How to add data to SignalTransition in StateMachine

Pavel Romankov

Hello.
I have state machine and transitions between states like this:

QStateMachine stateMachine;
MyState *state1 = new MyState();
MyState *state2 = new MyState();
MyState *state3 = new MyState();

stateMachine.addState(state1);
stateMachine.addState(state2);
stateMachine.addState(state3);

stateMachine.setChildMode(QState::ChildMode::ExclusiveStates);
stateMachine.setInitialState(state1);

state1->addTransition(state1, &MyState::transitionToState2Required, state2);
state1->addTransition(state1, &MyState::transitionToState3Required, state3);
state2->addTransition(state2, &MyState::transitionToState3Required, state3);

stateMachine.start();

Everything works well, but now i need to transfer some data between states. For example i can use:

MyState::transitionToState3Required(QVariant data);

How i can transfer this data from signal to target state?

Pl45m4

@Pavel-Romankov said in How to add data to SignalTransition in StateMachine:

How i can transfer this data from signal to target state?

You can use that signal like any other signal in Qt. Connect it to a slot / function in your MyState class, that will handle the data and emit / trigger the signal during your current state anytime you want with data as argument.

Pavel Romankov

in my example i have 3 states, so i need make something like:

connect(state1, &MyState::transitionToState2Required, state2, &MyState::onTransitionExecuted);
connect(state1, &MyState::transitionToState3Required, state3, &MyState::onTransitionExecuted);

connect(state2, &MyState::transitionToState1Required, state1, &MyState::onTransitionExecuted);
connect(state2, &MyState::transitionToState3Required, state3, &MyState::onTransitionExecuted);

connect(state3, &MyState::transitionToState1Required, state1, &MyState::onTransitionExecuted);
connect(state3, &MyState::transitionToState2Required, state2, &MyState::onTransitionExecuted);

but if i have about 10 states I'll need to create about 100 such connections. may be there is any general mechanism?

as i understand, if make like this:

connect(state1, &MyState::transitionToState2Required, state2, &MyState::beforeTransitionExecuted);
state1->addTransition(state1, &MyState::transitionToState2Required, state2);

slot beforeTransitionExecuted will called before transition and i can save data in target slot?

and if i make:

state1->addTransition(state1, &MyState::transitionToState2Required, state2);
connect(state1, &MyState::transitionToState2Required, state2, &MyState::onTransitionExecuted);

transition will be executed early and only then onTransitionExecuted will be called? so it's better to use first variant?