Comparing Observable and Subject, plus the usage of asObservable

Currently delving into the world of RxJs, I would appreciate any verification or correction regarding my assumption.

Incorporating a public read-only observable in a service, which allows me to utilize .next() at different points within my service class. Here is what I have implemented:

private myObservable = new Subject<T>();
public myObservable$: Observable<T> = this.myObservable.asObservable();
  • Users can subscribe to myObservable$
  • I can usemyObservable.next(...);

While it functions perfectly fine, I acknowledge that there might be potential errors given my limited experience with RxJS. Is this the correct approach and suitable object for this particular scenario?

javascriptangulartypescriptrxjsangular-services

Answer №1

Your current approach is accurate, but there's a slightly more concise notation available. Since Subject already extends the Observable class, you can rely on TypeScript to handle type checking for you:

private myObservable = new Subject<T>();
public myObservable$: Observable<T> = this.myObservable;

By exposing myObservable$, consumers of your service can subscribe to it without being able to call myObservable$.next() due to TypeScript restrictions (since Observable doesn't have a next() method).

This is actually the recommended practice, and internally RxJS does not use asObservable. For further discussion, refer to:

You may also find a related question here: Should rxjs subjects be public in the class?

Answer №2

Our project utilizes Observables in this specific manner, allowing for proper encapsulation of private observables while still providing the ability to call next() using a public method.

      private dataStream = new Subject<T>();
      observableData = this.dataStream.asObservable();

      sendData(item: T) {
        this.dataStream.next(item);
      }

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