Thing.kt

class MovieRepository @Inject
constructor(var apiService: ApiService) {

    fun fetchDiscoverMovies(page: Int): LiveData<Resource<DiscoverMovieResponse>> {
        return LiveDataReactiveStreams.fromPublisher(
            apiService.fetchDiscoverMovie(page) // returns Flowable<DiscoverMovieResponse>
                .subscribeOn(Schedulers.io())
                .map { d: DiscoverMovieResponse -> Resource.success(d) }
                .onErrorReturn { e -> Resource.error(e.message, null) }
        )
    }
}

class MainViewModel @Inject
constructor(private val movieRepository: MovieRepository) : ViewModel() {

    var discoverMovieLiveData: MediatorLiveData<Resource<DiscoverMovieResponse>> = MediatorLiveData()

    fun observeDiscoverMovie(): LiveData<Resource<DiscoverMovieResponse>> {
        return discoverMovieLiveData
    }

    fun fetchDiscoverMovies(page: Int) {
        val source = movieRepository.fetchDiscoverMovies(page)
        discoverMovieLiveData.addSource(source, Observer {
            discoverMovieLiveData.value = it
            discoverMovieLiveData.removeSource(source)
        })
    }

}