Question

是否可以匹配通用案例类？我们的想法是使用一些通用案例类作为演员之间的消息。

多数民众赞成我的方法：无论如何都有可能实现这一目标吗？

case class EbTreeDataObject[T](uId: Long, changeId: Long, payload:Option[T])
case class InsertNewObject[T](newObject: EbTreeDataObject[T])
case class UpdateObject[T](changedObject: EbTreeDataObject[T])


class TreeActor[T](maxSynchroWait:Int,communication:CommunikationLayer[T]) extends Actor {
  var uIdTree = new EbTree[EbTreeDataObject[T]]
  var changeIdTree = new EbTree[EbTreeDataObject[T]]

  override def receive: Receive = {
    //basic tree operations
    case InsertNewObject(newObject: EbTreeDataObject[T]) =>
       //insert element in tree
    case UpdateObject(newObject: EbTreeDataObject[T]) =>
       //update object
    case RemoveObject(removedObject: EbTreeDataObject[T]) =>
       //remove object

这种结构在编译时会出错：

Error:(32, 37) pattern type is incompatible with expected type;
 found   : model.EbTreeDataObject[T]
 required: model.EbTreeDataObject[Any]
Note: T <: Any, but class EbTreeDataObject is invariant in type T.
You may wish to define T as +T instead. (SLS 4.5)
    case InsertNewObject(newObject: EbTreeDataObject[T]) =>

感谢您的帮助

Answer 1

为什么不做编译器建议的事情：

  case class EbTreeDataObject[+T](uId: Long, changeId: Long, payload: Option[T])

Scala：与通用案例类匹配的模式

1 个答案: