Android: Repositoryパターン RetrofitやRoomとの接続を分離して保守性UP

class UserViewModel (private val repository: UserRepository) : ViewModel() {

    val users: LiveData<List<User>> = repository.users.asLiveData()

    fun refreshUsers() {
        val users: LiveData<List<User>> = repository.asLiveData()

        fun refreshUsers() {
            viewModelScope.launch {
                repository.fetchUsersFromApi()
            }
        }
    }
}

class UserRepository(
    private val apiService: ApiService,
    private val userDao: UserDao
) {
    val users: Flow<List<User>> = userDao.getAllUsers()

    suspend fun fetchUsersFromApi() {
        try {
            val usersFromApi = apiService.getUsers()
            userDao.insertUsers(usersFromApi)
        } catch(e: Exception) {
            // error handling
        }
    }
}

class UserRepository(
    private val apiService: ApiService,
    private val userDao: UserDao
) {
    val users: Flow<List<User>> = userDao.getAllUsers()

    suspend fun fetchUsersFromApi() {
        try {
            val usersFromApi = apiService.getUsers()
            userDao.insertUsers(usersFromApi)
        } catch(e: Exception) {
            // error handling
        }
    }
}