如何让我的 Angular BehaviorSubject 触发？

Question

I have the following set up, but it doesn't work. I never see the alert popup.

// this is in ngOnInit
  this.getBackDate$.subscribe();

//this.$spService.clientProfile$ is as follows:
 
public clientProfile$: Observable<ClientProfile | null> = this.client$.pipe(
    tap(()=> this.clientProfileIsLoading$.next(true)),
    switchMap( (client) => {
      if (!client) {
        return  of<ClientProfile>(null);
      }
      return this.$http.get<ClientProfile>(ApiDomain.supervisionPlan, `/v1/Client/ClientProfile?clientIdToken=${client.entityIdToken}`)
    }),
    tap(() => this.clientProfileIsLoading$.next(false))
  );

...

  getSelectedClient$ = new BehaviorSubject<ClientProfile>(null);

  getBackDate$ = this.getSelectedClient$.pipe(
    withLatestFrom(this.$spService.clientProfile$),
    tap(([client]) => {
      alert(client.caseStart)
      this.maxBackdate = client.caseStart;
    })
  );

EDIT:

If I change to this it works, but I don't want to use combineLatest, as I am not combining anything.

  getBackDate$ = combineLatest([this.$spService.clientProfile$]).pipe(
    tap(([client]) => {
      alert(client.caseStart)
      this.maxBackdate = client.caseStart;
    })
  );

Answer 1

If you have a look here you can see that both observables need to emit a value. Otherwise nothing will happen. So you could do the following:

clientProfileReplay$ = this.$spService.clientProfile$.pipe(
   shareReplay({ bufferSize: 1, refCount: true })
);

And then use clientProfileReplay$ in withLatestFrom().

Seems like an asynchronous bug you have got there