CODEWITHSUNDEEP
javascriptangular
Umair
Umair

Reputation: 3243

angular 2 conditional chaining of observables

I have a modal popup, which I am coding such that when an open() function is called, it returns an observable. Any subscriber will then get an object with a property indicating what button was pressed in the modal or whether it was closed, etc.

If a 'success' button is pressed, I want to make a http call, which in turn also returns an observable! How would I combine these two observables? In angular 1 with promises I can return promises from promises, so I would do something like

 var promise = modal.open()
                    .then(function(res) { 
                        if (res.success) {
                            return httpService.get(); // also returns a promise
                        }

                        return res;
                    });

how would I do something like this for observables?

Upvotes: 1

Views: 1942

Answers (1)

Thierry Templier
Thierry Templier

Reputation: 202256

You can leverage observable operators to build an asynchronous data flow. In you case, the switchMap operator:

var observable = modalObservable.switchMap(() => {
  return return httpService.get(); // also returns an observable
});

Be careful to import the operators you need since they aren't by default (see this question: Angular 2 HTTP GET with TypeScript error http.get(...).map is not a function in [null]):

import 'rxjs/add/operator/switchMap';

You could have a look at the following article and presentation for more details:

Upvotes: 1

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