what is the proper way of transforming a flow<L...

# coroutines

[myanmarking]

what is the proper way of transforming a flow<List<T>> to a flow<T> ?

[streetsofboston]

Flatmap?

val listflow: Flow<List<Int>> = ...
val itemFlow: Flow<Int> = listFlow.flatMapConcat { it.asFlow() }

(not sure if Collection<T>.asFlow() or something similar exists, but it would not be hard to write yourself if it doesn’t)

[myanmarking]

i mean an operator on flow

[myanmarking]

managed to make this one:

fun <T> Flow<List<T>>.flatten(): Flow<T> {
    return flow {
        collect { values -> values.forEach { value -> emit(value) } }
    }
}

[myanmarking]

i think it should work as intended

[araqnid]

I’ve used flatMapConcat { it.asFlow() } or flatMapMerge { it.asFlow() } — flattening flows is potentially a bit more involved than a plain sequence

[Dominaezzz]

Use transform for transforming flows.

fun <T> Flow<List<T>>.flatten(): Flow<T> {
    return transform { values ->
        values.forEach { value -> emit(value) }
    }
}

[myanmarking]

ok. thanks

[araqnid]

transform will always apply the transforms in series, not in parallel