如何编写特征的读取方法

Question

我有一个特征/案例类设置，如：

sealed trait Vehicle
case class Honda(...) extends Vehicle
case class Toyota(...) extends Vehicle

case class VehicleSet(bestSeller: Vehicle, others: Seq[Vehicle])

当我为VehicleSet写入读取时，它正在说

"No Json deserializer found for type Vehicle.  Try to implement an implicit reads or Format this type"
object VehicleJsonFormats {
  implicit val hondaWrites ...
  implicit val toyotaWrites ...
  implicit val vehicleSetWrites ...

  implicit val hondaReads ...
  implicit val tototaReads ...


  implicit val vehicleSetReads: Reads[VehicleSet] = (
    (JsPath \ "bestSeller").read[Vehicle] and
    (JsPath \ "other").read[Seq[Vehicle]]
  ) (VehicleSet.apply _)
}

我很困惑这会如何与Trait一起使用？

Answer 1

您需要Reads[Vehicle]之类的内容：

implicit val vehicleReads: Reads[Vehicle] = Reads[Vehicle] {
  case json: JsObject =>
    (json \ "make").asOpt[String] match {
      case Some("Honda") => hondaReads.reads(json)
      case Some("Toyota") => toyotaReads.reads(json)
      case _ => JsError("Vehicle expected")
    }
  case _ => JsError("JsObject expected")
}