What would be the idiomatic way to subscribe to `f...

# coroutines

[zak.taccardi]

What would be the idiomatic way to subscribe to flowB when val flowA: Flow<Boolean> emits true, and unsubscribe from flowB when flowA emits false?

[zak.taccardi]

flowA.distinctUntilChanged()
.flatMapLatest { shouldSubscribe: Boolean ->
    if (shouldSubscribe) {
        flowB
    } else {
        emptyFlow()
    }
}
.launchIn(this)

[zak.taccardi]

maybe?

[octylFractal]

that seems to work pretty well

[Tash]

yup flatMapLatest looks like the way to go

[gildor]

offtopic: I’m still confused with name flatMapLatest, switchMap makes more sense for me.
I almost start arguing that switchMap is the way to implement this, until I realised that flatMapLatest is the same

Of course I’m biased, too many years of RxJava usage, but still “switch” which actually helps me understand what this function does

[Tash]

@gildor yeah. saw that there was this discussion re: the name https://github.com/Kotlin/kotlinx.coroutines/issues/1335

Taken from there:

This nomenclature produces the following distinctly named variants of flatMap operator with different merging strategies:

• `flatMapConcat`/`flattenConcat` -- concatenates all flows.
• `flatMapLatest`/`flattenLatest` -- cancels ongoing flow as soon as the new one appears.
• `flatMapMerge`/`flattenMerge` -- concurrently run flows and merge their results.

Got more context on the name after reading that.

[gildor]

Yes, I’m aware about this renaming, just still not convinced

[gildor]

Now instead I’m confused about all 3 of them 🙈