How would I model this in flow I have a `Flow lt Int gt ` If it doesn t emit anything within 200ms emit `0`

```private object Uninitialized fun Flow lt Int gt blubb Flow lt Int gt return onStart lt Any gt emit Uninitialized transformLatest value gt if value == Uninitialized delay 200 emit 0 else emit value as Int ```

If someone has a better solution tell me slightly smiling face

How would I model this in flow I have a `Flow lt Int gt ` If kotlinlang #coroutines

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Paul Woitaschek

09/24/2019, 6:40 AM

How would I model this in flow? I have a

Flow<Int>

. If it doesn't emit anything within 200ms, emit

Dennis Schröder

09/24/2019, 7:15 AM

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

Paul Woitaschek

09/24/2019, 7:17 AM

I found a solution which is not typesafe

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

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)
    }
  }
}

If someone has a better solution tell me 🙂

gildor

09/24/2019, 7:23 AM

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

Paul Woitaschek

09/24/2019, 7:26 AM

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

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

gildor

09/24/2019, 7:28 AM

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

09/24/2019, 7:28 AM

It was a port from rx java

In rxjava it was actually way more complicated involving connected observables

gildor

09/24/2019, 7:30 AM

Port of which operator? Or your own?

Paul Woitaschek

09/24/2019, 7:33 AM

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

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