fromCallback

Callable

• fromCallback<TEvent, TInput>(invokeCallback: InvokeCallback<TEvent, AnyEventObject, TInput>): CallbackActorLogic<TEvent, TInput>

---

• An actor logic creator which returns callback logic as defined by a callback function.

  @remarks

  Useful for subscription-based or other free-form logic that can send events back to the parent actor.

  Actors created from callback logic (“callback actors”) can:

  • Receive events via the receive function
  • Send events to the parent actor via the sendBack function

  Callback actors are a bit different from other actors in that they:

  • Do not work with onDone
  • Do not produce a snapshot using .getSnapshot()
  • Do not emit values when used with .subscribe()
  • Can not be stopped with .stop()

  @see

  • InvokeCallback for more information about the callback function and its object argument
  • docs for more information about how input is passed

  @example

  const callbackLogic = fromCallback(({ sendBack, receive }) => {
    let lockStatus = 'unlocked';
  
    const handler = (event) => {
      if (lockStatus === 'locked') {
        return;
      }
      sendBack(event);
    };
  
    receive((event) => {
      if (event.type === 'lock') {
        lockStatus = 'locked';
      } else if (event.type === 'unlock') {
        lockStatus = 'unlocked';
      }
    });
  
    document.body.addEventListener('click', handler);
  
    return () => {
      document.body.removeEventListener('click', handler);
    };
  });

  ---

  Type parameters

  • TEvent: EventObject
  • TInput = NonReducibleUnknown

  Parameters

  • invokeCallback: InvokeCallback<TEvent, AnyEventObject, TInput>

    The callback function used to describe the callback logic The callback function is passed an object with the following properties:

    • receive - A function that can send events back to the parent actor; the listener is then called whenever events are received by the callback actor
    • sendBack - A function that can send events back to the parent actor
    • input - Data that was provided to the callback actor
    • self - The parent actor of the callback actor
    • system - The actor system to which the callback actor belongs The callback function can (optionally) return a cleanup function, which is called when the actor is stopped.

  Returns CallbackActorLogic<TEvent, TInput>

  Callback logic