<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html lang="en"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <!-- qsignalspy.qdoc --> <title>QSignalSpy Class | Qt Test 5.12.6</title> <link rel="stylesheet" type="text/css" href="style/offline-simple.css" /> <script type="text/javascript"> document.getElementsByTagName("link").item(0).setAttribute("href", "style/offline.css"); // loading style sheet breaks anchors that were jumped to before // so force jumping to anchor again setTimeout(function() { var anchor = location.hash; // need to jump to different anchor first (e.g. none) location.hash = "#"; setTimeout(function() { location.hash = anchor; }, 0); }, 0); </script> </head> <body> <div class="header" id="qtdocheader"> <div class="main"> <div class="main-rounded"> <div class="navigationbar"> <table><tr> <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> </tr></table> </div> </div> <div class="content"> <div class="line"> <div class="content mainContent"> <div class="sidebar"> <div class="toc"> <h3><a name="toc">Contents</a></h3> <ul> <li class="level1"><a href="#public-functions">Public Functions</a></li> <li class="level1"><a href="#details">Detailed Description</a></li> </ul> </div> <div class="sidebar-content" id="sidebar-content"></div></div> <h1 class="title">QSignalSpy Class</h1> <!-- $$$QSignalSpy-brief --> <p>The <a href="qsignalspy.html">QSignalSpy</a> class enables introspection of signal emission. <a href="#details">More...</a></p> <!-- @@@QSignalSpy --> <div class="table"><table class="alignedsummary"> <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> </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="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> </table></div> <ul> <li class="fn">31 public functions inherited from <a href="../qtcore/qobject.html#public-functions">QObject</a></li> </ul> <h3>Additional Inherited Members</h3> <ul> <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> </ul> <a name="details"></a> <!-- $$$QSignalSpy-description --> <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> </div> <!-- @@@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 --> </div> </div> </div> </div> </div> </div> <div class="footer"> <p> <acronym title="Copyright">©</acronym> 2019 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners.<br/> The documentation provided herein is licensed under the terms of the <a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation License version 1.3</a> as published by the Free Software Foundation.<br/> Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. 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