Could not catch ClassCastException in scala

You cannot catch the Exception because you cannot use T. The JVM does not know T at runtime, so you have to trick it a bit ;-). Go implicit m: CLassManifest[T]

to your method and use m.erasure.cast(x)

. Yours might look like this:

abstract class Property

object EmptyProperty extends Property

class PropertyCompanion[T]

object Type extends PropertyCompanion[Type]
case class Type extends Property

object Name extends PropertyCompanion[Name]
case class Name extends Property

abstract class Entity {
  protected val properties: Map[PropertyCompanion[_], Property]
  def retrieve[T](key: PropertyCompanion[T])(implicit m: ClassManifest[T]) =
    properties.get(key) match {
      case Some(x) => x match {
        case EmptyProperty => throw new Exception("empty property")
        case _ => {
          try {
            m.erasure.cast(x).asInstanceOf[T]
          } catch {
            case e => throw new Exception("fubar")
          }
        }
      }
      case None => throw new Exception("not found")
    }
}

case class Book(protected val properties: Map[PropertyCompanion[_], Property]) extends Entity {
  def getType = retrieve(Type)
  def getName = retrieve(Name)
}

object Test extends App {

  val book = Book(Map(Type -> Type(), Name -> Type()))
  val name = book.getName
}

      

        
        
        
      

    

edit: added listing to T to get the correct return type