I need builder like `callbackFlow` but I do not need `awaitClose()` callback. What would be a good ...

# coroutines

[K Merle]

I need builder like callbackFlow but I do not need awaitClose() callback. What would be a good candidate for it in flow?

[Chrimaeon]

why not just leaving the awaitClose() block empty?

[K Merle]

For now I am, I was just wondering if there is any other flow builder type that can emit values from non suspend functions.

[Chrimaeon]

not sure what you mean but

fun foo() = flow {
  emit(true)
}

this is a valid “flow”

[Chrimaeon]

so actually if you don’t need the awaitClose() that callbackFlow provides you can use the basic flow builder.

[Oleg Yukhnevich]

What about 'channelFlow'?

[K Merle]

I do have to implement async callback function inside of that flow builder. Calling emit inside of the lambda gives me compile warning in a sense "emit can only be called within suspend function".

[K Merle]

@Oleg Yukhnevich I should look into it. Just tried it and nothing is being emitted from within channelFlow body, like no one is consuming it. I'll look into it. For now best option seems to just leave awaitClose() empty as @Chrimaeon suggested.

[Nick Allen]

channelFlow and callbackFlow are the same except callbackFlow now throws if you don’t call awaitClose (it didn't in the past). The channel is closed when the generator lambda completes. That’s why you need awaitClose there even if there's nothing to clean up.

Btw, if you can change code such that there is a way to clean up in awaitClose, I’d go ahead and do I it. Without that you are likely leaking something beyond your coroutine and that can cause subtle bugs ( like a resource used by a leaked listener after it's been closed).

[louiscad]

You can also use awaitCancellation() FYI.

[Michal Klimczak]

That's what Turbine does btw