hasparus · May 20, 2019 08:03 · hasparus · May 20, 2019
diff --git a/ecs.ts b/ecs.ts
 // components.ts
 type Component = Components[keyof Components]; // Health | Transform

 interface Components { /* add new components to this interface in separate files */ }

 // health.ts
 type Health = number & { __brand: 'Health' };

 interface Components {
    health: Health; 
 }

 // transform.ts
 class Transform { };

 interface Components {
    transform: Transform;
 }

 // entity.ts
 type Entity = {
    id: number;
 };

 type EntityWithComponents<ComponentKeys extends (keyof Components)[]> =
    Entity & {
        [P in ComponentKeys[number]]: Components[P]
    };

 declare function entityWith<ComponentKeys extends (keyof Components)[]>(components: ComponentKeys): EntityWithComponents<ComponentKeys>;

 const x = entityWith(['health', 'transform']);

 type X = typeof x; // 🎉 Entity & { health: Health; transform: Transform; }
	// components.ts
	type Component = Components[keyof Components]; // Health \| Transform

	interface Components { /* add new components to this interface in separate files */ }

	// health.ts
	type Health = number & { __brand: 'Health' };

	interface Components {
	health: Health;
	}

	// transform.ts
	class Transform { };

	interface Components {
	transform: Transform;
	}

	// entity.ts
	type Entity = {
	id: number;
	};

	type EntityWithComponents<ComponentKeys extends (keyof Components)[]> =
	Entity & {
	[P in ComponentKeys[number]]: Components[P]
	};

	declare function entityWith<ComponentKeys extends (keyof Components)[]>(components: ComponentKeys): EntityWithComponents<ComponentKeys>;

	const x = entityWith(['health', 'transform']);

	type X = typeof x; // 🎉 Entity & { health: Health; transform: Transform; }