The QSignalSpy class enables introspection of signal emission. More...
#include <QSignalSpy>
Inherits: QObject and QList<QList<QVariant> >.
QSignalSpy ( QObject * object, const char * signal ) | |
bool | isValid () const |
QByteArray | signal () const |
The QSignalSpy class enables introspection of signal emission.
QSignalSpy can connect to any signal of any object and records its emission. QSignalSpy itself is a list of QVariant lists. Each emission of the signal will append one item to the list, containing the arguments of the signal.
The following example records all signal emissions for the clicked() signal of a QCheckBox:
QCheckBox *box = ...; QSignalSpy spy(box, SIGNAL(clicked(bool))); // do something that triggers the signal box->animateClick(); QCOMPARE(spy.count(), 1); // make sure the signal was emitted exactly one time QList<QVariant> arguments = spy.takeFirst(); // take the first signal QVERIFY(arguments.at(0).toBool() == true); // verify the first argument
spy.takeFirst() returns the arguments for the first emitted signal, as a list of QVariant objects. The clicked() signal has a single bool argument, which is stored as the first entry in the list of arguments.
The example below catches a signal from a custom object:
QSignalSpy spy(myCustomObject, SIGNAL(mySignal(int, QString, double))); myCustomObject->doSomething(); // trigger emission of the signal QList<QVariant> arguments = spy.takeFirst(); QVERIFY(arguments.at(0).type() == QVariant::Int); QVERIFY(arguments.at(1).type() == QVariant::QString); QVERIFY(arguments.at(2).type() == QVariant::double);
Note: Non-standard data types need to be registered, using the qRegisterMetaType() function, before you can create a QSignalSpy. For example:
qRegisterMetaType<QModelIndex>("QModelIndex"); QSignalSpy spy(&model, SIGNAL(whatever(QModelIndex)));
To retrieve the QModelIndex, you can use qvariant_cast:
// get the first argument from the first received signal: QModelIndex result = qvariant_cast<QModelIndex>(spy.at(0).at(0));
Constructs a new QSignalSpy that listens for emissions of the signal from the QObject object. Neither signal nor object can be null.
Example:
QSignalSpy spy(myPushButton, SIGNAL(clicked(bool)));
Returns true if the signal spy listens to a valid signal, otherwise false.
Returns the normalized signal the spy is currently listening to.
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