How can I emit the result to the consumer from a different function When I try the following nothing happens ```fun fetchInfo Flow lt State lt SportInfo gt gt = flow val result = memoryInfoResult if result = null emit result else fetchSportInfo onEach result gt when result is Data gt memoryInfoResult = result emit result is Error is Loading gt emit result ```

fun fetchInfo(): Flow<State<SportInfo>> =
    flow {
      val result = memoryInfoResult
      if (result != null) {
        emit(result)
      } else {
        fetchSportInfo()
        .onEach { result ->
          when (result) {
            is Data -> {
              memoryInfoResult = result
              emit(result)
            }
            is Error, is Loading -> {
              emit(result)
            }
          }
        }
      }
    }

Nick Allen

12/07/2021, 7:55 AM

Replace

onEach

with

collect

onEach

is not a terminating operator (not one that actually runs the flow).

👍 1

Also, this code is setup so if you have a cached result, you will never return anything else (updates are in an else).

And remember that

Flow

is cold. So if you have 5 collectors, then they are all updating

memoryInfoResult

. Usually for something with shared data, I prefer a

SharedFlow

. Should be able to just tack

.shareIn(someScope, SharingStarted.WhileSubscribed())

at the end which will run the flow only once for any number of subscribers at a time.

MRSasko

12/07/2021, 11:37 AM

thanx @Nick Allen. It helped to replace

onEach

with

collect

. I also had to change the

flow

builder to

channelFlow

, and replace

emit

with

send

. I only have one collector right now. But I might add more at some point.

Why is the

channelFlow

necessary in this example?

Nick Allen

12/07/2021, 5:31 PM

not sure, I wouldn't expect it to be needed from

collect

channelFlow

is needed any time you are dealing with multiple coroutine contexts which takes extra overhead to deal with correctly.

flow

is optimized for cases where you don't need that overhead.

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