与Akka演员正确差异

Question

我在使用仿制药和akka演员时经常遇到以下问题：

trait AuctionParticipantActor[P <: AuctionParticipant[P]]
  extends StackableActor {

  override def receive: Receive = {
    case message: Handled =>
      participant = participant.handle(message)
      super.receive(message)
    case message =>
      super.receive(message)
  }
  protected var participant: P
}

AuctionParticipantActor只是周围AuctionParticipant周围的包装器。我需要P类型是协变量的，我不确定什么是实现这一目标的最佳方法。

另外，对于我的用例，我什至不需要参数化AuctionParticipantActor。我可以有类似的东西：

trait AuctionParticipantActor
  extends StackableActor {

  override def receive: Receive = {
    case message: Handled =>
      participant = participant.handle(message)
      super.receive(message)
    case message =>
      super.receive(message)
  }
  protected var participant: AuctionParticipant[???]
}

但是在这种情况下，我不确定该代替什么？？？为了尊重绑定的类型。如果有人认为我的问题与设计有关，请这样说。想法？

Answer 1

如果您不使用F-bond-bound-polymormorlism，为什么您需要AuctionParticipant才能通用？然后，AuctionParticipant[P]中类型参数P的含义是什么？如您所说，AuctionParticipantActor只是AuctionParticipant上的包装器，并且如果AuctionParticipantActor不再是通用的，那么也许AuctionParticipant也不应该是。

trait AuctionParticipantActor
  extends StackableActor {

  override def receive: Receive = {
    case message: Handled =>
      participant = participant.handle(message)
      super.receive(message)
    case message =>
      super.receive(message)
  }
  protected var participant: AuctionParticipant
}
trait AuctionParticipant {
  // ...
}

否则，如果AuctionParticipant仍然应该是通用的（即P还有其他含义），那么也许您可以使用存在类型：

trait AuctionParticipantActor
  extends StackableActor {

  override def receive: Receive = {
    case message: Handled =>
      participant = participant.handle(message)
      super.receive(message)
    case message =>
      super.receive(message)
  }
  protected var participant: AuctionParticipant[_]
}
trait AuctionParticipant[P] {
  // ...
}