title: Angular 5 Subscribe to an Observable inside SwitchMap
body: <p>I'm trying to subscribe to an inner Observable. Here is what I'm doing:</p>
  
  <pre class="lang-js prettyprint-override"><code>getDates() {
    if (this.booking.id) {
  
      this.jobService.findById(this.booking.id)
        .map(job =&gt; job[0])
        .switchMap((job) =&gt; {
          return job ? this.bookingService.findByPropertyId(job.property.id) : Observable.empty();
        }, (job: Job, bookings: Booking[]) =&gt; {
          this.mark_jobs_unavailable(job, bookings);
          return job;
        })
        .subscribe(job =&gt; {
          this.bookingJob = job;
        });
  
    }
  }
  </code></pre>
  
  <p>My code is working fine, The only thing I'm trying to achieve is to subscribe to changes of my Bookings as well. Currently as I'm not sure where should I subscribe to the Observable that I get from <code>bookingService.findByPropertyId</code>, My app does not reflect to changes happening in bookings collection. </p>