How to emit events from actor logic such as fromObservable

[reramjiawan]

Hi,

I have a question regarding emitting from actorLogic which is invoked such as fromObservable or fromPromise. When I emit using the provided emit method from the actorLogic I don't understand why this event is not bubbling up to the parent when listening for events.

Example:

const subject = new Subject();

const observableLogic = fromObservable<unknown, any, AnyEventObject>(({ emit }) => {
  return subject.pipe(
    tap((v) => {
      emit({ type: 'EMITTED', value: v });
    })
  );
});

const parentMachine = createMachine({
  initial: 'idle',
  states: {
    idle: {
      invoke: {
        src: observableLogic,
        onDone: {
          target: 'done',
        },
      },
      on: {
        EMITTED: {
          actions: emit({
            type: 'test',
          }),
        },
      },
    },
    done: {},
  },
});

const service = createActor(parentMachine);

service.on('*', (emitted) => {
  console.log('emitted?');
});

service.on('EMITTED', (emitted) => {
  console.log('emitted?');
});

service.start();

// Emit a value from the Subject
subject.next('Hello, world!');
subject.complete();

Please let me know if I am doing something wrong here or my expectations are not right.

[reramjiawan]

After playing around with XState I have found better suitable patterns. Thanks!

[GabrielAPineiro]

If you don't mind me asking, what was your solution for this case? I'm having the same issue, and I'm not understanding why the event is not being called. I have another machine with a similar case and the event is being fired with no problems

[reramjiawan]

Hi @GabrielAPineiro,

See this part in the docs https://stately.ai/docs/invoke#invoking-event-observables. Just return events from your observables and the rest is handled by the machine. From there you can do whatever you need, sendTo or whatever else.

[GabrielAPineiro]

That's crazy. I have a machine which worked with fromObservable, same logic of actor returning event and it being called automatically. But my second machine only worked with the fromEventObservable.
Thank you for the help!

[matheo]

@reramjiawan are you using fromObservable in the latest version?
@Andarist I'm streaming EventObjects and trying to use the emitter inside the action logic with no avail.

the workaround I found so far is this one:

              onSnapshot: {
                actions: enqueueActions(({ enqueue, event }) => {
                  if (event.snapshot.context) { // omit the first empty snapshot
                    enqueue.raise(event.snapshot.context as any);
                  }
                }),
              },

but this is not the idea of the library right?
it's NOT easy 😅

[matheo]

I see Event observables working, but I don't see event.output with fromObservable.

I'm doing an API call with Angular rxjs but the result is not propagated to onDone nor onSnapshot.
The documentation mentions that the data is saved to the fromObservable actor context, but how to access it?

PD. I had a target inside onSnapshot so I wasn't able to see the event data in the second call.
I expected no empty snapshot when the actor is invoked, only when the Observable emitted tho.

[davidkpiano]

Can you please share the code? The result should be present in onSnapshot.

The documentation mentions that the data is saved to the fromObservable actor context, but how to access it?

actor.getSnapshot().context