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How to implement loadstate with adapter, recyclerView?

I would like to implement a feature like loadStateFlow in Paging 3.
I do not use pagination in my implementation and it is not necessary in my case.
Could I make it another way?
I have found something like LoadingStateAdapter library
https://developer.android.com/reference/kotlin/androidx/paging/LoadStateAdapter
For now I get a list using method in the fragment:
private fun collectNotificationItems() {
vm.notificationData.collectWith(viewLifecycleOwner) {
notificationAdapter.items = it
}
}
This is implementation I would like to achieve, example is in paging3:
private fun collectItems() {
vm.items.collectWith(viewLifecycleOwner, adapter::submitData)
adapter.loadStateFlow.collectWith(viewLifecycleOwner) { loadState ->
vm.setLoadingState(loadState.refresh is LoadState.Loading)
val isEmpty =
loadState.source.refresh is LoadState.NotLoading && loadState.append.endOfPaginationReached && archiveAdapter.itemCount < 1
vm.setEmptyStateVisible(isEmpty)
}
}
Where methods are:
in ViewModel
fun setLoadingState(isLoading: Boolean) {
_areShimmersVisible.value = isLoading && !_isSwipingToRefresh.value
if (!isLoading) _isSwipingToRefresh.value = false
}
areShimmers and isSwiping are MutableStateFlow
Could you recommend any other options?
EDIT:
I have the whole implementation a little bit different.
I have use case to make it
class GetListItemDetailsUseCase #Inject constructor(private val dao: Dao): BaseFlowUseCase<Unit, List<ItemData>>() {
override fun create(params: Unit): Flow<List<ItemData>> {
return flow{
emit(dao.readAllData())
}
}
}
For now it looks like the code above.
How to use DateState in that case?
EDIT2:
class GetNotificationListItemDetailsUseCase #Inject constructor(private val notificationDao: NotificationDao): BaseFlowUseCase<Unit, DataState<List<NotificationItemsResponse.NotificationItemData>>>() {
override fun create(params: Unit): Flow<DataState<List<NotificationItemsResponse.NotificationItemData>>> {
return flow{
emit(DataState.Loading)
try {
emit(DataState.Success(notificationDao.readAllDataState()))
} catch(e: Exception) {
emit(DataState.Error(e)) // error, and send the exception
}
}
}
}
DAO
#Query("SELECT * FROM notification_list ORDER BY id ASC")
abstract suspend fun readAllDataState(): DataState<List<NotificationItemsResponse.NotificationItemData>>
/\ error beacause of it:
error: Not sure how to convert a Cursor to this method's return type
fragment
private suspend fun collectNotificationItems() {
vm.notificationData.collectLatest { dataState ->
when(dataState) {
is DataState.Error -> {
collectErrorState()
Log.d("collectNotificationItems", "Collect ErrorState")
}
DataState.Loading -> {
Log.d("collectNotificationItems", "Collect Loading")
}
is DataState.Success<*> -> {
vm.notificationData.collectWith(viewLifecycleOwner) {
notificationAdapter.items = it
notificationAdapter.notifyDataSetChanged()
Log.d("collectNotificationItems", "Collect Sucess")
}
}
}
}

You could use a utility class (usually called DataState or something like that).
sealed class DataState<out T> {
data class Success<out T>(val data: T) : DataState<T>()
data class Error(val exception: Exception) : DataState<Nothing>()
object Loading : DataState<Nothing>()
}
Then, you change your flow's return type from Flow<YourObject> to Flow<DataState<YourObject>> and emit the DataStates within a flow {} or channelFlow {} block.
val notificationsFlow: Flow<DataState<YourObject>> get() = flow {
emit(DataState.Loading) // when you collect, you will receive this DataState telling you that it's loading
try {
// networking/database stuff
emit(DataState.Success(yourResultObject))
} catch(e: Exception) {
emit(DataState.Error(e)) // error, and send the exception
}
}
Finally, just change your collect {} to be like:
notificationsFlow.collectLatest { dataState ->
when(dataState) {
is DataState.Error -> { } // error occurred, deal with it here
DataState.Loading -> { } // it's loading, show progress bar or something
is DataState.Success -> { } // data received from the flow, access it with dataState.data
}
}
For more information on this regard, check this out.

