Is there any difference between usage of remember ...

# compose

[Shakil Karim]

Is there any difference between usage of remember below ?

@Composable
fun ClubItem(club: Club,
             selectedClubs: List<Club> = emptyList(),
             onItemClicked: (Club) -> Unit) {
    val isSelected by remember { derivedStateOf { selectedClubs.contains(club) } }
}

@Composable
fun ClubItem(club: Club,
             selectedClubs: List<Club> = emptyList(),
             onItemClicked: (Club) -> Unit) {
    val isSelected by remember { mutableStateOf(selectedClubs.contains(club)) }
}

[Adam Powell]

what behavior are you looking to achieve?

[Adam Powell]

both of these snippets look suspicious and neither will do what you probably intend

[Adam Powell]

The first will create a derivedStateOf from the first value of selectedClubs the call to ClubItem is composed with and remember it, and if the selectedClubs list instance changes in a future recomposition, isSelected will always refer to the original list.

[Adam Powell]

That it's a derivedStateOf means that if that initial list happens to be a mutableStateListOf that changes over time, isSelected will update in response.

[Adam Powell]

The second also has the same problem where different list instances of selectedClubs will never update isSelected in a recomposition, since the initial composition instance is captured in the remember expression. val foo by remember { mutableStateOf(...) } should probably be a lint error.

[Adam Powell]

Overall, remember, DisposableEffect and LaunchedEffect can all result in lambda captures living longer than you expect and values going stale when you may or may not intend it.

[Adam Powell]

I suspect that what you want is probably:

val isSelected by rememberUpdatedState(club in selectedClubs)

if you're using isSelected in other observing or long-lived lambda captures later in the composable, or perhaps more simply:

val isSelected = club in selectedClubs

if you aren't.

[Shakil Karim]

Thanks for your detail answers, I'm using ClubItem in LazyClomn where each item can be selected and unselected and I'm maintaining this selected item in shared Preference like this
val selectedClubs = facrViewModel.savedClubs.collectAsState(initial = emptyList())

[Shakil Karim]

I initially tried to do something like this but it doesn't work.

@Composable
fun ClubItem(club: Club,
             isSelected: Boolean,
             onItemClicked: (Club) -> Unit) {
   }