dolphins-sample.kt

data class ChatState(
  val messages: List<Message> = emptyList(),
  val input: String = ""
)

sealed class ChatMutation {
  data class NewMessage(val message: Message) : ChatMutation()
  data class NewInput(val input: String) : ChatMutation()
  object SendMessage : ChatMutation()
}

sealed class ChatEffect {
  data class SendMessage(val text: String) : ChatEffect()
  object SubscribeToChat : ChatEffect()
}

fun ChatState.update(mutation: ChatMutation): Pair<ChatState, Set<ChatEffect>> =
  when (mutation) {
    is ChatMutation.NewMessage -> copy(messages = messages + mutation.message) to emptySet()
    is ChatMutation.NewInput -> copy(input = mutation.input) to emptySet()
    is ChatMutation.SendMessage -> copy(input = "") to setOf(ChatEffect.SendMessage(input))
  }

val feature = RxFeature(
  ChatState(),
  setOf(ChatEffect.SubscribeToChat),
  ChatState::update,
  acquireChatHandler() // omitted, will be covered later
)

feature.rxState()
  .observeOn(mainThread())
  .subscribe { state ->
    render(state)
  }

textField.setInputListener { newText -> feature.mutate(ChatMutation.NewInput(newText)) }
sendButton.setOnClickListener { feature.mutate(ChatMutation.SendMessage) }