How to propagate the response of an async operation to the view using Jetpack Compose?

I have this sealed class:
sealed class Resource<out T> {
object Loading: Resource<Nothing>()
data class Success<out T>(val data: T): Resource<T>()
data class Failure(val message: String): Resource<Nothing>()
}
In the repository class I have this function that deletes an item from an API:
override suspend fun deleteItem(id: String) = flow {
try {
emit(Resource.Loading)
emit(Resource.Success(itemsRef.document(id).delete().await()))
} catch (e: Exception) {
emit(Resource.Failure(e.message))
}
}
The result of the delete operation is Void?. Now, in the ViewModel class I declare:
val state = mutableStateOf<Resource<Void?>>(Success(null))
And update it when the delete completes:
fun deleteItem(id: String) {
viewModelScope.launch {
repo.deleteItem(id).collect { response ->
state.value = response
}
}
}
I have created a Card and inside onClick I have added:
IconButton(
onClick = viewModel.deleteItem(id),
)
Which actually deletes that item form database correctly. But I cannot track the result of the operation. I tried using:
when(val res = viewModel.state.value) {
is Resource.Loading -> Log.d(TAG, "Loading")
is Resource.Success -> Log.d(TAG, "Success")
is Resource.Failure -> Log.d(TAG, "Failure")
}
But only the case Loading is triggered. No success/failure at all. What can be wrong here? As it really acts like a synchronous operation.

I've tested your approach without a repository, and compose part looks totally fine:
var i = 0
#Composable
fun TestScreen(viewModel: TestViewModel = viewModel()) {
val state by viewModel.state
Text(
when (val stateSmartCast = state) {
is Resource.Failure -> "Failure ${stateSmartCast.message}"
Resource.Loading -> "Loading"
is Resource.Success -> "Success ${stateSmartCast.data}"
}
)
Button(onClick = {
viewModel.deleteItem(++i)
}) {
}
}
class TestViewModel : ViewModel() {
val state = mutableStateOf<Resource<Int>>(Resource.Success(i))
fun deleteItem(id: Int) {
viewModelScope.launch {
deleteItemInternal(id).collect { response ->
state.value = response
}
}
}
suspend fun deleteItemInternal(id: Int) = flow {
try {
emit(Resource.Loading)
delay(1000)
if (id % 3 == 0) {
throw IllegalStateException("error on third")
}
emit(Resource.Success(id))
} catch (e: Exception) {
emit(Resource.Failure(e.message ?: e.toString()))
}
}
}
So the the problem looks like in this line itemsRef.document(id).delete().await()), or in your connection to the repository.

Try collecting in the composable function:
val state = viewModel.state.collectAsState()
Then you can do: when (val res = viewModel.state.value){...}.
However I am sceptical about the deleteItem in the repository returning a flow. Do you really need such thing? You can always map stuff in the viewModel.

