how to use multicasting obs with behavioursubject? - rxjs

Question

In general we need behavior subject functionality. But only on first subscription we should send subscribe to server in REST. And to send unsubscribe on the last unsubscribe, and all late observers subscribed will gwt the latest json recwived from the first. can i do it using rxjs operaTors and how? or shoul i use custom obserbale ?
currently the custom code for this is this:
public observable: Observable<TPattern> = new Observable((observer: Observer<TPattern>) => {
this._observers.push(observer);
if (this._observers.length === 1) {
this._subscription = this.httpRequestStream$
.pipe(
map((jsonObj: any) => {
this._pattern = jsonObj.Data;
return this._pattern;
})
)
.subscribe(
(data) => this._observers.forEach((obs) => obs.next(data)),
(error) => this._observers.forEach((obs) => obs.error(error)),
() => this._observers.forEach((obs) => obs.complete())
);
}
if (this._pattern !== null) {
observer.next(this._pattern); // send last updated array
}
return () => {
const index: number = this._observers.findIndex((element) => element === observer);
this._observers.splice(index, 1);
if (this._observers.length === 0) {
this._subscription.unsubscribe();
this._pattern = null; // clear pattern when unsubscribed
}
};
});

Answer 1

Sounds like you need a shareReplay(1), it will share the latest response with all subscribes.
const stream$ = httpRequestStream$.pipe(
shareReplay(1),
),
stream$.subscribe(); // sends the request and gets its result
stream$.subscribe(); // doesn't send it but gets cached result
stream$.subscribe(); // doesn't send it but gets cached result
stream$.subscribe(); // doesn't send it but gets cached result