IllegalStateException: Reading a state that was created after the snapshot was taken or in a snapshot that has not yet

Question

Assume simplfied class like:

class MyModel() { companion object val number = mutableStateOf(0) init { refresh() } fun refresh() { RestClient.getNumber() .doOnNext { i -> number.value = i } .take(1) .subscribe() } }

which I instantiate somewhere else:

val myModel = remember { MyModel() }

sometimes I get:

Caused by: java.lang.IllegalStateException: Reading a state that was created after the snapshot was taken or in a snapshot that has not yet been applied at androidx.compose.runtime.snapshots.SnapshotKt.readError(Snapshot.kt:1865) at androidx.compose.runtime.snapshots.SnapshotKt.current(Snapshot.kt:2171) at androidx.compose.runtime.SnapshotMutableStateImpl.setValue(SnapshotState.kt:299) at com.example.MyModel$refresh$4.accept(MyModel.kt:14)

How can I avoid mentioned IllegalStateException?

Akshay · Accepted Answer · 2024-04-04 06:03:51Z

The illegalStateException you are encountering is likely due to a concurrency issue, to avoid this issue, you should ensure that the state updates are performed in a way that is compatible with compose's lifecycle.

class MyModel : ViewModel() { val number by mutableStateOf(0) init { refresh() } fun refresh() { viewModelScope.launch(Dispatchers.IO) { val newNumber = RestClient.getNumber() // Update the state on the UI thread viewModelScope.launch(Dispatchers.Main) { number.value = newNumber } } } }

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