Android: Firebase Object is null when using kotlin flow

My problem is, that when I try to get a document out of my database, that this document aka the object is always null. I only have this problem when I use Kotlin Coroutines to get the document out of my database. Using the standard approach with listeners do work.
EmailRepository
interface EmailRepository {
suspend fun getCalibratePrice(): Flow<EmailEntity?>
suspend fun getRepairPrice(): Flow<EmailEntity?>
}
EmailRepository Implementation
class EmailRepositoryImpl #Inject constructor(private val db: FirebaseFirestore) : EmailRepository {
fun hasInternet(): Boolean {
return true
}
// This works! When using flow to write a document, the document is written!
override fun sendEmail(email: Email)= flow {
emit(EmailStatus.loading())
if (hasInternet()) {
db.collection("emails").add(email).await()
emit(EmailStatus.success(Unit))
} else {
emit(EmailStatus.failed<Unit>("No Email connection"))
}
}.catch {
emit(EmailStatus.failed(it.message.toString()))
}.flowOn(Dispatchers.Main)
// This does not work! "EmailEntity" is always null. I checked the document path!
override suspend fun getCalibratePrice(): Flow<EmailEntity?> = flow {
val result = db.collection("emailprice").document("Kalibrieren").get().await()
emit(result.toObject<EmailEntity>())
}.catch {
}.flowOn(Dispatchers.Main)
// This does not work! "EmailEntity" is always null. I checked the document path!
override suspend fun getRepairPrice(): Flow<EmailEntity?> = flow {
val result = db.collection("emailprice").document("Reparieren").get().await()
emit(result.toObject<EmailEntity>())
}.catch {
}.flowOn(Dispatchers.Main)
}
Viewmodel where I get the data
init {
viewModelScope.launch {
withContext(Dispatchers.IO) {
if (subject.value != null){
when(subject.value) {
"Test" -> {
emailRepository.getCalibratePrice().collect {
emailEntity.value = it
}
}
"Toast" -> {
emailRepository.getRepairPrice().collect {
emailEntity.value = it
}
}
}
}
}
}
}
private val emailEntity = MutableLiveData<EmailEntity?>()
private val _subject = MutableLiveData<String>()
val subject: LiveData<String> get() = _subject
Fragment
#AndroidEntryPoint
class CalibrateRepairMessageFragment() : EmailFragment<FragmentCalibrateRepairMessageBinding>(
R.layout.fragment_calibrate_repair_message,
) {
// Get current toolbar Title and send it to the next fragment.
private val toolbarText: CharSequence by lazy { toolbar_title.text }
override val viewModel: EmailViewModel by navGraphViewModels(R.id.nav_send_email) { defaultViewModelProviderFactory }
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
// Here I set the data from the MutableLiveData "subject". I don't know how to do it better
viewModel.setSubject(toolbarText.toString())
}
}
One would say, that the Firebase rules are the problems here, but that should not be the case here, because the database is open and using the listener approach does work.
I get the subject.value from my CalibrateRepairMessageFragment. When I don't check if(subject.value != null) I get a NullPointerException from my init block.
I will use the emailEntitiy only in my viewModel and not outside it.
I appreciate every help, thank you.
EDIT
This is the new way I get the data. The object is still null! I've also added Timber.d messages in my suspend functions which also never get executed therefore flow never throws an error.. With this new approach I don't get a NullPointerException anymore
private val emailEntity = liveData {
when(subject.value) {
"Test" -> emailRepository.getCalibratePrice().collect {
emit(it)
}
"Toast" -> emailRepository.getRepairPrice().collect {
emit(it)
}
// Else block is never executed, therefore "subject.value" is either Test or toast and the logic works. Still error when using flow!
else -> EmailEntity("ERROR", 0F)
}
}
I check if the emailEntity is null or not with Timber.d("EmailEntity is ${emailEntity.value}") in one of my functions.
I then set the price with val price = MutableLiveData(emailEntity.value?.basePrice ?: 1000F) but because emailentity is null the price is always 1000
EDIT 2
I have now further researched the problem and made a big step forward. When observing the emailEntity from a fragment like CalibrateRepairMessageFragment the value is no longer null.
Furthermore, when observing emailEntity the value is also not null in viewModel, but only when it is observed in one fragment! So how can I observe emailEntity from my viewModel or get the value from my repository and use it in my viewmodel?

