StateMachine<_, Data> states don't have access to the type of Data

[danneu]

(Btw, I love this game engine. Thanks for all the work.)

Reference: src/engine/Util/StateMachine.ts

consider this state machine:

import { StateMachine, StateMachineDescription } from "excalibur";

type Data = { counter: number }

const data: Data = { counter: 0 };

const description: StateMachineDescription = {
  start: "Idle",
  states: {
    Idle: {
      transitions: [],
      onEnter: ({ data }) => { // data is `any`
        console.log("data is", data);
      },
    },
  },
};

const stateMachine: StateMachine<'Idle', Data> = StateMachine.create(description, { counter: 0 });

Since neither StateMachineDescription nor State have any type parameters, they can't know the Data parameter of the StateMachine that they're used in.

Instead I expected the types to be defined StateMachineDescription<States, Data> and State<Data> which would have to match StateMachine<States, Data> so that you can write type-safe states.

Aside, shouldn't there be a stateMachine.start(data) method to kick off the machine starting at startingState?

[eonarheim]

@danneu Thanks for the kind words, I tweaked the types on the main line branch to type the data as you expect. dccb762

For a start() method I'll need to think a little longer, but makes sense. Currently the machine is "implicitly" started when created.

[eonarheim]

@danneu this should be live now in the latest v0.30.x!