PostRepo.kt

interface PostRepository {
    fun fetchFeeds(): Completable
    fun getFeeds(): Observable<List<Post>>
}

class PostRepositoryImpl : PostRepository {

    private val remoteDataSource: PostApiService by inject()
    private val localDataSource: PostDao by inject()

    override fun fetchFeeds(): Completable {
        return remoteDataSource.fetchFeeds()
            .flatMapObservable {
                if (it.isSuccessful)
                    Observable.fromIterable(it.body())
                else
                    throw HttpException(it)
            }.concatMapCompletable {
                Completable.fromAction {
                    localDataSource.upsert(it)
                }
            }
    }

    override fun getFeeds(): Observable<List<Post>> {
        return localDataSource.getPostList()
    }
}