Room + Kotlin Flow not emitting result

Question

i'm trying to fetch some data from api, and them store on room database, so the main data source is roomDatabase.

my repository code looks like:

 suspend fun fetchData(): Flow<Response<List<Foo>>> {
            val shouldRequestData = dao.getFoo().isEmpty()
            return if (shouldRequestData) {
                getFoo()
            } else getLocalFoo()
        }
    
        override suspend fun getFoo(): Flow<Response<List<Foo>>> {
    
            return ....... request done normally... inserting normally on database (and showing 
on database inspector)
        }
    
        override suspend fun getLocalFoo(): Flow<Response<List<Foo>>> = flow {
            dao.getFoo().transform<List<FooLocal>, Response<List<Foo>>> {
               Response.Success(
                   it.map {
                     it.toDomainModel()
                   }
               )
    }
}

on Dao:

 @Query("SELECT * FROM localdb")
    fun getFoo(): Flow<List<Foo>>

and then collecting it normally on viewmodel...

The problem is: the data is not appearing.. how could i solve this? The non-flow version works :/ I already searched for this problem, but nothing seems to work.

score 0 · Answer 1 · answered May 14 '21 at 20:40

Solved by putting this on getLocalFoo() ->

val result: Flow<Response<List<Foo>>> = 
     Transformations.map(dao.getFoo()) {
            Response.Success(it?.map {
                it.asDomainModel()
            } ?: emptyList()
        }.asFlow()

return result

score 0 · Answer 2 · answered Jan 30 '23 at 08:57

I have found a solution to investing so much time.

Solution: Same Dao Object should be used when we insert details into the room database and get information from DB.

If you are using dagger hilt then

@Singleton annotation will work.

I hope this will solve your problem.

Room + Kotlin Flow not emitting result

2 Answers2