How to implement different kinds of return to the same query using Room and Android Rx?

Question

I'm facing this problem. Im using room to create the local database of my app. Let's say i have an Entity call User and a UserDao. It looks like this:

@Dao
interface UserDao: BaseDao<User>{
    @Query("SELECT * FROM user WHERE remote_id = :remoteId")
    fun getUser(remoteId : Long) : Single<User>
}

Nothing weird in this point, but what i want to do is be able to Changue the type of return in these functions. I want this because sometimes i need to get a Single but in other cases i need to get a Flowable. In this two cases the query is the same an the only thing than chagues is the type of return and i don't want to do something like this.

@Dao
interface UserDao: BaseDao<User>{

    @Query("SELECT * FROM user WHERE remote_id = :remoteId")
    fun getUserSingle(remoteId : Long) : Single<User>

    @Query("SELECT * FROM user WHERE remote_id = :remoteId")
    fun getUserFlowable(remoteId : Long) : Flowable<User>
 }

Any idea how to do this in a clean way?

karandeep singh · Accepted Answer · 2018-03-16T14:39:24.307

1

You can just use your Single<User> and call toFlowable() on it. Something like getUserSingle().toFlowable() on your dao object.

EDIT

You can us flowable operator and call it something like getUserFlowable.firstOrError() . because from the documentation

Returns a Single that emits only the very first item emitted by this Flowable or signals a {@link NoSuchElementException} if this Flowable is empty

edited Mar 16 '18 at 14:39

answered Mar 02 '18 at 20:56

karandeep singh

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But if i do that, any kind of update is never gonna be update it. Or am i wrong? with that method, it is gonna retrieve any kind of update in the user table? – Jhon Fredy Trujillo Ortega Mar 02 '18 at 21:37
1

how about using the flowable operator and call it something like `getUserFlowable.firstOrError()`? because from the documentations > Returns a Single that emits only the very first item emitted by this Flowable or signals a {@link NoSuchElementException} if this Flowable is empty. – karandeep singh Mar 03 '18 at 06:47
Yeah it sounds better, i din't find these method at reading, tnx for the coment :D. im gonna see how it works – Jhon Fredy Trujillo Ortega Mar 03 '18 at 16:20
Let me know if this works. I'll edit my answer then. – karandeep singh Mar 03 '18 at 17:46
I keep looking for a better way, using generics types, but room is very restricted to generic code, so your answe is the best. So, create an answer plz :D – Jhon Fredy Trujillo Ortega Mar 15 '18 at 20:08

How to implement different kinds of return to the same query using Room and Android Rx?

1 Answers1