Hi all -- I have a Flow<> and for each item,...

# coroutines

[jeff]

Hi all -- I have a Flow<> and for each item, I want to make a potentially-long-running network call. I would like these calls to happen in parallel.

I can achieve that by doing

myFlow
.flatMapMerge { item ->
    flow { emit(suspendingFunctionThatMakesNetworkCall(item)) }
}

HOWEVER, Flow's flatMapMerge() has the following comment

Note that even though this operator looks very familiar, we discourage its usage in a regular application-specific flows.
Most likely, suspending operation in [map] operator will be sufficient and linear transformations are much easier to reason about.

I can't figure out how to do this with just a suspend map. Help?

[octylFractal]

I'm not sure if this is really any better, but I think doing .transform { flow -> coroutineScope { flow.map { async { suspendingFunction(it) } }.buffer(N).emitAll() } } might work out better / be more specific

[octylFractal]

basically you launch up to N+1 concurrent async tasks, then after you can await and emit them

[jeff]

interesting, let me try it