Observable vs Subject and asObservable

Question

I am learning RxJs, I am seeking confirmation or correction on my assumption.

I am trying to make a public read only observable in a servic

Answer 1

What you're doing is correct. There's however still a little shorter notation. Since Subject is already an Observable (it inherits the Observable class) you can leave the type checking to TypeScript:

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

Any consumer of your service can subscribe to myObservable$ but won't be able to call myObservable$.next() because TypeScript won't let you do that (Observable class doesn't have any next() method).

This is actually the recommended way of doing it and RxJS internally never uses asObservable anyway. For more detailed discussion see:

• https://github.com/ReactiveX/rxjs/pull/2408

• https://github.com/ReactiveX/rxjs/issues/2391

See a very similar question: Should rxjs subjects be public in the class?

Answer 2

In project we are using this kind of Observables, this is giving you proper encapsulation to your private observable, but you still can call next() using some public method.

      private sourceName = new Subject<T>();
      name = this.sourceProductName.asObservable();

      sendName(item: T) {
        this.sourceName.next(item);
      }