how to run the code inside the subscribe function only once even though I subscribed multiple times-CodePudding

I subscribed multiple time to an observable but I want to run the callback function only once. is there any rxjs operator to do this?

this.store.select(MsnSelectors.getUserWhoTyping).subscribe(uts => {
        if (uts.length > 0) {
          let ut = uts.find(x => x.senderUserName === this.receiver.identifier);
          console.log(ut)
          ut?.isTyping ? this.userTyping = ut : this.userTyping = null;
        }
        else
          this.userTyping = null;
      })`

this portion of code is called several times (several subscription), so when the observable emit new value the code inside the subscribe method execute several times.

CodePudding user response：

var store = new Rx.ReplaySubject(1);
store.pipe(skip(1)).subscribe(uts => {
    if (uts.length > 0) {
      let ut = uts.find(x => x.senderUserName === this.receiver.identifier);
      console.log(ut)
      ut?.isTyping ? this.userTyping = ut : this.userTyping = null;
    }
    else
      this.userTyping = null;
  });

CodePudding user response：

You could perform your logic within a tap and then use the share operator to share your subscription so the logic is only executed once:

uts$ = this.store.select(MsnSelectors.getUserWhoTyping).pipe(
    tap(uts => /* your logic */ ),
    share()
);

subscription1 = this.uts$.subscribe();
subscription2 = this.uts$.subscribe();
subscription3 = this.uts$.subscribe();