RxJS - Multiple sources for .withLatestFrom

Question

I want to merge the latest emitted values from multiple Observables, so right now I'm using .withLatestFrom. Except, it nests the data together in nested arrays instead of pushing the data into a new array value. Example code below.

Any ideas on how I can retrieve multiple Observable emits using .withLatestFrom?

source0
  .withLatestFrom(source1)
  .withLatestFrom(source2)
  .withLatestFrom(source3)
  .map((data) => { console.log(data) });

score 128 · Accepted Answer · answered Apr 19 '17 at 18:50

128

withLatestFrom supports multiple observables:

.withLatestFrom(source1, source2, source3)
.map((data) => { console.log(data) });

-> [val, value1, value2, value3]

It also supports function as it's last parameter, so you can get values other than arrays:

observable$
    .withLatestFrom(source1, source2, (val, one, two) => {
        return {val: val, one: one, two: two};
     });

answered Apr 19 '17 at 18:50

adharris

3,591
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7

You can wrap the `{}` with `()` then you don't need an explicit return statement : `.withLatestFrom(source1, source2, (val, one, two) => ({ val: val, one: one, two: two }));` – Simon_Weaver Jun 21 '17 at 19:05

score 9 · Answer 2 · answered Apr 19 '17 at 18:56

9

withLatestFrom accepts multiple observables. so you can write it like:

let obs1$ = Rx.Observable.of('a');
let obs2$ = Rx.Observable.of('b');

Rx.Observable.interval(1000)
  .withLatestFrom(obs1$, obs2$)
  .subscribe(x=>console.log(x))

answered Apr 19 '17 at 18:56

Julia Passynkova

17,256
6
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RxJS - Multiple sources for .withLatestFrom

2 Answers2