protected-functions">Protected Functions</h2>
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<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#QQmlPropertyMap-1">QQmlPropertyMap</a></b>(DerivedType *<i>derived</i>, QObject *<i>parent</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual QVariant </td><td class="memItemRight bottomAlign"><b><a href="qqmlpropertymap.html#updateValue">updateValue</a></b>(const QString &<i>key</i>, const QVariant &<i>input</i>)</td></tr>
</table></div>
<a name="details"></a>
<!-- $$$QQmlPropertyMap-description -->
<div class="descr">
<h2 id="details">Detailed Description</h2>
<p>The <a href="qqmlpropertymap.html">QQmlPropertyMap</a> class allows you to set key-value pairs that can be used in QML bindings.</p>
<p><a href="qqmlpropertymap.html">QQmlPropertyMap</a> provides a convenient way to expose domain data to the UI layer. The following example shows how you might declare data in C++ and then access it in QML.</p>
<p>In the C++ file:</p>
<pre class="cpp">
<span class="comment">// create our data</span>
<span class="type"><a href="qqmlpropertymap.html#QQmlPropertyMap">QQmlPropertyMap</a></span> ownerData;
ownerData<span class="operator">.</span>insert(<span class="string">"name"</span><span class="operator">,</span> <span class="type">QVariant</span>(<span class="type">QString</span>(<span class="string">"John Smith"</span>)));
ownerData<span class="operator">.</span>insert(<span class="string">"phone"</span><span class="operator">,</span> <span class="type">QVariant</span>(<span class="type">QString</span>(<span class="string">"555-5555"</span>)));
<span class="comment">// expose it to the UI layer</span>
<span class="type">QQuickView</span> view;
<span class="type"><a href="qqmlcontext.html">QQmlContext</a></span> <span class="operator">*</span>ctxt <span class="operator">=</span> view<span class="operator">.</span>rootContext();
ctxt<span class="operator">-</span><span class="operator">></span>setContextProperty(<span class="string">"owner"</span><span class="operator">,</span> <span class="operator">&</span>ownerData);
view<span class="operator">.</span>setSource(<span class="type">QUrl</span><span class="operator">::</span>fromLocalFile(<span class="string">"main.qml"</span>));
view<span class="operator">.</span>show();
</pre>
<p>Then, in <code>main.qml</code>:</p>
<pre class="cpp">
Text { text: owner<span class="operator">.</span>name <span class="operator">+</span> <span class="string">" "</span> <span class="operator">+</span> owner<span class="operator">.</span>phone }
</pre>
<p>The binding is dynamic - whenever a key's value is updated, anything bound to that key will be updated as well.</p>
<p>To detect value changes made in the UI layer you can connect to the <a href="qqmlpropertymap.html#valueChanged">valueChanged</a>() signal. However, note that <a href="qqmlpropertymap.html#valueChanged">valueChanged</a>() is <b>NOT</b> emitted when changes are made by calling <a href="qqmlpropertymap.html#insert">insert</a>() or <a href="qqmlpropertymap.html#clear">clear</a>() - it is only emitted when a value is updated from QML.</p>
<p><b>Note: </b>It is not possible to remove keys from the map; once a key has been added, you can only modify or clear its associated value.</p><p><b>Note: </b>When deriving a class from <a href="qqmlpropertymap.html">QQmlPropertyMap</a>, use the <a href="qqmlpropertymap.html#QQmlPropertyMap-1">protected two-argument constructor</a> which ensures that the class is correctly registered with the Qt Meta-Object System.</p><p><b>Note: </b>The QMetaObject of a <a href="qqmlpropertymap.html">QQmlPropertyMap</a> is dynamically generated and modified. Operations on that meta object are not thread safe, so applications need to take care to explicitly synchronize access to the meta object.</p></div>
