painless-dagger-viewmodel.kt

class MainFragmentViewModel @Inject constructor(myService: MyService) : ViewModel() {

    private val data: MutableLiveData<String> = MutableLiveData()

    init {
        // call async service with callback
        myService.getData(data::setValue)
    }

    fun getData(): LiveData<String> = data
}

class MyService @Inject constructor() {
    // do something async and respond via callback. Could be RX, Coroutine or ExecutorService
    fun getData(onComplete: (String) -> Unit) {
        return onComplete("Hello From the Future")
    }
}