RXJS Observable Transform Array To Multiple Values

Question

I'm making an Angular 2 HTTP get request and in return I get Observable<Message[]> I want to transform this observable into multiple emit. So let's say the server returned Message array with length 3. I would like to get 3 notification in my subscribe call (on for each value in the array) instead of getting one call with the array.

e.g : ['Hello','Hey','Howdy'] - > 'Hello', 'Hey','Howdy'

I found an operator that does transform the array (Observable.for), but this operator takes as an argument an array and not an Observable.

martin · Accepted Answer · 2017-09-15 12:59:19Z

8

You can use the concatAll operator to flatten the array (mergeAll will work as well).

Observable.of(['Hello','Hey','Howdy'])
  .concatAll()
  .subscribe(console.log)

See demo: https://jsbin.com/gaxajex/3/edit?js,console

edited Sep 15, 2017 at 12:59

answered Jun 13, 2017 at 7:17

martin

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1 Comment

MasterOfPuppets Over a year ago

Thank you! Exactly what I was looking for.

SasaT · Accepted Answer · 2017-06-13 13:33:56Z

3

Try this:

Observable.from(yourRequest())
    .flatMap(msgList => Observable.from(msgList))
    .subscribe(msg => console.log(msg));

yourRequest() in this case should return array.

If yourRequest() returns Observable then:

yourRequest().flatMap(msgList => Observable.from(msgList))
    .subscribe()

answered Jun 13, 2017 at 13:33

SasaT

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1 Comment

golfadas Over a year ago

since msgList carries over to Observable.from, flatMap(msgList => Observable.from(msgList)) can be written as ` .flatMap(Rx.Observable.from) `

ulubeyn · Accepted Answer · 2017-06-13 07:02:54Z

0

If I understand you well, you want to use something like concatMap. By using concatMap, you can map values(Message array in your case) to inner observable, and then you can subscribe these values in order.

yourRequest.concatMap(i: Message => Observable.of(i)).subscribe(i => {
     //sendNotification(i);
});

You can also take a look at this page.

I hope it helps!

answered Jun 13, 2017 at 7:02

ulubeyn

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