HandleEventsAndStateWithSharedFlowAndStateFlow

HandleEventsAndStateWithSharedFlowAndStateFlow.kt

// ViewModel with SharedFlow and StateFlow

abstract class BaseViewModel<STATE, EVENT : UiEvent, EFFECT : UiEffect>(
    initialState: UiState<STATE> = UiState.Loading
) : ViewModel() {
  
    ...

    // Get Current State
    val currentState: UiState<STATE>
        get() = uiState.value
  
    private val _uiState: MutableStateFlow<UiState<STATE>> = MutableStateFlow(initialState)
    val uiState = _uiState.asStateFlow()
    
    private val _event: MutableSharedFlow<EVENT> = MutableSharedFlow()
    val event = _event.asSharedFlow()
    
    protected fun setUiEvent(newEvent: EVENT) {
        viewModelScope.launch { _event.emit(newEvent) }
    }

    protected fun updateUiState(update: (UiState<STATE>) -> UiState<STATE>) {
        val newState = update(currentState)
        if (newState != currentState) {
            _uiState.value = newState
        }
    }

    abstract fun handleEvent(event: EVENT)

    ...
}


// And how to pass info to ViewModel to handle events and update state
abstract class BaseFragment<STATE, EVENT : UiEvent, EFFECT : UiEffect,
    VM : BaseViewModel<STATE, EVENT, EFFECT>, VDB : ViewDataBinding>(
    @LayoutRes private val layoutId: Int,
    vmKClass: KClass<VM>
) : Fragment() {

    ...

    @InternalCoroutinesApi
    final override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        with(viewModel) {
            event
                .onEach { handleEvent(it) }
                .observeInLifecycle(viewLifecycleOwner)

            uiState
                .onEach { handleState(it) }
                .observeInLifecycle(viewLifecycleOwner)
        }
    }

    ...
}