State

A state must be a MonoBehaviour and must implement the IState interface. A default implementation of this interface is available as the StateBehaviour class.

Enter/Exit

The enter and exit functions are Task based:

public class StateA : StateBehaviour {
    private void Awake() {
        // You have access to the Machine variable which is the StateMachine that is running this state
    }

    public override Task Enter() {
        // Do stuff on enter
        return base.Enter();
    }

    public override Task Exit() {
        // Do stuff on exit
        return base.Exit();
    }

    // TIP: The regular unity events are not called if you enable the sync options on the StateMachine component !
    private void Update() {
    }
}

Create your state

namespace MyProject {
    [AddComponentMenu("My project/FSM 1/Game state")]
    public class GameState : StateBehaviour {
        StateMachine _machine => (StateMachine) Machine;

        public override Task Enter() {
            DoSomething();
            return base.Enter();
        }

        async void DoSomething() {
            await new WaitForSeconds(2f);
            _machine.ChangeState<ScoreState>();
        }
    }
}