Question

是否可以在case类构造函数中编写其他不可用的属性？

case class Task(var name:String, var counter:Int) extends Entity

通过实体案例类扩展也有id属性

implicit val task = (
    (__ \ 'name).write[String] and
    (__ \ 'counter).write[Int] and
    (__ \ 'id).write[String] <==== ???
)(unlift(Task.unapply))

如何添加此属性？

Answer 1

您可以像这样定义您的写作：

implicit val writer = new Writes[Task] {
  def writes(t: Task): JsValue = {
    Json.obj("name" -> t.name,
      "counter" -> t.counter,
      "id" -> t.getIdFromSomewhere) //here's the thing you want
  }
}

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