斯卡拉.从特征引用复制案例类

Question

嗨，我正在尝试以"优雅"和类型安全的方式解决问题，但我找不到最好的......

假设我有这个特质

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案例类复制方法，而无需转换为 AEvent 或 BEvent...

由于我引用了该特征，我想出的最佳解决方案是创建这样的方法：

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]
}

我不喜欢的是有效负载类型是在运行时强制转换的......如何在编译时进行类型检查？

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]而不是AEvent？