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| -rw-r--r-- | doc/src/frameworks-technologies/statemachine.qdoc | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/doc/src/frameworks-technologies/statemachine.qdoc b/doc/src/frameworks-technologies/statemachine.qdoc index 2b137dd..ed8bc85 100644 --- a/doc/src/frameworks-technologies/statemachine.qdoc +++ b/doc/src/frameworks-technologies/statemachine.qdoc @@ -304,6 +304,35 @@ For parallel state groups, the QState::finished() signal is emitted when \e all the child states have entered final states. + \section1 Targetless Transitions + + A transition need not have a target state. A transition without a target can + be triggered the same way as any other transition; the difference is that + when a targetless transition is triggered, it doesn't cause any state + changes. This allows you to react to a signal or event when your machine is + in a certain state, without having to leave that state. Example: + + \code + QStateMachine machine; + QState *s1 = new QState(&machine); + + QPushButton button; + QSignalTransition *trans = new QSignalTransition(&button, SIGNAL(clicked())); + s1->addTransition(trans); + + QMessageBox msgBox; + msgBox.setText("The button was clicked; carry on."); + QObject::connect(trans, SIGNAL(triggered()), &msgBox, SLOT(exec())); + + machine.setInitialState(s1); + \endcode + + The message box will be displayed each time the button is clicked, but the + state machine will remain in its current state (s1). If the target state + were explicitly set to s1, however, s1 would be exited and re-entered each + time (e.g. the QAbstractState::entered() and QAbstractState::exited() + signals would be emitted). + \section1 Events, Transitions and Guards A QStateMachine runs its own event loop. For signal transitions |