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我在 Play 应用程序中从 Slick 1.0 升级到 Slick 2.0 时遇到问题。

在我的应用程序中，我有一些用户定义的类型示例：

sealed trait UserStatus

case object NewUser extends UserStatus
case object ActiveUser extends UserStatus
case object BlockedUser extends UserStatus

object UserStatus extends SerializableEnum[UserStatus] {
  def mapping = Map[String, UserStatus](
    "NEW" -> NewUser,
    "ACTIVE" -> ActiveUser,
    "BLOCKED" -> BlockedUser
  )
}

和 slick 1.0 的通用映射器：

trait SerializableEnum[T] {
  def mapping: Map[String, T]

  def reverseMapping = mapping.map(_.swap)

  implicit def enumWrites = new Writes[T] {
    def writes(o: T): JsValue = JsString(reverseMapping(o))
  }

  implicit val enumReads = new Reads[T] {
    def reads(json: JsValue): JsResult[T] = json match {
      case JsString(s) => JsSuccess(mapping(s))
      case _ => JsError("Enum type should be of proper type")
    }
  }
  implicit val enumTypeMapper = MappedTypeMapper.base[T, String](reverseMapping, mapping)
}

迁移到 Slick 2.0 后，新的映射器不起作用：

trait SerializableEnum[T] {
  def mapping: Map[String, T]

  def reverseMapping:Map[T,String] = mapping.map(_.swap)

  implicit def enumWrites = new Writes[T] {
    def writes(o: T): JsValue = JsString(reverseMapping(o))
  }

  implicit val enumReads = new Reads[T] {
    def reads(json: JsValue): JsResult[T] = json match {
      case JsString(s) => JsSuccess(mapping(s))
      case _ => JsError("Enum type should be of proper type")
    }
  }
  implicit val enumTypeMapper = MappedColumnType.base[T, String](reverseMapping, mapping)
}

编译器说：

No ClassTag available for T

无法为 trait 定义 ClassTag 类型。有人知道如何解决吗？

我为此准备了示例应用程序： https ://github.com/mgosk/slick-test

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