PostsRepository.kt

fun getAllPosts() = flow<State<List<Post>>> {

    // Emit loading state
    emit(State.loading())

    val snapshot = mPostsCollection.get().await()
    val posts = snapshot.toObjects(Post::class.java)

    // Emit success state with data
    emit(State.success(posts))

}.catch {
    // If exception is thrown, emit failed state along with message.
    emit(State.failed(it.message.toString()))
}.flowOn(Dispatchers.IO)