android viewmodel 에서 constructor arguments

AndroidViewModel을 상속받아 application을 사용하면 쉽다

ViewModel에서 context를 constructor argument로 받고 싶은 경우에는

ViewModelProvider.Factory를 상속받아 create를 구현하면 된다.

그런데 이렇게도 보통 사용을 할까?

class RoomViewModelFactory(private val helper: RoomMemoHelper) : ViewModelProvider.Factory {
    override fun <T : ViewModel> create(modelClass: Class<T>): T {
        return if (modelClass.isAssignableFrom(RoomViewModel::class.java)) {
            RoomViewModel(helper) as T
        } else {
            throw IllegalArgumentException()
        }
    }
}

class RoomViewModel(private val helper: RoomMemoHelper) : ViewModel() {

    private val dao: RoomMeoDao = helper.roomMeoDao()
    .........
}

private lateinit var helper: RoomMemoHelper
private lateinit var viewModel: RoomViewModel

override fun onCreate(savedInstanceState: Bundle?) {
  .....
  helper = Room.databaseBuilder(this, RoomMemoHelper::class.java, "room_db")
            .allowMainThreadQueries()//학습시만
            .build()
  viewModel = ViewModelProvider(this, RoomViewModelFactory(helper))[RoomViewModel::class.java]
}