如何将承诺连接到这条链？

Question

I have a function that retrieve data of one user. Now I want to get in this function the user_id like that:

    this.storage.get(USER_ID).then(val => {
             this.id = val;
)}

so the api knows from which user it need the id. My main function I have to insert this is:

ngOnInit() {
    this.subscription = this.authService.authenticationStateSubject.pipe(
      switchMap(isAuthenticated => {
        if (isAuthenticated) {
          return this.userService.getUserDetails(this.id);
        } else {
          return of(null);
        }
      }),
    ).subscribe(
      result => {
        if (result) {
          this.information = result;
          console.log(this.information);
        } else {
        }
      },
      error => {
      }
    );
  }

I tried to put my snippet right after the if (isAuthenticated) { but somehow it doesn't work with the two last brackets. Can I actually connect these two snippets?

combined version

ngOnInit() {
    this.subscription = this.authService.authenticationState,
    from(this.storage.get(USER_ID))
    .pipe(
      switchMap(([isAuthenticated, id]) => {
        if (isAuthenticated) {
          return this.userService.getUserDetails(this.id);
        } else {
          return of(null);
        }
      }),
    ).subscribe(
      result => {
        if (result) {
          this.information = result;
          console.log(this.information);
        } else {
        }
      },
      error => {
      }
    );
  }

Answer 1

Use from to convert your promise to an observable and use combineLatest with the authenticationStateSubject

this.subscription = combineLatest(
  this.authService.authenticationStateSubject, 
  from(this.storage.get(USER_ID))
).pipe(
  switchMap(
    ([isAuthenticated, id]) => isAuthenticated ? this.userService.getUserDetails(id) : of(null)
  )
).subscribe(
  result => {
    // do stuff with result
  }
);