let's say you have 2 observables:
const obs1$: Observable<string[]> = this.getObs1$();
const obs2$: Observable<string[]> = this.getObs2$();
i want to combine these 2 so that in subscription (or rxjs map) i know which emitted the values. I can't use combineLatest because for the other observable i just get the latest value it emitted at some point.
There doesn't seem to be a purely RxJS solution to this (but hopefully someone can prove me wrong on that!)
You could use a variable in the outter scope to track the emitting observable as a workaround
let trigger: TriggerEnum;
const obs1$: Observable<string[]> = this.getObs1$()
.pipe(tap(() => trigger = TriggerEnum.One));
const obs2$: Observable<string[]> = this.getObs2$()
.pipe(tap(() => trigger = TriggerEnum.Two));;
combineLatest(....).subscribe(
// check trigger value
);
From the docs as a just-in-case: be aware that combineLatest will not emit an initial value until each observable emits at least one value
You can use merge to combine the two observables into a single observable. Then, do what @martin suggested and map each source's emissions to a little structure that allows you identify the source:
const obs1$: Observable<number[]> = getNumbers();
const obs2$: Observable<string[]> = getLetters();
const combined$ = merge(
obs1$.pipe(map(data => ({ source: 'obs1$', data }))),
obs2$.pipe(map(data => ({ source: 'obs2$', data })))
);
combined$.subscribe(
({ source, data }) => console.log(`[${source}] data: ${data}`)
);
// OUTPUT:
//
// [obs1$] data: 1
// [obs2$] data: A
// [obs2$] data: A,B
// [obs2$] data: A,B,C
// [obs1$] data: 1,2
// [obs2$] data: A,B,C,D
...
Here's a little StackBlitz example.