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<td >Qt 5.12</td><td ><a href="qttest-index.html">Qt Test</a></td><td ><a href="qttest-module.html">C++ Classes</a></td><td >QSignalSpy</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right"><a href="qttest-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="#details">Detailed Description</a></li>
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<h1 class="title">QSignalSpy Class</h1>
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<p>The <a href="qsignalspy.html">QSignalSpy</a> class enables introspection of signal emission. <a href="#details">More...</a></p>
<!-- @@@QSignalSpy -->
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<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QSignalSpy></span>
</td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += testlib</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Inherits:</td><td class="memItemRight bottomAlign"> <a href="../qtcore/qobject.html">QObject</a></td></tr></table></div><ul>
<li><a href="qsignalspy-members.html">List of all members, including inherited members</a></li>
<li><a href="qsignalspy-obsolete.html">Obsolete members</a></li>
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<a name="public-functions"></a>
<h2 id="public-functions">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>(const QObject *<i>object</i>, const char *<i>signal</i>)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qsignalspy.html#QSignalSpy-1">QSignalSpy</a></b>(const QObject *<i>object</i>, PointerToMemberFunction <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>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qsignalspy.html#wait">wait</a></b>(int <i>timeout</i> = 5000)</td></tr>
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<li class="fn">31 public functions inherited from <a href="../qtcore/qobject.html#public-functions">QObject</a></li>
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<h3>Additional Inherited Members</h3>
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<li class="fn">1 property inherited from <a href="../qtcore/qobject.html#properties">QObject</a></li>
<li class="fn">1 public slot inherited from <a href="../qtcore/qobject.html#public-slots">QObject</a></li>
<li class="fn">2 signals inherited from <a href="../qtcore/qobject.html#signals">QObject</a></li>
<li class="fn">9 static public members inherited from <a href="../qtcore/qobject.html#static-public-members">QObject</a></li>
<li class="fn">9 protected functions inherited from <a href="../qtcore/qobject.html#protected-functions">QObject</a></li>
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<a name="details"></a>
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<div class="descr">
<h2 id="details">Detailed Description</h2>
<p>The <a href="qsignalspy.html">QSignalSpy</a> class enables introspection of signal emission.</p>
<p><a href="qsignalspy.html">QSignalSpy</a> can connect to any signal of any object and records its emission. <a href="qsignalspy.html">QSignalSpy</a> itself is a list of <a href="../qtcore/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 <code>clicked()</code> signal of a <a href="../qtwidgets/qcheckbox.html">QCheckBox</a>:</p>
<pre class="cpp">
<span class="type"><a href="../qtwidgets/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"><a href="qsignalspy.html#QSignalSpy">QSignalSpy</a></span> spy(box<span class="operator">,</span> SIGNAL(clicked(bool)));
<span class="comment">// do something that triggers the signal</span>
box<span class="operator">-</span><span class="operator">></span>animateClick();
QCOMPARE(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="../qtcore/qlist.html">QList</a></span><span class="operator"><</span><span class="type"><a href="../qtcore/qvariant.html">QVariant</a></span><span class="operator">></span> arguments <span class="operator">=</span> spy<span class="operator">.</span>takeFirst(); <span class="comment">// take the first signal</span>
QVERIFY(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><code>spy.takeFirst()</code> returns the arguments for the first emitted signal, as a list of <a href="../qtcore/qvariant.html">QVariant</a> objects. The <code>clicked()</code> 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"><a href="qsignalspy.html#QSignalSpy">QSignalSpy</a></span> spy(myCustomObject<span class="operator">,</span> SIGNAL(mySignal(<span class="type">int</span><span class="operator">,</span><span class="type"><a href="../qtcore/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="../qtcore/qlist.html">QList</a></span><span class="operator"><</span><span class="type"><a href="../qtcore/qvariant.html">QVariant</a></span><span class="operator">></span> arguments <span class="operator">=</span> spy<span class="operator">.</span>takeFirst();
