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);