Android Room with RxJava handle empty query result

Question

Trying to test new Android Room librarty with RxJava adapter. And I want to handle result if my query returns 0 objects from DB:

So here is DAO method:

@Query("SELECT * FROM auth_info")
fun getAuthInfo(): Flowable<AuthResponse>

And how I handle it:

database.authDao()
    .getAuthInfo()
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .switchIfEmpty { Log.d(TAG, "IS EMPTY") }
    .firstOrError()
    .subscribe(
            { authResponse -> Log.d(TAG, authResponse.token) },
            { error -> Log.d(TAG, error.message) })

My DB is empty, so I expect .switchIfEmty() to work, but none of handling methods is firing. Neither .subscribe() nor .switchIfEmpty()

Answer 1

Db Flowables are observable (so they keep dispatching if database changes) so it never completes. You can try returning List<AuthResponse>. We've considered back porting an optional but decided not to do it, at least for now. Instead, we'll probably add support for Optional in different known libraries.

Answer 2

In version 1.0.0-alpha5, room added support of Maybe and Single to DAOs, so now you can write something like

@Query("SELECT * FROM auth_info")
fun getAuthInfo(): Maybe<AuthResponse>

You can read more about it here