Okay, I have solved my problem, this is the final solution:
Status class
sealed class Status<out T> {
data class Success<out T>(val data: T) : Status<T>()
class Loading<T> : Status<T>()
data class Failure<out T>(val message: String?) : Status<T>()
companion object {
fun <T> success(data: T) = Success<T>(data)
fun <T> loading() = Loading<T>()
fun <T> failed(message: String?) = Failure<T>(message)
}
}
EmailRepository
interface EmailRepository {
fun sendEmail(email: Email): Flow<Status<Unit>>
suspend fun getCalibratePrice(): Flow<Status<CalibrateRepairPricing?>>
suspend fun getRepairPrice(): Flow<Status<CalibrateRepairPricing?>>
}
EmailRepositoryImpl
class EmailRepositoryImpl (private val db: FirebaseFirestore) : EmailRepository {
fun hasInternet(): Boolean {
return true
}
override fun sendEmail(email: Email)= flow {
Timber.d("Executed Send Email Repository")
emit(Status.loading())
if (hasInternet()) {
db.collection("emails").add(email).await()
emit(Status.success(Unit))
} else {
emit(Status.failed<Unit>("No Internet connection"))
}
}.catch {
emit(Status.failed(it.message.toString()))
}.flowOn(Dispatchers.Main)
// Sends status and object to viewModel
override suspend fun getCalibratePrice(): Flow<Status<CalibrateRepairPricing?>> = flow {
emit(Status.loading())
val entity = db.collection("emailprice").document("Kalibrieren").get().await().toObject<CalibrateRepairPricing>()
emit(Status.success(entity))
}.catch {
Timber.d("Error on getCalibrate Price")
emit(Status.failed(it.message.toString()))
}
// Sends status and object to viewModel
override suspend fun getRepairPrice(): Flow<Status<CalibrateRepairPricing?>> = flow {
emit(Status.loading())
val entity = db.collection("emailprice").document("Kalibrieren").get().await().toObject<CalibrateRepairPricing>()
emit(Status.success(entity))
}.catch {
Timber.d("Error on getRepairPrice")
emit(Status.failed(it.message.toString()))
}
}
ViewModel
private lateinit var calibrateRepairPrice: CalibrateRepairPricing
private val _calirateRepairPriceErrorState = MutableLiveData<Status<Unit>>()
val calibrateRepairPriceErrorState: LiveData<Status<Unit>> get() = _calirateRepairPriceErrorState
init {
viewModelScope.launch {
when(_subject.value.toString()) {
"Toast" -> emailRepository.getCalibratePrice().collect {
when(it) {
is Status.Success -> {
calibrateRepairPrice = it.data!!
_calirateRepairPriceErrorState.postValue(Status.success(Unit))
}
is Status.Loading -> _calirateRepairPriceErrorState.postValue(Status.loading())
is Status.Failure -> _calirateRepairPriceErrorState.postValue(Status.failed(it.message))
}
}
else -> emailRepository.getRepairPrice().collect {
when(it) {
is Status.Success -> {
calibrateRepairPrice = it.data!!
_calirateRepairPriceErrorState.postValue(Status.success(Unit))
}
is Status.Loading -> _calirateRepairPriceErrorState.postValue(Status.loading())
is Status.Failure -> _calirateRepairPriceErrorState.postValue(Status.failed(it.message))
}
}
}
price.postValue(calibrateRepairPrice.head!!.basePrice)
}
}
You can now observe the status in one of your fragments (but you dont need to!)
Fragment
viewModel.calibrateRepairPriceErrorState.observe(viewLifecycleOwner) { status ->
when(status) {
is Status.Success -> requireContext().toast("Price successfully loaded")
is Status.Loading -> requireContext().toast("Price is loading")
is Status.Failure -> requireContext().toast("Error, Price could not be loaded")
}
}
This is my toast extensions function:
fun Context.toast(text: String, duration: Int = Toast.LENGTH_SHORT) {
Toast.makeText(this, text, duration).show()
}

