How to implement the publish-subscribe pattern in TypeScript?

I'm working on creating an events system for my game, and my code currently looks like this:

export const enum ET { Collision, Dying, Damage }

type ActionCallback = (scene: Scene, event: GameEvent) => void;

subscribe(eventType: ET, callback: ActionCallback) {
  this.subscriptions[eventType].push(callback);
}

And then an example of some code which uses this function is like this:

scene.events.subscribe(ET.Dying, handleEntityDeath);

handleEntityDeath = (scene: Scene, event: DyingEvent) => {
  scene.deleteEntity(event.entity);
}

The problem is that TypeScript fails to compile and says something like: event's type must be GameEvent and not DyingEvent.

Basically, I need a way to "link" ET.Dying and DyingEvent, but I'm not sure how to do it. I think if I can accomplish this, then I can event handlers like the above where it will only compile if the first parameter is something like ET.Dying and the second parameter is a callback which takes a DyingEvent. I would want it to fail to compile if the callback instead had a DamageEvent parameter, if that makes sense.

Can this be done, and if so, how?


Figured it out:

interface EventMap {
  [ET.Collision]: CollisionEvent;
  [ET.Dying]: DyingEvent;
  // etc
}

subscribe = <T extends ET>(eventType: T, callback: (scene: Scene, event: EventMap[T]) => void) => {
  this.subscriptions[eventType].push(callback);
}

// Example calling code below here:

scene.events.subscribe(ET.Dying, handleEntityDeath);

handleEntityDeath = (scene: Scene, event: DyingEvent) => {
  scene.deleteEntity(event.entity);
}