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<a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
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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="#details">Detailed Description</a></li>
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<h1 class="title">QSignalSpy Class Reference</h1>
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<p>The QSignalSpy class enables introspection of signal emission. <a href="#details">More...</a></p>
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<pre class="cpp"> <span class="preprocessor">#include <QSignalSpy></span></pre><p><b>Inherits: </b><a href="qobject.html">QObject</a> and <a href="qlist.html">QList<QList<QVariant> ></a>.</p>
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<li><a href="qsignalspy-members.html">List of all members, including inherited members</a></li>
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<a name="public-functions"></a>
<h2>Public Functions</h2>
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<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qsignalspy.html#QSignalSpy">QSignalSpy</a></b> ( QObject * <i>object</i>, const char * <i>signal</i> )</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qsignalspy.html#isValid">isValid</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QByteArray </td><td class="memItemRight bottomAlign"><b><a href="qsignalspy.html#signal">signal</a></b> () const</td></tr>
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<li class="fn">29 public functions inherited from <a href="qobject.html#public-functions">QObject</a></li>
<li class="fn">67 public functions inherited from <a href="qlist.html#public-functions">QList</a></li>
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<h3>Additional Inherited Members</h3>
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<li class="fn">1 property inherited from <a href="qobject.html#properties">QObject</a></li>
<li class="fn">1 public slot inherited from <a href="qobject.html#public-slots">QObject</a></li>
<li class="fn">1 signal inherited from <a href="qobject.html#signals">QObject</a></li>
<li class="fn">7 static public members inherited from <a href="qobject.html#static-public-members">QObject</a></li>
<li class="fn">3 static public members inherited from <a href="qlist.html#static-public-members">QList</a></li>
<li class="fn">8 protected functions inherited from <a href="qobject.html#protected-functions">QObject</a></li>
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<h2>Detailed Description</h2>
<p>The QSignalSpy class enables introspection of signal emission.</p>
<p>QSignalSpy can connect to any signal of any object and records its emission. QSignalSpy itself is a list of <a href="qvariant.html">QVariant</a> lists. Each emission of the signal will append one item to the list, containing the arguments of the signal.</p>
<p>The following example records all signal emissions for the <tt>clicked()</tt> signal of a <a href="qcheckbox.html">QCheckBox</a>:</p>
<pre class="cpp"> <span class="type"><a href="qcheckbox.html">QCheckBox</a></span> <span class="operator">*</span>box <span class="operator">=</span> <span class="operator">.</span><span class="operator">.</span><span class="operator">.</span>;
<span class="type">QSignalSpy</span> spy(box<span class="operator">,</span> SIGNAL(clicked(<span class="type">bool</span>)));
<span class="comment">// do something that triggers the signal</span>
box<span class="operator">-</span><span class="operator">></span>animateClick();
<a href="qtest.html#QCOMPARE">QCOMPARE</a>(spy<span class="operator">.</span>count()<span class="operator">,</span> <span class="number">1</span>); <span class="comment">// make sure the signal was emitted exactly one time</span>
<span class="type"><a href="qlist.html">QList</a></span><span class="operator"><</span><span class="type"><a href="qvariant.html">QVariant</a></span><span class="operator">></span> arguments <span class="operator">=</span> spy<span class="operator">.</span><a href="qlist.html#takeFirst">takeFirst</a>(); <span class="comment">// take the first signal</span>
<a href="qtest.html#QVERIFY">QVERIFY</a>(arguments<span class="operator">.</span>at(<span class="number">0</span>)<span class="operator">.</span>toBool() <span class="operator">=</span><span class="operator">=</span> <span class="keyword">true</span>); <span class="comment">// verify the first argument</span></pre>
<p><tt>spy.takeFirst()</tt> returns the arguments for the first emitted signal, as a list of <a href="qvariant.html">QVariant</a> objects. The <tt>clicked()</tt> signal has a single bool argument, which is stored as the first entry in the list of arguments.</p>
