class UserActivity : AppCompatActivity() {

   //.....
   val presenter = UserPresenter()

   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)

      // Activity doesn't need to know how presenter works
      // for fetching data, it just know how to call the functions
      // So, if you add method inside presenter, it won't break the UI.
      // even the UI doesn't call the method.

      presenter.getUserData()
   }

   //....
}