This library is created on an idea of Fabio Collini ( https://proandroiddev.com/unidirectional-data-flow-using-coroutines-f5a792bf34e5 ).
ViewStateStore
ViewStateStore wraps a LiveData for deliver ViewStates to the UI.
Supported ViewState types are;
- Success holds the real data
- Error holds and error ( which could be a custom class ) with its Throwable and an optiona customMessageRes.
- Loading
- None ( default initial value )
Installation
ViewStateStore
implementation( "studio.forface.viewstatestore:viewstatestore:last_version" )
Paging extension
implementation( "studio.forface.viewstatestore:viewstatestore-paging:last_version" )
Minimal usage
Create
class CarsViewModel(val getCars: GetCars): ViewModel() {
val cars = ViewStateStore<List<Car>>()
init {
cars.setLoading()
viewModelScope.launch {
runCatching { withContext(IO) { getCars() } }
.onSuccess { cars::set(it) }
.onFailure { cars.setError(it) }
}
}
}Get
observe ( with LifecycleOwner )
class CarsFragment: Fragment(), ViewStateFragment {
override fun onActivityCreated(savedInstanceState: Bundle?) {
// carsViewModel.cars.observeData { cars -> ... }
carsViewModel.cars.observe {
doOnData(::updateCars)
doOnError(::showError)
doOnLoading { isLoading -> progressBar.isVisible = isLoading }
}
}
}Iterator ( with CoroutineScope )
class CarsFragment: Fragment(), ViewStateFragment {
override fun onActivityCreated(savedInstanceState: Bundle?) {
lifecycleScope.launch {
// for (viewState in carsViewModel.cars) { ... }
// for (cars in carsViewModel.cars.data) { ... }
for ((onData, onError, onLoadingChange) in carsViewModel.cars.composed) {
onData?let(::updateCars)
onError?.let(::showError)
onLoadingChange?let { isLoading -> progressBar.isVisible = isLoading }
}
}
}
}await ( with CoroutineScope )
class CarsFragment: Fragment(), ViewStateFragment {
override fun onActivityCreated(savedInstanceState: Bundle?) {
lifecycleScope.launch {
val currentOrNextViewState = carsViewModel.cars.await()
val currentOrNextData = carsViewModel.cars.awaitData()
val onlyNextViewState = carsViewModel.cars.awaitNext()
val onlyNextData = carsViewModel.cars.awaitNextData()
}
}
}get ( nullable )
class CarsFragment: Fragment(), ViewStateFragment {
override fun onActivityCreated(savedInstanceState: Bundle?) {
val nullableCurrentViewState = carsViewModel.cars.state()
val nullableCurrentData = carsViewModel.cars.data()
try {
val currentViewState = carsViewModel.cars.unsafeState()
val currentData = carsViewModel.cars.unsafeData()
} catch(e: KotlinNullPointerException) {
...
}
}
}You can set also an ErrorResolution
// CarsViewModel
init {
loadCars()
}
private fun loadCars() {
cars.setLoading()
viewModelScope.launch {
runCatching { withContext(IO) { getCars() } }
.onSuccess(cars::setData)
.onFailure { cars.setError(it, ::loadCars) }
}
}
}
// CarsFragment
override fun onActivityCreated( savedInstanceState: Bundle? ) {
carsViewModel.cars.observe {
...
doOnError(::showError)
}
}
fun showError(error: ViewState.Error) {
Snackbar.make(
coordinatorLayout,
error.getMessage(requireContext()),
Snackbar.LENGTH_SHORT
).apply {
if (error.hasResolution())
setAction("Retry") { error.resolve() } }
show()
}
}
}It's also possible to lock the ViewStateStore for make it be mutable only from a ViewStateStoreScope
class CarsViewModel( val getCars: GetCars ): ViewModel(), ViewStateStoreScope {
val cars = ViewStateStore<List<Car>>().lock // Locking the ViewStateStore
}
class CarsFragment: Fragment(), ViewStateFragment {
override fun onActivityCreated( savedInstanceState: Bundle? ) {
carsViewModel.cars.postLoading() // Does NOT compile, LockedViewStateStore.postLoading not resolved
}
}From external source
A ViewStateStore can also be created from a LiveData or a DataSource.Factory ( see paging artifact for last one ).
val carsLiveData: LiveData<Car> = roomDatabase.getCars()
val cars = ViewStateStore.from( carsLiveData )val carsDataSource: DataSource.Factory<Int, Car> = roomDatabase.getCars()
val cars = ViewStateStore.from( carsDataSource )