what does this error means? ```Reading a state that was created after the snapshot was taken or in a...

# compose

[Marko Novakovic]

what does this error means?

Reading a state that was created after the snapshot was taken or in a snapshot that has not yet been applied

[cb]

Paste the full stack trace? This kind of stuff can happen if you’re using mismatched library versions.

[Marko Novakovic]

@cb I made clone of JetNews for practise. This happens when I click on Home drawer item when Home is already selected

[Marko Novakovic]

E/AndroidRuntime: FATAL EXCEPTION: DefaultDispatcher-worker-1
    Process: com.marko.myjetnews, PID: 6766
    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:1521)
        at androidx.compose.runtime.snapshots.SnapshotKt.current(Snapshot.kt:1697)
        at androidx.compose.runtime.SnapshotMutableState.setValue(MutableState.kt:326)
        at com.marko.myjetnews.home.HomeViewModel.setPosts(HomeViewModel.kt:39)
        at com.marko.myjetnews.home.HomeViewModel.access$setPosts(Unknown Source:0)
        at com.marko.myjetnews.home.HomeViewModel$1.invokeSuspend(HomeViewModel.kt:33)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
        at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:106)
        at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:571)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:738)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:678)
        at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:665)

[Marko Novakovic]

in this code there is link to where error occurs

var posts by savedStateHandle.mutableStateOf<List<Post>>(
        key = SAVED_POSTS,
        initialState = emptyList(),
        save = { bundleOf(SAVED_POSTS to it) },
        restore = { it.getParcelableArrayList<Post>(SAVED_POSTS) ?: emptyList() },
    )
        private set

[Marko Novakovic]

fun <T> SavedStateHandle.mutableStateOf(
    key: String,
    initialState: T,
    save: (T) -> Bundle,
    restore: (Bundle) -> T,
): MutableState<T> {
    val bundle: Bundle? = get(key)
    val initial = if (bundle == null) initialState else restore(bundle)
    val state = mutableStateOf(initial)
    setSavedStateProvider(key) { save(state.value) }
    return state
}

[Chuck Jazdzewski [G]]

This error indicates that an instance created by mutableStateOf was read before snapshot it was created in was applied. This is most-likely caused by creating a muttableStateOf in composition and capturing it in a lambda invoked outside composition (such as in a coroutine).

My guess, from the stacks, is a coroutine that (probably indirectly) captured the posts field of HomeViewModel was started before the composition that create the view model was applied. Consider using LaunchEffect to start the coroutine instead as it waits until the composition applies successfully to start the coroutine avoiding such issues. Alternately, you can create the view model outside composition and pass it in as a parameter. All mutableStateOf created outside a snapshot (such as taken during composition) are automatically applied before any other snapshot is taken.

[Marko Novakovic]

Thanks @Chuck Jazdzewski [G]