rxjs concatMap does not seem to be called

Question

The 2nd concatMap does not get called.

this.apiService.get()
               .pipe(
                   concatMap((data: MyModel) => {
                       if (data) {
                           // the following returns a MyModel Observable
                           return this.apiService.update(data);
                       } else {
                           return empty();
                       }
                   }),
                   concatMap((data: MyModel) => this.apiService.update(this.myOtherData))
               )
               .subscribe(data => log('completed'));

any ideas?

Answer 1

You'd have to double pipe. Take a look here: https://github.com/reactivex/rxjs/issues/4071

timer(10).pipe(
  concatMap(() => from(wait(20)).pipe(
    concatMap(() => {
      console.log('here');
      return from(wait(20)).pipe(
        tap(x => console.log('>', x))
      );
    })
  ))
)
.subscribe(x => console.log('>', x));

You know how concatMap requires an observable to return? Well I just learned that if there is an issue with that source observable concatMap won't fire. I was stumped trying to troubleshoot concatMap when it wasn't the cause.

This is how I troubleshot it too, by sending an empty observable to make sure my setup was correct.

this.sendRequest({'search': "be"}).pipe(
    concatMap(options => {
        console.log(options);
        return of([]);
    })
).subscribe(data => {
     console.log(data);
});