CODEWITHSUNDEEP
angularrxjs
Davy
Davy

Reputation: 6441

RxJS alternative to doing a Promise.resolve?

What is the equivalent in RxJS to Promise.resolve? I know I can do Observable.fromPromise(Promise.resolve(someValue)); but there has to be a cleaner way.

Upvotes: 36

Views: 25278

Answers (2)

PeregrineYankee
PeregrineYankee

Reputation: 75

Promise.resolve(), if given a promise, will return an identical promise. It’s essentially a no-op, but it’s a useful way to ensure that whatever “thing” you have is promise-wrapped.

Observable.of(), by contrast, if given an observable, is not a no-op; it will return an observable that wraps the original observable.

For of() to be comparable to this aspect of Promise.resolve, the output here:

rxjs.of( rxjs.of(1,2,3) ).subscribe( { next: v => console.log(v) } )

… should be 1, 2, 3, but instead it’s 3 observables.

Unfortunately, I don’t know of an RxJS operator that can do this.

Upvotes: 0

alexpods
alexpods

Reputation: 48525

Observable.of is what you are looking for (see this plunk):

// You might need to add this import in RxJS versions earlier than 5
import 'rxjs/add/observable/fromArray';

// ... or this line in RxJS 5+
import 'rxjs/add/observable/of';

if (me.groups) {
  return Observable.of(me.groups);
}

Upvotes: 34

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