@Composable
fun ListScreen(viewModel: ListViewModel, navController: NavController) {
    val viewState = viewModel.mState.observeAsState()
    when (val state = viewState.value) {
        is ListViewState.Init -> {
            Column() {
                repeat(state.list.size) {
                    TextField(value = state.list[it],
                        onValueChange = { str ->
                            viewModel.obtainEvent(ListEvent.NameChange(it,
                                str))
                        })
                }
            }
        }
    }
}

@HiltViewModel
class ListViewModel @Inject constructor() : ViewModel(), EventHandler<ListEvent> {
    private val m_state: MutableLiveData<ListViewState> =
        MutableLiveData(ListViewState.Init())
    val mState: LiveData<ListViewState> = m_state

    override fun obtainEvent(event: ListEvent) {
        when (val state = m_state.value) {
            is ListViewState.Init -> {
                reduce(state, event)
            }
        }
    }

    fun reduce(initState: ListViewState.Init, event: ListEvent) {
        when (event) {
            is ListEvent.NameChange -> {
                initState.list[event.index] = event.text
                m_state.postValue(initState)
            }
        }
    }
}