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# QSignalTransition Class Reference
[QtCore module]

The QSignalTransition class provides a transition based on a Qt signal. More...

Inherits QAbstractTransition.

### Methods

- __init__ (self, QState sourceState = None)
- __init__ (self, QObject sender, SIGNAL() signal, QState sourceState = None)
- __init__ (self, signal signal, QState sourceState = None)
- bool event (self, QEvent e)
- bool eventTest (self, QEvent event)
- onTransition (self, QEvent event)
- QObject senderObject (self)
- setSenderObject (self, QObject sender)
- setSignal (self, QByteArray signal)
- QByteArray signal (self)

## Detailed Description

The QSignalTransition class provides a transition based on a Qt signal.

Typically you would use the overload of QState.addTransition() that takes a sender and signal as arguments, rather than creating QSignalTransition objects directly. QSignalTransition is part of The State Machine Framework.

You can subclass QSignalTransition and reimplement eventTest() to make a signal transition conditional; the event object passed to eventTest() will be a QStateMachine.SignalEvent object. Example:

     class CheckedTransition : public QSignalTransition
     {
     public:
         CheckedTransition(QCheckBox *check)
             : QSignalTransition(check, SIGNAL(stateChanged(int))) {}
     protected:
         bool eventTest(QEvent *e) {
             if (!QSignalTransition.eventTest(e))
                 return false;
             QStateMachine.SignalEvent *se = static_cast<QStateMachine.SignalEvent*>(e);
             return (se->arguments().at(0).toInt() == Qt.Checked);
         }
     };

     ...

     QCheckBox *check = new QCheckBox();
     check->setTristate(true);

     QState *s1 = new QState();
     QState *s2 = new QState();
     CheckedTransition *t1 = new CheckedTransition(check);
     t1->setTargetState(s2);
     s1->addTransition(t1);

## Method Documentation

### QSignalTransition.__init__ (self, QState sourceState = None)

Constructs a new signal transition with the given sourceState.

### QSignalTransition.__init__ (self, QObject sender, SIGNAL() signal, QState sourceState = None)

Constructs a new signal transition associated with the given signal of the given sender, and with the given sourceState.

### QSignalTransition.__init__ (self, signal signal, QState sourceState = None)

### bool QSignalTransition.event (self, QEvent e)

Reimplemented from QObject.event().

### bool QSignalTransition.eventTest (self, QEvent event)

Reimplemented from QAbstractTransition.eventTest().

The default implementation returns true if the event is a QStateMachine.SignalEvent object and the event's sender and signal index match this transition, and returns false otherwise.

### QSignalTransition.onTransition (self, QEvent event)

Reimplemented from QAbstractTransition.onTransition().

### QObject QSignalTransition.senderObject (self)

### QSignalTransition.setSenderObject (self, QObject sender)

### QSignalTransition.setSignal (self, QByteArray signal)

### QByteArray QSignalTransition.signal (self)