Hi all, I have an architecture issue with a compos...

# compose

[gpaligot]

Hi all,
I have an architecture issue with a composable and a Kotlin Flow from a ViewModel. In my ViewModel, I have a flow which observes any changes in a room database to emit a data with a delay. Here a small example of my ViewModel:

fun myFunc(input: Input) = flow {
  myDao.get().collect {
    it.forEach {
      emit(it.data)
      delay(it.delayTime)
    }
  }
}

In my composable, I have something like this:

@Composable
fun MyComposable(input: Input) {
  val myViewModel: MyViewModel = viewModel()
  val data = myViewModel.myFunc(input).collectAsState()
  AnotherComposable(data = data.value)
}

The issue is: When I emit new data from my flow, compose collect the data and recompose itself because the state has been updated but due to this recomposition, it recall myFunc function, cancel the previous execution of the flow, collect data from database, emit values and loop a long time like this.
How can I change my code to avoid this loop? There is any good practice for my usecase?
Thanks in advance!

[gpaligot]

For now, the only workaround I found is this:
Create a StateFlow in my ViewModel to emit my data and to avoid return a flow in myFunc and in my composable:

@Composable
fun MyComposable(input: Input) {
  val myViewModel: MyViewModel = viewModel()
  val inputState = remember { mutableStateOf(input.id) }
  onActive {
    myViewModel.myFunc(input)
  }
  onCommit {
    if (inputState.value != input.id) {
      myViewModel.myFunc(input)
      inputState.value = input.id
    }
  }
  val data = myViewModel.myStateFlow.collectAsState()
  AnotherComposable(data = data.value)
}

[Kshitij Patil]

This seems like a SideEffect and you should make use of one of them for your use-case.

1) I believe using produceState will make sure that myFunc() will be executed only once.

2) using kotlin's by to get the value out of flow would also make some difference (atleast I use it this way)

3) If you know some subject that causes the values being emitted via flow, you can use LaunchedEffect to call myFunc every time that subject changes

Also, I believe there should be no infinite loop by looking at the give code block as you're not using data.value in MyComposable anywhere and any changes in data.value should only recompose the AnotherComposable .

[gpaligot]

Thanks @Kshitij Patil, LaunchedEffect is exactly what I'm looking for!
But agree with you, data.value should only recompose the AnotherComposable