NetworkBoundResource with Kotlin coroutines

Do you have any ideas how to implement repository pattern with NetworkBoundResource and Kotlin coroutines? I know we can launch a coroutine withing a GlobalScope, but it may lead to coroutine leak. I would like to pass a viewModelScope as a parameter, but it is a bit tricky, when it comes to implementation (because my repository doesn't know a CoroutineScope of any ViewModel).
abstract class NetworkBoundResource<ResultType, RequestType>
#MainThread constructor(
private val coroutineScope: CoroutineScope
) {
private val result = MediatorLiveData<Resource<ResultType>>()
init {
result.value = Resource.loading(null)
#Suppress("LeakingThis")
val dbSource = loadFromDb()
result.addSource(dbSource) { data ->
result.removeSource(dbSource)
if (shouldFetch(data)) {
fetchFromNetwork(dbSource)
} else {
result.addSource(dbSource) { newData ->
setValue(Resource.success(newData))
}
}
}
}
#MainThread
private fun setValue(newValue: Resource<ResultType>) {
if (result.value != newValue) {
result.value = newValue
}
}
private fun fetchFromNetwork(dbSource: LiveData<ResultType>) {
val apiResponse = createCall()
result.addSource(dbSource) { newData ->
setValue(Resource.loading(newData))
}
result.addSource(apiResponse) { response ->
result.removeSource(apiResponse)
result.removeSource(dbSource)
when (response) {
is ApiSuccessResponse -> {
coroutineScope.launch(Dispatchers.IO) {
saveCallResult(processResponse(response))
withContext(Dispatchers.Main) {
result.addSource(loadFromDb()) { newData ->
setValue(Resource.success(newData))
}
}
}
}
is ApiEmptyResponse -> {
coroutineScope.launch(Dispatchers.Main) {
result.addSource(loadFromDb()) { newData ->
setValue(Resource.success(newData))
}
}
}
is ApiErrorResponse -> {
onFetchFailed()
result.addSource(dbSource) { newData ->
setValue(Resource.error(response.errorMessage, newData))
}
}
}
}
}
}

Update (2020-05-27):
A way which is more idiomatic to the Kotlin language than my previous examples, uses the Flow APIs, and borrows from Juan's answer can be represented as a standalone function like the following:
inline fun <ResultType, RequestType> networkBoundResource(
crossinline query: () -> Flow<ResultType>,
crossinline fetch: suspend () -> RequestType,
crossinline saveFetchResult: suspend (RequestType) -> Unit,
crossinline onFetchFailed: (Throwable) -> Unit = { Unit },
crossinline shouldFetch: (ResultType) -> Boolean = { true }
) = flow<Resource<ResultType>> {
emit(Resource.Loading(null))
val data = query().first()
val flow = if (shouldFetch(data)) {
emit(Resource.Loading(data))
try {
saveFetchResult(fetch())
query().map { Resource.Success(it) }
} catch (throwable: Throwable) {
onFetchFailed(throwable)
query().map { Resource.Error(throwable, it) }
}
} else {
query().map { Resource.Success(it) }
}
emitAll(flow)
}
The above code can be called from a class, e.g. a Repository, like so:
fun getItems(request: MyRequest): Flow<Resource<List<MyItem>>> {
return networkBoundResource(
query = { dao.queryAll() },
fetch = { retrofitService.getItems(request) },
saveFetchResult = { items -> dao.insert(items) }
)
}
Original answer:
This is how I've been doing it using the livedata-ktx artifact; no need to pass in any CoroutineScope. The class also uses just one type instead of two (e.g. ResultType/RequestType) since I always end up using an adapter elsewhere for mapping those.
import androidx.lifecycle.LiveData
import androidx.lifecycle.liveData
import androidx.lifecycle.map
import nihk.core.Resource
// Adapted from: https://developer.android.com/topic/libraries/architecture/coroutines
abstract class NetworkBoundResource<T> {
fun asLiveData() = liveData<Resource<T>> {
emit(Resource.Loading(null))
if (shouldFetch(query())) {
val disposable = emitSource(queryObservable().map { Resource.Loading(it) })
try {
val fetchedData = fetch()
// Stop the previous emission to avoid dispatching the saveCallResult as `Resource.Loading`.
disposable.dispose()
saveFetchResult(fetchedData)
// Re-establish the emission as `Resource.Success`.
emitSource(queryObservable().map { Resource.Success(it) })
} catch (e: Exception) {
onFetchFailed(e)
emitSource(queryObservable().map { Resource.Error(e, it) })
}
} else {
emitSource(queryObservable().map { Resource.Success(it) })
}
}
abstract suspend fun query(): T
abstract fun queryObservable(): LiveData<T>
abstract suspend fun fetch(): T
abstract suspend fun saveFetchResult(data: T)
open fun onFetchFailed(exception: Exception) = Unit
open fun shouldFetch(data: T) = true
}
Like #CommonsWare said in the comments, however, it'd be nicer to just expose a Flow<T>. Here's what I've tried coming up with to do that. Note that I haven't used this code in production, so buyer beware.
import kotlinx.coroutines.flow.*
import nihk.core.Resource
abstract class NetworkBoundResource<T> {
fun asFlow(): Flow<Resource<T>> = flow {
val flow = query()
.onStart { emit(Resource.Loading<T>(null)) }
.flatMapConcat { data ->
if (shouldFetch(data)) {
emit(Resource.Loading(data))
try {
saveFetchResult(fetch())
query().map { Resource.Success(it) }
} catch (throwable: Throwable) {
onFetchFailed(throwable)
query().map { Resource.Error(throwable, it) }
}
} else {
query().map { Resource.Success(it) }
}
}
emitAll(flow)
}
abstract fun query(): Flow<T>
abstract suspend fun fetch(): T
abstract suspend fun saveFetchResult(data: T)
open fun onFetchFailed(throwable: Throwable) = Unit
open fun shouldFetch(data: T) = true
}

