MVP-Rx-Kotlin

Contract.kt

sealed class PresenterToViewMsg
data class Msg1(val prop: Int): PresenterToViewMsg()
data class Msg2(val prop: String): PresenterToViewMsg()

sealed class ViewToPresenterMsg
data class Msg3(val prop: Int): ViewToPresenterMsg()
data class Msg4(val prop: String): ViewToPresenterMsg()

Presenter.kt

class Presenter {
  val messages = PublishSubject.create<PresenterToViewMsg>() as Observable<PresenterToViewMsg>
  
  fun onViewReady(view) {
    view.messages.subscribe {
       when(it) {
         is Msg3 -> messages.onNext(Msg1(4))
         is Msg4 -> messages.onNext(Msg2("Test"))
       }
    }
  }
}

View.kt

class MyActivity: AppCompatActivity {
  val messages = PublishSubject.create<ViewToPresenterMsg>() as Observable<PresenterToViewMsg>
  
  val presenter = Presenter()
  
  onStart() {
    presenter.messages.subscribe {
      when(it) {
         is Msg1 -> tv_1.visibility = View.VISIBLE
         is Msg2 -> tv_1.visibility = VIEW.GONE
      }
    }
    presenter.onViewReady(this)
  }
}