state_composer 0.0.0

Create ComposerState machines with object composition

State Composer

Create state machines in dart using object composition
This package is under development. For now only suports simple transitions between states. Next steps are add listeners and parallel states

Usage

A simple machine with to states

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"),
      ],
    )
  ],
);

Transitioning between states

print(machine.currentState!.id) //A
await machine.transitionTo("B");
//Leaving A
//Leaving A future completed
//Entered B
print(machine.currentState!.id) //B

Generic State and Transition Types

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

Listening to State Changes

Use the state machines' stateStream to listen the state changes

machine.stateStream.listen((currentState) {
  print("State Changed to ${currentState.id}");
});