斯卡拉反射

final class Key[T]

object Registry {
   private var backingMap: Map[Key[_],_] = Map.empty

   def put[T](k: Key[T],v: T) = backingMap += (k -> v)

   def get[T](k: Key[T]): Option[T] = backingMap get k map (_.asInstanceOf[T])
}

scala> val strKey = new Key[String] 
strKey: Key[String] = Key@31028a

scala> val intKey = new Key[Int]
intKey: Key[Int] = Key@7ae77ca4

scala> Registry.put(strKey,"asdf")

scala> Registry.get(strKey)
res0: Option[String] = Some(asdf)

scala> Registry.put(intKey,"asdf")
<console>:10: error: type mismatch;
 found   : Key[Int]
 required: Key[Any]
       Registry.put(intKey,"asdf")

或者,您可以使用无类型键并使用清单将类型信息存储在Map中(如Daniel suggested)：

class Registry[K] {
   import scala.reflect.Manifest

   private var _map= Map.empty[K,(Manifest[_],Any)] 

   def put[T](key: K,item: T)(implicit m: Manifest[T]) {
      _map += (key -> (m,item))
   }

   def get[T](key:K)(implicit m : Manifest[T]): Option[T] = {
      for ((om,v) <- _map get key if om <:< m) 
         yield v.asInstanceOf[T]
   }
}

后一种方法的优点是您可以将任何东西用作键,而不必传递原始类型的键对象.但是,它的缺点是,在调用get方法时必须指定值类型.如果你指定了错误的类型,你将获得None,就好像密钥根本不在注册表中一样,而对于键入的键,你可以保证获得与密钥相关的任何值.