Difference between Actor and ActorRef

[alexamy]

I am a little puzzled with difference between these two. Especially looking into @xstate/solid useActorRef, simplified version below:

import { createActor } from 'xstate';

function useActorRef(...): ActorRef {
  const actorRef = createActor(...); // type is `Actor`
  return actorRef as any; // type becomes `ActorRef`
}

What are the differences, and why can’t they be used interchangeably?

[davidkpiano]

For most intents and purposes, the two should be able to be used interchangeably. In short, Actor implements ActorRef but has a few extra methods.

Can you share code where this is not working as expected?

[alexamy]

I am using XState 5.13.0. This code has type errors for both Actor and ActorRefFrom types from xstate:

import { ActorRefFrom, Actor, createActor, setup } from 'xstate';

const child = setup({}).createMachine({
  id: 'child machine',
});

const parent = setup({
  types: {
    input: {} as { children: ActorRefFrom<typeof child> }, // <-- Actor<typeof child> is not working too
    context: {} as { children: ActorRefFrom<typeof child> }, // <-- Actor<typeof child> is not working too
  },
}).createMachine({
  id: 'parent machine',
  context: ({ input }) => ({
    children: input.children,
  }),
});

const childActor = createActor(child);
const parentActor = createActor(parent, {
  input: {
    children: [childActor], // <-- Type error here: 
    // Type 'Actor' is missing the following properties from type 'ActorRef'
  },
});

The parent machine purpose is to control actors that have already been spawned by the external code.

[davidkpiano]

Why is it in an array? There is no type error if you move it out of the array:

const parentActor = createActor(parent, {
  input: {
-   children: [childActor],
+   children: childActor,
  },
});

[alexamy]

Thanks, my bad.