class Repository {
    // ....
    fun login(user:String, password:String): LiveData<Status> { /* ... */ }
}

class LoginViewModel : ViewModel() {

    @Inject
    lateinit var repo: Repository

    private var auth = MutableLiveData<User>()
    private var showErrorEvent = SingleLiveEvent<String>()
    private var showSuccessEvent = SingleLiveEvent<String>()

    private val authenticationStatus = Transformations.switchMap(auth, { data ->
        repo.login(data.user, data.password)
    })

    // Called from UI
    fun performLogin(data:Data){
        auth.value = data
    }

}