So I asked a question on SO <here> about why the `composable` for a route was being recomposed when...

# compose

[Jesse Hill]

So I asked a question on SO here about why the composable for a route was being recomposed whenever the state inside my HiltViewModel changed. After thinking through it a bit I think I know the answer but wanted some confirmation before updating the post. I’ll put what I think is going on in the thread.

[Jesse Hill]

So I think that the reason the composable is being recomposed is because when I put a mutableStateOf value in the ViewModel that is basically the same thing as if I structured the composable like this:

composable("route") {
  var count by mutableStateOf(0)
  
  HomeScreen(count, updateCount = { count++ })
}

@Composable
fun HomeScreen(
    homeCount: Int,
    updateCount: () -> Unit,
) {
    Log.i("Home", "Home Screen")
    Column(modifier = Modifier.fillMaxSize()) {
        Spacer(modifier = Modifier.height(25.dp))
        Button(onClick = { updateCount() }) {
            Text("Increment count")
        }
        Spacer(modifier = Modifier.height(25.dp))
        Text("Count is: $homeCount")
    }
}

Am I right to assume that anytime there is a state value either directly in the composable (or in a ViewModel being injected into the composable) that the composable containing the value with recompose if the state value changes?

[Marko Novakovic]

yes. having State inside ViewModel is just hoisting it (moving it step above) but State is still State and behaviour around it is still the same

[Jesse Hill]

Thanks!

[Marko Novakovic]

no problem

[Marko Novakovic]

recently here was a discussion about it

[Marko Novakovic]

@Jesse Hill https://kotlinlang.slack.com/archives/CJLTWPH7S/p1623313858334200