Angular 15 create observable function referencing local variables

Question

The observable function is NOT http; the function must be local, but it needs to be subscribed. This is the best I could do based on online example:

export class AppComponent implements OnInit {
  title = 'Sample';
  message1 = '';

  observable = new Observable((subscriber) => {
    subscriber.next(1);
    subscriber.next(2);
    subscriber.next(3);
    setTimeout(() => {
      subscriber.next(4);
      subscriber.complete();
    }, 1000);
  });    


  constructor() {}

  ngOnInit() {
  }   

  public getUser() {
      this.observable.subscribe({
        next(x) {
          this.message1 = 'got value ' + x;  <--------------------------
        },
        error(err) {
          console.error('something wrong occurred: ' + err);
        },
        complete() {
          console.log('done');
        },
      });
      console.log('just after subscribe');
    }
}

The subscriber has no access to anything outside of itself (the message1 I show with arrows). Thoughts?

Adrian Brand · Accepted Answer · 2023-03-13 00:46:31Z

1

Have you looked at a Subject? A subject is both an observable and an observer and exposes it's next method.

const { Subject } = rxjs;

obs$ = new Subject();

obs$.subscribe(val => { console.log(val); });

obs$.next(1);
obs$.next(2);
obs$.next(3);
setTimeout(() => {
  obs$.next(4);
  obs$.complete();
}, 1000);

<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/7.8.0/rxjs.umd.min.js"></script>

There is also BehaviorSubject that stores the most recently emitted value for new subscribers and ReplaySubject that stores a buffer of emitted values.

edited Mar 13, 2023 at 0:46

answered Mar 13, 2023 at 0:40

Adrian Brand

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