bookings.kt

// `BookingsActivity` is rotatable and currently loads bookings from API on each rotation. How can we prevent this from happening? 
class BookingViewModel(
    private val repository: BookingsRepository
) : ViewModel() {

    // We want to make sure that this is only settable privately.
    val bookings = MutableLiveData<List<Booking>>()

    fun loadBookings() {
        val bookings = repository.getBookings()
        bookings.postValue(bookings)
    }
}


class BookingsActivity : AppCompatActivity() {

    lateinit var bookingViewModelFactory: BookingViewModelFactory

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val viewModel = ViewModelProviders.of(this, bookingViewModelFactory).get(BookingViewModel::class.java)

        viewModel.bookings.observe(this, Observer {
            // Update UI with list of bookings
        }) 
        viewModel.loadBookings()
    }
}