Android LiveData ViewModel (Kotlin/Dagger)

HelloViewModel.kt

internal class HelloViewModel @Inject constructor(private val dataSource: Hello) : ViewModel() {

    // observed by ViewModel as a trigger to retrieve data from the source
    private var liveEndpoint: MutableLiveData<String> = MutableLiveData()

    // observed by Activity/Fragment or some other class as a trigger to do something with the data
    private var liveData: LiveData<String>

    init {
        // default observable endpoint
        liveEndpoint.value = dataSource.text

        // observe endpoint and reload observable liveData when endpoint changes
        liveData = Transformations.switchMap(liveEndpoint) {
            dataSource.fetchData(liveEndpoint.value!!)
        }
    }

    // trigger the observable endpoint to retrieve data
    fun setData(value: String) {
        liveEndpoint.value = value
    }

    // retrieve the observable data
    fun getData(): LiveData<String> = liveData
}

data class Hello(var text: String = "Hello World!!!") {
    private val liveData = MutableLiveData<String>()

    fun fetchData(value: String): LiveData<String> {
        liveData.value = value
        return liveData
    }
}

HelloViewModelActivity.kt

class HelloViewModelActivity : DaggerAppCompatActivity() {
    @Inject lateinit var hello: Hello
    @Inject lateinit var factory: ViewModelProvider.Factory

    private val viewModel by lazy(LazyThreadSafetyMode.NONE) {
        ViewModelProviders.of(this, factory).get(HelloViewModel::class.java)
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_hello)
        initializeViews()
        viewModel.getData().observe(this, Observer {
            it?.let { data -> updateUI(data) }
        })
    }

    private fun updateUI(data: String) {
        textHello.text = data
    }

    private fun initializeViews() {
        textHello.text = hello.text
        buttonHello.setOnClickListener {
            val text = editHello.text.toString()
            if (!text.isEmpty())
                viewModel.setData(text)
        }
    }
}