The state of MVI on Android - Roxie - NoteListViewModel

Roxie-NoteListViewModel.kt

class NoteListViewModel(
    initialState: State?,
    private val loadNoteListUseCase: GetNoteListUseCase
) : CoroutineViewModel<Action, State>() {
    override val initialState = initialState ?: State(isIdle = true)
    private val reducer: Reducer<State, Change> = { state, change ->
        when (change) {
            is Change.Loading -> state.copy(
                isIdle = false,
                isLoading = true,
                notes = emptyList(),
                isError = false
            )
            is Change.Notes -> state.copy(
                isLoading = false,
                notes = change.notes
            )
            is Change.Error -> state.copy(
                isLoading = false,
                isError = true
            )
        }
    }
    init {
        bindActions()
    }
    private fun bindActions() {
        val loadNotesChange: Flow<Change> = actions.asFlow()
            .ofType<Action.LoadNotes>()
            .flatMapLatest {
                loadNoteListUseCase.loadAll()
                    .flowOn(Dispatchers.IO)
                    .map { Change.Notes(it) }
                    .defaultOnEmpty(Change.Notes(emptyList()))
                    .catch<Change> {
                        emit(Change.Error(it))
                    }
                    .onStart { emit(Change.Loading) }
            }
        // to handle multiple Changes, use Observable.merge to merge them into a single stream:
        // val allChanges = Observable.merge(loadNotesChange, ...)
        loadNotesChange
            .scan(initialState) { state, change ->
                reducer.invoke(state, change)
            }
            .filter { !it.isIdle }
            .distinctUntilChanged()
            .flowOn(Dispatchers.Main)
            .observeState()
            .catch {
                Timber.e(it)
            }
            .launchHere()
    }
}