activity-viewstate.kt

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    setUpObservation()
}

private fun setUpObservation() {
    viewModel.viewState.observe(this, Observer { state ->
        when (state) {
            is ProfileViewModel.ViewState.ProfileLoaded -> {
                // render avatar, user name, photos etc.
                textViewName.text = state.profile.name
                // ...
            }
            is ProfileViewModel.ViewState.ProfileLoadFailure -> {
                // render error layout with icon, error messages
            }
            ProfileViewModel.ViewState.Loading -> {
                // render loading animation
            }
        }
    })
}