<p>The example below catches a signal from a custom object:</p>
<pre class="cpp"> <span class="type">QSignalSpy</span> spy(myCustomObject<span class="operator">,</span> SIGNAL(mySignal(<span class="type">int</span><span class="operator">,</span> <span class="type"><a href="qstring.html">QString</a></span><span class="operator">,</span> <span class="type">double</span>)));
myCustomObject<span class="operator">-</span><span class="operator">></span>doSomething(); <span class="comment">// trigger emission of the signal</span>
<span class="type"><a href="qlist.html">QList</a></span><span class="operator"><</span><span class="type"><a href="qvariant.html">QVariant</a></span><span class="operator">></span> arguments <span class="operator">=</span> spy<span class="operator">.</span><a href="qlist.html#takeFirst">takeFirst</a>();
<a href="qtest.html#QVERIFY">QVERIFY</a>(arguments<span class="operator">.</span>at(<span class="number">0</span>)<span class="operator">.</span>type() <span class="operator">=</span><span class="operator">=</span> <span class="type"><a href="qvariant.html">QVariant</a></span><span class="operator">::</span>Int);
<a href="qtest.html#QVERIFY">QVERIFY</a>(arguments<span class="operator">.</span>at(<span class="number">1</span>)<span class="operator">.</span>type() <span class="operator">=</span><span class="operator">=</span> <span class="type"><a href="qvariant.html">QVariant</a></span><span class="operator">::</span><span class="type"><a href="qstring.html">QString</a></span>);
<a href="qtest.html#QVERIFY">QVERIFY</a>(arguments<span class="operator">.</span>at(<span class="number">2</span>)<span class="operator">.</span>type() <span class="operator">=</span><span class="operator">=</span> <span class="type"><a href="qvariant.html">QVariant</a></span><span class="operator">::</span><span class="type">double</span>);</pre>
<p><b>Note:</b> Non-standard data types need to be registered, using the <a href="qmetatype.html#qRegisterMetaType">qRegisterMetaType</a>() function, before you can create a QSignalSpy. For example:</p>
<pre class="cpp"> <a href="qmetatype.html#qRegisterMetaType">qRegisterMetaType</a><span class="operator"><</span><span class="type"><a href="qmodelindex.html">QModelIndex</a></span><span class="operator">></span>(<span class="string">"QModelIndex"</span>);
<span class="type">QSignalSpy</span> spy(<span class="operator">&</span>model<span class="operator">,</span> SIGNAL(whatever(<span class="type"><a href="qmodelindex.html">QModelIndex</a></span>)));</pre>
<p>To retrieve the <tt>QModelIndex</tt>, you can use qvariant_cast:</p>
<pre class="cpp"> <span class="comment">// get the first argument from the first received signal:</span>
<span class="type"><a href="qmodelindex.html">QModelIndex</a></span> result <span class="operator">=</span> qvariant_cast<span class="operator"><</span><span class="type"><a href="qmodelindex.html">QModelIndex</a></span><span class="operator">></span>(spy<span class="operator">.</span>at(<span class="number">0</span>)<span class="operator">.</span>at(<span class="number">0</span>));</pre>
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<div class="func">
<h2>Member Function Documentation</h2>
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<h3 class="fn"><a name="QSignalSpy"></a>QSignalSpy::<span class="name">QSignalSpy</span> ( <span class="type"><a href="qobject.html">QObject</a></span> * <i>object</i>, const <span class="type">char</span> * <i>signal</i> )</h3>
<p>Constructs a new <a href="qsignalspy.html">QSignalSpy</a> that listens for emissions of the <i>signal</i> from the <a href="qobject.html">QObject</a> <i>object</i>. Neither <i>signal</i> nor <i>object</i> can be null.</p>
<p>Example:</p>
<pre class="cpp"> <span class="type"><a href="qsignalspy.html">QSignalSpy</a></span> spy(myPushButton<span class="operator">,</span> SIGNAL(clicked(<span class="type">bool</span>)));</pre>
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<h3 class="fn"><a name="isValid"></a><span class="type">bool</span> QSignalSpy::<span class="name">isValid</span> () const</h3>
<p>Returns true if the signal spy listens to a valid signal, otherwise false.</p>
<!-- @@@isValid -->
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<h3 class="fn"><a name="signal"></a><span class="type"><a href="qbytearray.html">QByteArray</a></span> QSignalSpy::<span class="name">signal</span> () const</h3>
<p>Returns the normalized signal the spy is currently listening to.</p>
<!-- @@@signal -->
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