I have a `Channel` that I m converting to a flow and listeni kotlinlang #coroutines

that I'm converting to a flow and listening to. As soon as the channel is created I'm sending through an initial default value. Right before that happens I'm observing the

flow

using the onEach pattern. The flow, however, is not receiving the initial value, presumably because there's an asynchronous launch involved. Does anyone have any idea how to get around this issue?

octylFractal

04/02/2020, 7:22 PM

I don't think

onEach

observes the flow at all? are you eventually calling a terminal op like

launchIn

collect

☝️🏼 1

alexsullivan114

04/02/2020, 7:22 PM

Sorry yes I'm calling

launchIn

octylFractal

04/02/2020, 7:23 PM

not sure then, if you can provide an example that reproduces the issue I can look a little further

alexsullivan114

04/02/2020, 7:23 PM

Sure, one minute

object Woofers {
  fun doStuff(scope: CoroutineScope) {
    val channel = BroadcastChannel<Int>(Channel.BUFFERED)
    channel
        .asFlow()
        .onEach { println("Value: $it") }
        .launchIn(scope)

    // Won't be received
    channel.offer(1)
  }
}

That repros it

octylFractal

04/02/2020, 7:38 PM

yea, it looks like an ordering thing. I tried a few tricks, but I don't know if there's an easy way around it

if it works for you, using

flow.onStart { emit(1) }

might be a better solution

streetsofboston

04/02/2020, 9:56 PM

Is it only the first emission/value that goes missing?

What if you tried a regular Channel instead of a BroadcastChannel? I don’t see a reason why that would work, but i’m just curious 🙂

alexsullivan114

04/04/2020, 3:34 PM

I ended up using`flow.onStart`which worked. It could be more than the first value - presumably its all of the values until the launch call is up. I haven't tried a regular Channel I'll see if that makes a difference

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