Room DAO keeps returning NULL

Question

In room, I have a dao to something like this:

@Dao
interface FacultyDao {
    @Query("select * from faculty")
    fun getAll(): LiveData<List<Faculty>>
  
    ...
}

And inside the repository, I'm simply calling this method and logging it:

class FacultyRepository(application: Application) {

    private val facultyDao: FacultyDao

    init {
        val db: AppDB = AppDB.getInstance(application)
        facultyDao = db.facultyDao()
    }

    fun getAllFaculty(): LiveData<List<Faculty>> {
        val v = facultyDao.getAll()
        Log.d("muaxx", v.value.toString())
        return v
    }
     ...

}

But the thing is it's returning me null, but when I ran that query in inspector it worked. Am I missing something?

Answer 1

Here is what I have done:

• creating instance of facultyRepository inside AndroidViewModel, like this: private val facultyRepository = FacultyRepository(application)
• also creating a variable (faculties) to store the result in some mutable livedata, like this: val faculties: MutableLiveData<List<Faculty>> = MutableLiveData(ArrayList())
• inside a method called init I'm observing the getAllFaculty using observeForever

And yes, I need to call this init method once, from the fragment.

Relevant code:

class FacultyListViewModel(application: Application) : AndroidViewModel(application) {
    private val facultyRepository = FacultyRepository(application)

    val faculties: MutableLiveData<List<Faculty>> = MutableLiveData(ArrayList())

    fun init() {
        facultyRepository.getAllFaculty().observeForever {
            faculties.postValue(it)
        }
    }
}

If you have got some better approach, feel free to suggest here.