QVERIFY(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="../qtcore/qvariant.html">QVariant</a></span><span class="operator">::</span>Int);
QVERIFY(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="../qtcore/qvariant.html">QVariant</a></span><span class="operator">::</span>String);
QVERIFY(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="../qtcore/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="../qtcore/qmetatype.html#qRegisterMetaType-1">qRegisterMetaType</a>() function, before you can create a <a href="qsignalspy.html">QSignalSpy</a>. For example:</p>
<pre class="cpp">
<a href="../qtcore/qmetatype.html#qRegisterMetaType-1">qRegisterMetaType</a><span class="operator"><</span>SomeStruct<span class="operator">></span>();
<span class="type"><a href="qsignalspy.html#QSignalSpy">QSignalSpy</a></span> spy(<span class="operator">&</span>model<span class="operator">,</span> SIGNAL(whatever(SomeStruct)));
</pre>
<p>To retrieve the instance, you can use <a href="../qtcore/qvariant.html#qvariant_cast">qvariant_cast</a>:</p>
<pre class="cpp">
<span class="comment">// get the first argument from the first received signal:</span>
SomeStruct result <span class="operator">=</span> qvariant_cast<span class="operator"><</span>SomeStruct<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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<!-- @@@QSignalSpy -->
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QSignalSpy[overload1]$$$QSignalSpyconstQObject*constchar* -->
<h3 class="fn" id="QSignalSpy"><a name="QSignalSpy"></a>QSignalSpy::<span class="name">QSignalSpy</span>(const <span class="type"><a href="../qtcore/qobject.html#QObject">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="../qtcore/qobject.html">QObject</a> <i>object</i>. If <a href="qsignalspy.html">QSignalSpy</a> is not able to listen for a valid signal (for example, because <i>object</i> is null or <i>signal</i> does not denote a valid signal of <i>object</i>), an explanatory warning message will be output using <a href="../qtcore/qtglobal.html#qWarning">qWarning</a>() and subsequent calls to <code>isValid()</code> will return false.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type">QSignalSpy</span> spy(myPushButton<span class="operator">,</span> SIGNAL(clicked(bool)));
</pre>
<!-- @@@QSignalSpy -->
<!-- $$$QSignalSpy$$$QSignalSpyconstQObject*PointerToMemberFunction -->
<h3 class="fn" id="QSignalSpy-1"><a name="QSignalSpy-1"></a>QSignalSpy::<span class="name">QSignalSpy</span>(const <span class="type"><a href="../qtcore/qobject.html#QObject">QObject</a></span> *<i>object</i>, <span class="type">PointerToMemberFunction</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="../qtcore/qobject.html">QObject</a> <i>object</i>. If <a href="qsignalspy.html">QSignalSpy</a> is not able to listen for a valid signal (for example, because <i>object</i> is null or <i>signal</i> does not denote a valid signal of <i>object</i>), an explanatory warning message will be output using <a href="../qtcore/qtglobal.html#qWarning">qWarning</a>() and subsequent calls to <code>isValid()</code> will return false.</p>
<p>Example:</p>
<pre class="cpp">
<span class="type"><a href="qsignalspy.html#QSignalSpy">QSignalSpy</a></span> spy(myPushButton<span class="operator">,</span> <span class="operator">&</span><span class="type"><a href="../qtwidgets/qpushbutton.html">QPushButton</a></span><span class="operator">::</span>clicked);
</pre>
<p>This function was introduced in Qt 5.4.</p>
<!-- @@@QSignalSpy -->
<!-- $$$isValid[overload1]$$$isValid -->
<h3 class="fn" id="isValid"><a name="isValid"></a><span class="type">bool</span> QSignalSpy::<span class="name">isValid</span>() const</h3>
<p>Returns <code>true</code> if the signal spy listens to a valid signal, otherwise false.</p>
<!-- @@@isValid -->
<!-- $$$signal[overload1]$$$signal -->
<h3 class="fn" id="signal"><a name="signal"></a><span class="type"><a href="../qtcore/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 -->
<!-- $$$wait[overload1]$$$waitint -->
<h3 class="fn" id="wait"><a name="wait"></a><span class="type">bool</span> QSignalSpy::<span class="name">wait</span>(<span class="type">int</span> <i>timeout</i> = 5000)</h3>
<p>Starts an event loop that runs until the given signal is received. Optionally the event loop can return earlier on a <i>timeout</i> (in milliseconds).</p>
<p>Returns <code>true</code> if the signal was emitted at least once in <i>timeout</i> milliseconds, otherwise returns <code>false</code>.</p>
<p>Example:</p>
<pre class="cpp">
QVERIFY(spy<span class="operator">.</span>wait(<span class="number">1000</span>));
</pre>
<p>This function was introduced in Qt 5.0.</p>
<!-- @@@wait -->
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