<!-- @@@QQmlPropertyMap -->
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QQmlPropertyMap[overload1]$$$QQmlPropertyMapQObject* -->
<h3 class="fn" id="QQmlPropertyMap"><a name="QQmlPropertyMap"></a>QQmlPropertyMap::<span class="name">QQmlPropertyMap</span>(<span class="type">QObject</span> *<i>parent</i> = nullptr)</h3>
<p>Constructs a bindable map with parent object <i>parent</i>.</p>
<!-- @@@QQmlPropertyMap -->
<!-- $$$QQmlPropertyMap$$$QQmlPropertyMapDerivedType*QObject* -->
<h3 class="fn" id="QQmlPropertyMap-1"><a name="QQmlPropertyMap-1"></a><code>[protected] </code>QQmlPropertyMap::<span class="name">QQmlPropertyMap</span>(<span class="type">DerivedType</span> *<i>derived</i>, <span class="type">QObject</span> *<i>parent</i>)</h3>
<p>Constructs a bindable map with parent object <i>parent</i>. Use this constructor in classes derived from <a href="qqmlpropertymap.html">QQmlPropertyMap</a>.</p>
<p>The type of <i>derived</i> is used to register the property map with the Meta-Object System, which is necessary to ensure that properties of the derived class are accessible. This type must be derived from <a href="qqmlpropertymap.html">QQmlPropertyMap</a>.</p>
<!-- @@@QQmlPropertyMap -->
<!-- $$$~QQmlPropertyMap[overload1]$$$~QQmlPropertyMap -->
<h3 class="fn" id="dtor.QQmlPropertyMap"><a name="dtor.QQmlPropertyMap"></a><code>[override virtual] </code>QQmlPropertyMap::<span class="name">~QQmlPropertyMap</span>()</h3>
<p>Destroys the bindable map.</p>
<!-- @@@~QQmlPropertyMap -->
<!-- $$$clear[overload1]$$$clearconstQString& -->
<h3 class="fn" id="clear"><a name="clear"></a><span class="type">void</span> QQmlPropertyMap::<span class="name">clear</span>(const <span class="type">QString</span> &<i>key</i>)</h3>
<p>Clears the value (if any) associated with <i>key</i>.</p>
<!-- @@@clear -->
<!-- $$$contains[overload1]$$$containsconstQString& -->
<h3 class="fn" id="contains"><a name="contains"></a><span class="type">bool</span> QQmlPropertyMap::<span class="name">contains</span>(const <span class="type">QString</span> &<i>key</i>) const</h3>
<p>Returns true if the map contains <i>key</i>.</p>
<p><b>See also </b><a href="qqmlpropertymap.html#size">size</a>().</p>
<!-- @@@contains -->
<!-- $$$count[overload1]$$$count -->
<h3 class="fn" id="count"><a name="count"></a><span class="type">int</span> QQmlPropertyMap::<span class="name">count</span>() const</h3>
<p>This is an overloaded function.</p>
<p>Same as <a href="qqmlpropertymap.html#size">size</a>().</p>
<!-- @@@count -->
<!-- $$$insert[overload1]$$$insertconstQString&constQVariant& -->
<h3 class="fn" id="insert"><a name="insert"></a><span class="type">void</span> QQmlPropertyMap::<span class="name">insert</span>(const <span class="type">QString</span> &<i>key</i>, const <span class="type">QVariant</span> &<i>value</i>)</h3>
<p>Sets the value associated with <i>key</i> to <i>value</i>.</p>
<p>If the key doesn't exist, it is automatically created.</p>
<!-- @@@insert -->
<!-- $$$isEmpty[overload1]$$$isEmpty -->
<h3 class="fn" id="isEmpty"><a name="isEmpty"></a><span class="type">bool</span> QQmlPropertyMap::<span class="name">isEmpty</span>() const</h3>
<p>Returns true if the map contains no keys; otherwise returns false.</p>
<p><b>See also </b><a href="qqmlpropertymap.html#size">size</a>().</p>
<!-- @@@isEmpty -->
<!-- $$$keys[overload1]$$$keys -->
<h3 class="fn" id="keys"><a name="keys"></a><span class="type">QStringList</span> QQmlPropertyMap::<span class="name">keys</span>() const</h3>
<p>Returns the list of keys.</p>
