Followup question to a discussion a while back: <h...

# compose

[Jason Ankers]

Followup question to a discussion a while back: https://kotlinlang.slack.com/archives/CJLTWPH7S/p1614609620302500?thread_ts=1614345603.389700&amp;cid=CJLTWPH7S

What would be the best way to collect a cold data source like this (scoped to the composable), but also keep a reference to it in the viewmodel? The viewmodel needs to keep a reference because we keep a bunch of derivedStateOf business logic inside it

[Adam Powell]

do you have a more specific example?

[Jason Ankers]

I want to subscribe to some data when my composable first appears on the screen (and have the subscription scoped to my composable). The composable has some heavy business logic associated with it, so all of the state is kept inside a ViewModel. The strategy in that thread shows how you can subscribe to a cold data source with collectAsState , but collectAsState is only available in composable functions so I’m not sure how I can reference it in my ViewModel:

@Composable
fun ViewExercise(id: String) {
    val viewExerciseViewModel: ViewExerciseViewModel = hiltNavGraphViewModel()
    
    // I want to access this in the ViewModel
    val exercise by remember { viewExerciseViewModel.exerciseFlow(id) }.collectAsState()
    ..
}

class ViewExerciseViewModel {
    val equipment = derivedStateOf {
       // some derived state of `exercise`
    }
}