Question

您好，我试图通过优雅的方式来解决问题＆＃34;并输入安全的方式，但我找不到最好的......

让我说我有这个特质

trait Event {
  def deviceId: String
  def userId: String
  def eventDateTime: DateTime
  def payload: Option[Payload]
}

trait Payload

以下案例类（可能还有更多）

case class AEvent (deviceId: String, userId: String, eventDateTime: DateTime, payload: Option[APayload]) extends Event
case class APayload (content: String)


case class BEvent (deviceId: String, userId: String, eventDateTime: DateTime, payload: Option[BPayload]) extends Event
case class BPayload (size: Int, name: String)

我想直接从特征中使用case类复制方法而不会转换为AEvent或BEvent ......

由于我提到了特征，我想出的最佳解决方案是创建一个这样的方法：

def copy[T <: Event](event: T)(deviceId: String = event.deviceId,
                             userId: String = event.userId,
                             eventDateTime: DateTime = event.eventDateTime,
                             payload: Option[Payload] = event.payload) T = {
  val res = event match {
    case x: AEvent => AEvent(deviceId, userId, eventDateTime, payload.asInstanceOf[APayload])
    case x: BEvent => BEvent(deviceId, userId, eventDateTime, payload.asInstanceOf[BPayload])
  }
res.asInstanceOf[T]
}

我不喜欢的是Payload类型是在运行时输入的...... 如何在编译期间进行类型检查？

提前致谢

Answer 1

怎么样？

case class Event[P <: Payload](deviceId: String, userId: String, eventDateTime: DateTime, payload: Option[P])

并使用Event[APayload]代替AEvent？

斯卡拉。来自特征参考的案例类副本

1 个答案: