CODEWITHSUNDEEP
rxjs
Picci
Picci

Reputation: 17762

accumulating values such as with scan but with the possibility to reset the accumulator over time

I have one Observable, obs1, which represents a stream of numbers over time. I need to accumulate the sum of such numbers and emit it progressively (i.e. a long way to say I need to use scan operator).

Then there is a second Observable, obs2, that represents some sort of "reset time". In other words, when obs2 emits, I have to reset the accumulator I have set on obs1 and start summing from 0.

I think I have been able to reach the behavior I want with the following code, but I am not sure it is the right way to do it (it sorts of smells to me)

const obs1 = Observable.interval(100).mapTo(1).take(100);

const obs2 = Observable.interval(700).take(10);

obs1.pipe(
    windowWhen(() => obs2),
    mergeMap(d => d.pipe(scan((acc, one) => acc + one, 0)))
)
.subscribe(console.log);

Any suggestion on how to improve it?

Upvotes: 4

Views: 1377

Answers (1)

Picci
Picci

Reputation: 17762

Probably something like this is what i was looking for

const obs1 = Observable.interval(100).mapTo(1).take(100);

const obs2 = Observable.interval(700).take(10);


function scanReset(seed) {
    return obs1.pipe(
        scan((acc, one) => acc + one, seed)
    )
}

obs2.pipe(
    switchMap(() => scanReset(0))
)
.subscribe(console.log);

Upvotes: 4

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