<p>Keys that have been cleared will still appear in this list, even though their associated values are invalid QVariants.</p>
<p><b>Note: </b>This function can be invoked via the meta-object system and from QML. See Q_INVOKABLE.</p>
<!-- @@@keys -->
<!-- $$$size[overload1]$$$size -->
<h3 class="fn" id="size"><a name="size"></a><span class="type">int</span> QQmlPropertyMap::<span class="name">size</span>() const</h3>
<p>Returns the number of keys in the map.</p>
<p><b>See also </b><a href="qqmlpropertymap.html#isEmpty">isEmpty</a>() and <a href="qqmlpropertymap.html#count">count</a>().</p>
<!-- @@@size -->
<!-- $$$updateValue[overload1]$$$updateValueconstQString&constQVariant& -->
<h3 class="fn" id="updateValue"><a name="updateValue"></a><code>[virtual protected] </code><span class="type">QVariant</span> QQmlPropertyMap::<span class="name">updateValue</span>(const <span class="type">QString</span> &<i>key</i>, const <span class="type">QVariant</span> &<i>input</i>)</h3>
<p>Returns the new value to be stored for the key <i>key</i>. This function is provided to intercept updates to a property from QML, where the value provided from QML is <i>input</i>.</p>
<p>Override this function to manipulate the property value as it is updated. Note that this function is only invoked when the value is updated from QML.</p>
<!-- @@@updateValue -->
<!-- $$$value[overload1]$$$valueconstQString& -->
<h3 class="fn" id="value"><a name="value"></a><span class="type">QVariant</span> QQmlPropertyMap::<span class="name">value</span>(const <span class="type">QString</span> &<i>key</i>) const</h3>
<p>Returns the value associated with <i>key</i>.</p>
<p>If no value has been set for this key (or if the value has been cleared), an invalid QVariant is returned.</p>
<!-- @@@value -->
<!-- $$$valueChanged[overload1]$$$valueChangedconstQString&constQVariant& -->
<h3 class="fn" id="valueChanged"><a name="valueChanged"></a><code>[signal] </code><span class="type">void</span> QQmlPropertyMap::<span class="name">valueChanged</span>(const <span class="type">QString</span> &<i>key</i>, const <span class="type">QVariant</span> &<i>value</i>)</h3>
<p>This signal is emitted whenever one of the values in the map is changed. <i>key</i> is the key corresponding to the <i>value</i> that was changed.</p>
<p><b>Note: </b>valueChanged() is <b>NOT</b> emitted when changes are made by calling <a href="qqmlpropertymap.html#insert">insert</a>() or <a href="qqmlpropertymap.html#clear">clear</a>() - it is only emitted when a value is updated from QML.</p><!-- @@@valueChanged -->
<!-- $$$operator[][overload1]$$$operator[]constQString& -->
<h3 class="fn" id="operator-5b-5d"><a name="operator-5b-5d"></a><span class="type">QVariant</span> &QQmlPropertyMap::<span class="name">operator[]</span>(const <span class="type">QString</span> &<i>key</i>)</h3>
<p>Returns the value associated with the key <i>key</i> as a modifiable reference.</p>
<p>If the map contains no item with key <i>key</i>, the function inserts an invalid QVariant into the map with key <i>key</i>, and returns a reference to it.</p>
<p><b>See also </b><a href="qqmlpropertymap.html#insert">insert</a>() and <a href="qqmlpropertymap.html#value">value</a>().</p>
<!-- @@@operator[] -->
<!-- $$$operator[]$$$operator[]constQString& -->
<h3 class="fn" id="operator-5b-5d-1"><a name="operator-5b-5d-1"></a><span class="type">QVariant</span> QQmlPropertyMap::<span class="name">operator[]</span>(const <span class="type">QString</span> &<i>key</i>) const</h3>
<p>This is an overloaded function.</p>
<p>Same as <a href="qqmlpropertymap.html#value">value</a>().</p>
<!-- @@@operator[] -->
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