#N1hk answer works right, this is just a different implementation that doesn't use the flatMapConcat operator (it is marked as FlowPreview at this moment)
#FlowPreview
#ExperimentalCoroutinesApi
abstract class NetworkBoundResource<ResultType, RequestType> {
fun asFlow() = flow {
emit(Resource.loading(null))
val dbValue = loadFromDb().first()
if (shouldFetch(dbValue)) {
emit(Resource.loading(dbValue))
when (val apiResponse = fetchFromNetwork()) {
is ApiSuccessResponse -> {
saveNetworkResult(processResponse(apiResponse))
emitAll(loadFromDb().map { Resource.success(it) })
}
is ApiErrorResponse -> {
onFetchFailed()
emitAll(loadFromDb().map { Resource.error(apiResponse.errorMessage, it) })
}
}
} else {
emitAll(loadFromDb().map { Resource.success(it) })
}
}
protected open fun onFetchFailed() {
// Implement in sub-classes to handle errors
}
#WorkerThread
protected open fun processResponse(response: ApiSuccessResponse<RequestType>) = response.body
#WorkerThread
protected abstract suspend fun saveNetworkResult(item: RequestType)
#MainThread
protected abstract fun shouldFetch(data: ResultType?): Boolean
#MainThread
protected abstract fun loadFromDb(): Flow<ResultType>
#MainThread
protected abstract suspend fun fetchFromNetwork(): ApiResponse<RequestType>
}

I am new to Kotlin Coroutine. I just come across this problem this week.
I think if you go with the repository pattern as mentioned in the post above, my opinion is feeling free to pass a CoroutineScope into the NetworkBoundResource. The CoroutineScope can be one of the parameters of the function in the Repository, which returns a LiveData, like:
suspend fun getData(scope: CoroutineScope): LiveDate<T>
Pass the build-in scope viewmodelscope as the CoroutineScope when calling getData() in your ViewModel, so NetworkBoundResource will work within the viewmodelscope and be bound with the Viewmodel's lifecycle. The coroutine in the NetworkBoundResource will be cancelled when ViewModel is dead, which would be a benefit.
To use the build-in scope viewmodelscope, don't forget add below in your build.gradle.
implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.2.0-alpha01'

Return custom object from onError() of Rx java Android instead of throw-able object

