Angular RxJS Nested Subscribe with multiple Http Requests

Question

I would like to know what is the best practice when making http request one after another, especially, I'll be required to use the return value from the first request. Currently, I've a nested subscription to achieve this issue [See the code below].

I tried with siwtchMap, mergeMap & concat from RxJS, but it didn't seem to work. Any suggestion will be help for.

onStartUp() {
    this.recordingService.getRecording(this.id)
     .subscribe(x => {
       this.recording = x;
       const params = new Chunk(this.recording, 0, 30);
       this.recordingService.getSignal(params)
        .subscribe(data => console.log(data));
     });
  }

What didn't work with switchMap or mergeMap?

martin
– martin

2018-07-03 10:23:21 +00:00
Commented Jul 3, 2018 at 10:23 — martin
– martin, Commented Jul 3, 2018 at 10:23

Daniel Caldera · Accepted Answer · 2018-07-03 08:30:21Z

2

Why switchMap does not work in your case? I think it is the best solution, switchMap receive the result of the stream and return another observable to continue the stream:

onStartUp() {
   this.recordingService.getRecording(this.id)
   .switchMap((x) => {
       this.recording = x;
       const params = new Chunk(this.recording, 0, 30);
       return this.recordingService.getSignal(params);  
   })
   .subscribe(data => console.log(data));
 }

In case you are using pipeable operators:

import { switchMap } from 'rxjs/operators';

this.recordingService.getRecording(this.id)
  .pipe(
      switchMap((x) => {
          this.recording = x;
          const params = new Chunk(this.recording, 0, 30);
          return this.recordingService.getSignal(params);  
      })
  )
  .subscribe(data => console.log(data));

edited Jul 3, 2018 at 8:30

answered Jul 3, 2018 at 8:12

Daniel Caldera

1,1291 gold badge9 silver badges17 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Angular RxJS Nested Subscribe with multiple Http Requests

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related