LiveData returns wrong Object

Question

I added Hilt to my project and now LiveData returns wrong Object type. Maybe I made some wrong changes in my code. getAllCurrencies returns LiveData<Resource<Unit>> but it should LiveData<Resource<Currencies>>

ViewModel:

class SplashScreenViewModel @ViewModelInject constructor(
private val roomDatabaseRepository: RoomDatabaseRepository,
private val retrofitRepository: RetrofitRepository) : ViewModel() {

fun getAllCurrencies(mainCurrency: String) = liveData(Dispatchers.IO) {
       emit(Resource.loading(data = null))
        try {
            emit(Resource.success(data = retrofitRepository.getAllCurrencies(mainCurrency)))
        } catch (exception: Exception) {
            emit(Resource.error(data = null, message = exception.message ?: "Error Occurred!"))
        }
    }

Repository: (It returns good type)

class RetrofitRepository @Inject constructor(val currenciesApiHelper: CurrenciesApiHelper) {

suspend fun getAllCurrencies(mainCurrency: String) {
  currenciesApiHelper.getAllCurrencies(mainCurrency)
}

Answer 1

You should return currenciesApiHelper.getAllCurrencies(mainCurrency) in to Repository.

---

(optional) Following is the way I do it with MVVM:

I'll assume that you have Currency as a model declared somewhere already.

Status

sealed class Status<out T> {
    class Loading<out T> : Status<T>()
    data class Success<out T>(val data: T) : Status<T>()
    data class Failure<out T>(val exception: Exception) : Status<T>()
}

Fragment/Presentation Layer

viewModel.fetchCurrencies(mainCurrency)
            .observe(viewLifecycleOwner, Observer { result ->
                when (result) {
                    is Status.Loading<*> -> {
                        //display a ProgressBar or so
                    }

                    is Status.Success<*> -> {
                        //Status.Success<*> can also be Status.Success<ArrayList<Currency>>
                        //hide the ProgressBar
                        val currencies = result.data as ArrayList<Currency> 
                    }

                    is Status.Failure<*> -> {
                        //log the exception
                    }
                }
            })

ViewModel

private val repo = Repository()

@ExperimentalCoroutinesApi
    fun fetchCurrencies(mainCurrency: String): LiveData<Status<MutableList<Currency>>> =
        liveData(Dispatchers.IO) {
            emit(Status.Loading())

            try {
                repo.getCurrencies(mainCurrency).collect {
                    emit(it)
                }

            } catch (e: Exception) {
                emit(Status.Failure(e))
                Log.e("ERROR:", e.message!!)
            }
        }

Repository (single datasource)

Using Firestore instead here as I'm not 100% certainly sure about your way.

Do what retrofitRepository.getAllCurrencies(mainCurrency) should do and then offer the result.

private val fs: FirebaseFirestore = Firebase.firestore

@ExperimentalCoroutinesApi
    fun getCurrencies(mainCurrency: String): Flow<Status<MutableList<Currency>>> = callbackFlow {

        val subscription = fs.collection("currencies")
            .addSnapshotListener { snapshot, _ ->
                if (snapshot != null) {
                    val result = snapshot.toObjects(Currency::class.java)
                    offer(Success(result))
                }
            }

        awaitClose { subscription.remove() }
    }

Using coroutines is by the way quite sweet. Have a look here:

Learn advanced coroutines with Kotlin Flow and LiveData

Android Coroutines: How to manage async tasks in Kotlin

Hope it helps :)