How would I model this in flow? I have a `Flow<...

# coroutines

[Paul Woitaschek]

How would I model this in flow? I have a Flow<Int>. If it doesn't emit anything within 200ms, emit 0?

[Dennis Schröder]

Maybe this will help:

https://kotlinlang.org/docs/reference/coroutines/cancellation-and-timeouts.html#timeout

[Paul Woitaschek]

I found a solution which is not typesafe

[Paul Woitaschek]

It basically builds on having a private object Uninitialized, emitting that in onStart and do a transformLatest which does a delay if it's an Uninitialized

[Paul Woitaschek]

private object Uninitialized

fun Flow<Int>.blubb(): Flow<Int> {
  return onStart<Any?> { emit(Uninitialized) }.transformLatest { value ->
    if (value == Uninitialized) {
      delay(200)
      emit(0)
    } else {
      emit(value as Int)
    }
  }
}

[Paul Woitaschek]

If someone has a better solution tell me 🙂

[gildor]

It’s fine solution if you implement it as universal operator

[Paul Woitaschek]

Yeah, it's tested and lives in its own file

[Paul Woitaschek]

Actually it does something different than transforming ints but this was easier for an example 😉

[gildor]

Not sure about corresponding RxJava operator, you can do something like timeout() + onErrorReturnNext() but it’s not exactly the same (maybe only with onErrorReturn + check exception type)

[Paul Woitaschek]

It was a port from rx java

[Paul Woitaschek]

In rxjava it was actually way more complicated involving connected observables

[gildor]

Port of which operator? Or your own?

[Paul Woitaschek]

My own. It was transforming an observable<T> into an observable<LoadingState<T>>