I am testing Flow with Observables having this code ``` runB kotlinlang #coroutines

runBlocking(<http://Dispatchers.IO|Dispatchers.IO>) {
        val myList = mutableListOf(1).asObservable()

        launch {
            myList.asFlow().collect { println("A $it") }
        }

        delay(1000)

        myList += 2

        launch {
            myList.asFlow().collect { println("B $it") }
        }

        delay(1000)
    }

Which produces:

A 1
B 1
B 2

Is there some sort of non-terminal

collect

yet that would listen for further changes, so that I would see

A 2

in the output when

myList

gets updated?

Zach Klippenstein (he/him) [MOD]

04/28/2019, 4:16 PM

This isn’t an RxJava or Flow issue, you’re asking for a version of

MutableList

that sends change notifications. One thing you could do is use a

BehaviorSubject<List<Int>>

and push new lists in when you add/remove/change items.

littlelightcz

04/29/2019, 11:39 AM

Well, I thought that

.asObservable()

will do exactly this. Or at least for JavaFx components it works as expected - they update automatically when the list changes (if they are bound to it).

Zach Klippenstein (he/him) [MOD]

04/29/2019, 3:39 PM

Ah, I assumed

asObservable

turned a list of

[1]

into an

Observable

that just emitted

and then completed. Where does

asObservable

come from?

littlelightcz

04/29/2019, 9:07 PM

I think it comes with the TornadoFX lib 😊

Zach Klippenstein (he/him) [MOD]

04/29/2019, 10:35 PM

ah, not familiar with that one. sorry for the confusion!

I read the

ObservableList

docs and I think I understand what you meant now. It seems like the simplest thing to do would be to create a

Flow<ListChangeListener.Change<T>>

and then handle changes manually. I'm not sure how you would convert that into a simple flow of elements though - you can emit added elements, but how would you handle changed or removed elements? E.g.

val changes = flowViaChannel(bufferSize = UNLIMITED) { ch ->
  val listener = ListChangeListener {
    ch.offer(it)
  }
  myList.addListener(listener)
  ch.invokeOnClose { 
    myList.removeListener(listener)
  }
}

littlelightcz

04/30/2019, 12:39 PM

Hmh, interesting question about the removing😁

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