Create state machines in dart using object composition
Next steps are to add parallel states and transition guards
Instanciate your StateMachine passing its id, i.e. a unique name, the inintial state id and a list of states
Each ComposerState also have an id that can really be whatever you want to call it, as long as there is no other state with this name
States execute stuff through onEnter and onLeave functions.
onEnter will pass the last and current states
onLeave will pass the current and next states
Ps: those functions accept futures
All transitions that a state is allowed to make must be inside the transitions list. A Transition also receives an id,
and the id of the state that you want to go to
machine = StateMachine(
id: "machine1",
initialStateId: "A",
states: [
ComposerState(
id: "A",
onEnter: (stateMachine) async {
test("onEnter A Last State Should be Null", () {
expect(stateMachine.lastState, null);
});
test("onEnter A Current State ID Should be A", () {
expect(stateMachine.currentState!.id, "A");
});
print("Entered A");
},
onLeave: (stateMachine, nextState) async {
print("Leaving A");
expect(stateMachine.currentState!.id, "A");
expect(nextState.id, "B");
await Future.delayed(Duration(seconds: 3));
print("Leaving A future completed");
},
transitions: [
Transition(id: "A=>B", to: "B"),
],
),
ComposerState(
id: "B",
onEnter: (stateMachine) {
print("Entered B");
expect(stateMachine.lastState!.id, "A");
expect(stateMachine.currentState!.id, "B");
},
onLeave: (currentState, nextState) {
print("leaving B");
expect(currentState.id, "B");
expect(nextState.id, "A");
},
transitions: [
Transition(id: "B=>A", to: "A"),
],
)
],
);
print(machine.currentState!.id) //A
await machine.transitionTo("B");
//Leaving A
//Leaving A future completed
//Entered B
print(machine.currentState!.id) //B
You can create personalized states and transitions that extends ComposerState and Transition. To see an
example look at flutter_chat_composer’s model
that extends state_composer to create a chatbot based on state machines
Use the state machines’ stateStream to listen the state changes
machine.stateStream.listen((currentState) {
print("State Changed to ${currentState.id}");
});
https://github.com/FelipeMarra/state_composer
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