I am new to RX Java. While implementing Rx java with Retrofit i found i am getting throw-able object in my doOnError(){}
But what i want my doOnError() of RX Java should return ErrorBase() -> that is my custom class. instead of throwable.
it will help me to handle error at central. i will pass my throw-able object to my ErrorBase class where i have handled custom messages.
Below is doOnError(). Where i want to return ErrorBase object
apiInterface.getLoginDetails(auth)
.doOnNext {
//LoginResponse
}
doOnError{
return ErrorBase(throwable)
}
Code of other classes.
Api Interface class
interface ApiInterface {
#POST("login")
fun getLoginDetails(#Header(Constants.AUTHORIZATION) auth: String): Observable<LoginResponseModel>
}
LoginRepository
class LoginRepository #Inject constructor(private val apiInterface: ApiInterface,
val utils: Utils) {
fun getLoginDetails(auth: String): Observable<LoginResponseModel> {
return apiInterface.getLoginDetails(auth)
.doOnNext {
}
.doOnError {
//Right now having throw-able object
}
}
}
ErrorBase
class ErrorBase(private val throwable: Throwable) {
private var message: String?
private var statusCode: Int
init {
statusCode = getStatusCode()
message = getMessage()
}
private fun getStatusCode(): Int {
if (throwable is HttpException) {
val exception = throwable
return exception.code()
}
return -1
}
private fun getMessage() =
when (throwable) {
is IOException -> "Something Went Wrong"
is UnknownHostException -> "No internet connectivity"
is SocketTimeoutException -> "Slow Internet connectivity"
else -> throwable.message
}
}
LoginvViewModel
class LoginViewModel #Inject constructor(
private val loginRepository: LoginRepository) : ViewModel() {
private val TAG = this.javaClass.name
private var loginResult: MutableLiveData<LoginResponseModel> = MutableLiveData()
private var loginError: MutableLiveData<String> = MutableLiveData()
private var loginLoader: MutableLiveData<Boolean> = MutableLiveData()
private lateinit var disposableObserver: DisposableObserver<LoginResponseModel>
fun loginResult(): LiveData<LoginResponseModel> {
return loginResult
}
fun loginError(): LiveData<String> {
return loginError
}
fun loginLoader(): LiveData<Boolean> {
return loginLoader
}
private fun getLoginData(auth: String) {
loginLoader.postValue(true)
initLoginObserver()
loginRepository.getLoginDetails(auth)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.debounce(400, MILLISECONDS)
.subscribe(disposableObserver)
}
private fun initLoginObserver() {
disposableObserver = object : DisposableObserver<LoginResponseModel>() {
override fun onComplete() {
}
override fun onNext(loginDetails: LoginResponseModel) {
loginResult.postValue(loginDetails)
loginLoader.postValue(false)
}
override fun onError(e: Throwable) {
loginError.postValue(e.message)
loginLoader.postValue(false)
}
}
}
fun disposeElements() {
if (null != disposableObserver && !disposableObserver.isDisposed) disposableObserver.dispose()
}
fun loginClicked() {
getLoginData("auth")
}}

Firstly, doOnError isn't aimed to transform/return some data, but helps to handle side-effects like logging.
Second thing, ErrorBase doesn't fit well together with LoginResponseModel cause they don't have any common parent.
Thus, I suggest you following solution:
Create one base class for your response:
sealed class LoginResponse {
class Result( ..your data here.. ) : LoginResponse()
class Error( ... ) : LoginResponse()
}
Make function return LoginResponse and do following changes:
fun getLoginDetails(auth: String): Observable<LoginResponse> {
return apiInterface.getLoginDetails(auth)
.map { data -> LoginResponse.Result(data) }
.onErrorReturn { throwable -> LoginResponse.Error(throwable) }
}
Now both results have one common parent and you can use getLoginDetails in the following way:
fun doRequest() {
loginRepository.getLoginDetails(auth)
.subscribe { result ->
when (result) {
is LoginResponse.Result -> //do something with result
is LoginResponse.Error -> //do something with error
}
}
}
Some explanation.
onErrorReturn does exactly what you need - returns your custom value in case if error occurs
If you don't add LoginResponse you have to make Observable<Any> which is loosely typed and doesn't really well describes your interface.
Making LoginResponse sealed allows to check only 2 cases whether emitted data is Result or Error. Otherwise Kotlin compiler forces you to add additional else branch
Update In case if you need to do same thing in multiple places you can go with this:
sealed class Response<T> {
data class Result<T>(val result: T) : Response<T>()
data class Error<T>(val throwable: Throwable) : Response<T>()
}
fun getLoginDetails(auth: String): Observable<Response<LoginResponseModel>> {
return apiInterface.getLoginDetails(auth)
.map<Response<LoginResponseModel>> { data -> Response.Result(data) }
.onErrorReturn { throwable -> LoginResponse.Error(throwable) }
}
..and somewhere in your code..
fun handleResponse(response: Response<LoginData>) {
when (response) {
is Response.Result -> response.result
is Response.Error -> response.throwable
}
}