如果我有这样的特征:
trait MyTrait[T] {
def myVal: T
}
然后我有一个案例类,例如:
case class MyClass(val foo: Int, val myVal: Boolean) extends MyTrait[Boolean]
最后,我还有另一个案例类
case class MyOtherClass(val bar: MyTrait[_])
如何将最后一个类序列化和反序列化为 Json?
我为 myClass 进行了如下读取和写入:
object MyClass {
implicit def MyClassWrites(implicit fmt: MyClass): Writes[MyClass] = new Writes[MyClass] {
override def writes(m: MyClass) = Json.obj(
"foo" -> m.foo,
"myVal" -> m.myVal // myVal should be Boolean
)
}
implicit def MyClassReads(implicit fmt: Reads[MyClass]): Reads[MyClass] = new Reads[MyClass] {
override def reads(json: JsValue): MyClass = new MyClass(
(json "foo").as[Int],
true
)
}
}
myOtherClass 还具有读取和写入功能,如下所示:
object MyOtherClass {
implicit def MyOtherClassWrites(implicit fmt: MyOtherClass): Writes[MyOtherClass] = new Writes[MyOtherClass] {
override def writes(m: MyOtherClass) = Json.obj(
"bar" -> Json.toJson(m.bar)
)
}
implicit def MyOtherClassReads(implicit fmt: Reads[MyOtherClass]): Reads[MyOtherClass] = new Reads[MyOtherClass] {
override def reads(json: JsValue): MyClass = new MyOtherClass(
(json "bar").as[MyClass[Boolean]]
)
}
}
编译时,出现以下错误:
Error:(43, 28) No Json serializer found for type A$A135.this.MyTrait[_$1]. Try to implement an implicit Writes or Format for this type.
"bar" -> Json.toJson(m.bar)
^
如果我将写入特征如下:
object MyTrait {
implicit def MyClassWrites(implicit fmt: MyTrait[_]): Writes[MyTrait[_]] = new Writes[MyTrait[_]] {
override def writes(m: MyTrait[_]) = Json.obj(
"myVal" -> Json.toJson(m.myVal) // myVal should be Boolean
)
}
implicit def MyClassReads(implicit fmt: Reads[MyTrait[_]]): Reads[MyTrait[_]] = new Reads[MyTrait[_]] {
override def reads(json: JsValue): MyTrait[_] = new MyClass(2, false)
}
}
我现在收到此错误:
Error:(10, 30) No Json serializer found for type _$4. Try to implement an implicit Writes or Format for this type.
"myVal" -> Json.toJson(m.myVal) // myVal should be Boolean
^
我在这里迷路了,有没有办法将酒吧序列化为好像它是 MyClass 一样?
I'vr还尝试更改MyTrait的编写器,如下所示:
override def writes(m: MyTrait[_]) = {
m match {
case c: MyClass => Json.toJson(c)
}
}
现在特征的编写器编译了,但我们回到第一个错误:
Error:(45, 28) No Json serializer found for type A$A199.this.MyTrait[_$9]. Try to implement an implicit Writes or Format for this type.
"bar" -> Json.toJson(m.bar)
^
我不明白,我已经定义了作家和读者,不是吗?
提前谢谢。
尝试定义以下实例。
implicit def MyTRead[T](implicit r: Reads[T]): Reads[MyTrait[T]] = ???
implicit def MyTWrite[T](implicit r: Writes[T]): Writes[MyTrait[T]] = ???