Chaining observables with RxJS in Angular2

Question

I have 2 API calls -- the second call uses something the first call returns. With promises this was easy:

myService.findAll()

     // First call
    .then(response => {
        return myService.findSpecific(response.something);
    })

    .then(response => {
        // result from second API call
    });

How would I do this using observables?

A good thing to remember is that in RXJS Promises can be treated as Observables that will at most emit a single item (the resolved data). — Calvin Belden
– Calvin Belden, Commented Apr 25, 2016 at 14:42

Thierry Templier · Accepted Answer · 2016-04-25 11:02:53Z

8

You can leverage the flatMap operator this way:

myService.findAll()
  // First call
  .flatMap(response => {
    return myService.findSpecific(response.something);
  }).subscribe(response => {
    // result from second API call
  });

answered Apr 25, 2016 at 11:02

Thierry Templier

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1 Comment

Sander Over a year ago

Thank you, this answer helped me! +1

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