// interface for view/activity/fragment/whatever, can be delegated also.

interface LoginAcceptable {
    fun onChangeLocation()
    fun onLoginSuccess()
    fun onAppUpdateAvailable()
    fun renderLocationConfig(configuration: LocationConfiguration)
}


// alias for short name in single livedata
typealias LoginEvent = LoginAcceptable.() -> Unit



// single livedata in view model
val ui = MutableLiveData<LoginEvent>()



// just syntax sugar
operator fun <T> MutableLiveData<T>.invoke(function: T) {
    postValue(function)
}



// viewmodel function
fun onLogin() {

    // call to this single livedata
    ui {
        onLoginSuccess()
        onAppUpdateAvailable()
    }
}


// observe in your view
viewModel.ui.observe { it(this) }