Generic type in MutableLiveData in kotlin

Question

I have a val _user: MutableLiveData<Resource<List<ApiUser>>> = MutableLiveData()in viewmodel but i want to postValue errorException

  // A generic class that contains data and status about loading this data.
    sealed class Resource<T>(
        val data: T? = null,
        val message: String? = null
    ) {
        class Success<T>(data: T) : Resource<T>(data)
        class Loading<T>(data: T? = null) : Resource<T>(data)
        class Error<T>(message: String, data: T? = null) : Resource<T>(data, message)
    }

//ViewModel

class HomeViewModel : ViewModel() {
    
        val _user: MutableLiveData<Resource<List<ApiUser>>> = MutableLiveData()
        var job: CompletableJob? = null
        fun f() {
            job = Job()
            _user.postValue(Resource.Loading(null))
            CoroutineScope(IO+job!!).launch {
                try {
                    _user.postValue(Resource.Success(RetrofitBuilder.apiService.getUsers()))
                } catch (e: Throwable) {
                    _user.postValue(Resource.Error("",e))
                }
            }
        }
     fun cancelJob() {
            job?.cancel()
        }
    
    }

//Fragment

fun subScribeUI() {
        viewModel!!._user.observe(viewLifecycleOwner, Observer {
            it?.let {
               when(it.status) {
                   Status.LOADING -> {
                       Timber.d("LOADING")
                   }
                   Status.SUCCESS -> {
                       Timber.d("SUCCESS")
                   }
                   Status.ERROR -> {
                       Timber.d("ERROR")
                   }
               }
            }
        })
    }

       override fun onDestroyView() {
        super.onDestroyView()
viewModel?.cancelJob()
    }

Why are you creating a new scope? You already have the `viewModelScope`. — EpicPandaForce, Aug 03 '20 at 13:40
That's not an answer, viewModelScope is also a coroutine scope — EpicPandaForce, Aug 03 '20 at 13:48
@EpicPandaForce you mean i shoud use viewModelScope.launch {} instead of CoroutineScope(IO+job!!).launch {}? — Mansukh Ahir, Aug 03 '20 at 14:03
I believe this is indeed what he meant. Using this, you also don't need to cancel the job in `onDestroy()` (or anywhere else), because `viewModelScope` is already bound to `viewModel`s lifecycle. — Primož Ivančič, Aug 03 '20 at 14:30

score 1 · Answer 1 · answered Aug 03 '20 at 14:36

1

The problem is that you are trying to assign e, which is of type Throwable to argument of type List<ApiUser>.

Instead of

_user.postValue(Resource.Error("", e))

you need to do this:

_user.postValue(Resource.Error(errorMessage, emptyList())

or

_user.postValue(Resource.Error(errorMessage, null)

where errorMessage is e.message or something similar.

answered Aug 03 '20 at 14:36

Primož Ivančič

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Thanks for the answer, but in UI how can i know the reason about error? If it's timeout or other network issue. – Mansukh Ahir Aug 03 '20 at 17:22
Add another parameter to `Resource`, to make it `Resource`. This way, you can pass in `Throwable` (or anything else) as well. – Primož Ivančič Aug 03 '20 at 17:59

Generic type in MutableLiveData in kotlin

1 Answers1