observablemap.scala

来自「JAVA 语言的函数式编程扩展」· SCALA 代码 · 共 59 行

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2006, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |                                         **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

// $Id: ObservableMap.scala 11911 2007-06-05 15:57:59Z odersky $


package scala.collection.mutable


/** This class is typically used as a mixin. It adds a subscription
 *  mechanism to the <code>Map</code> class into which this abstract
 *  class is mixed in. Class <code>ObservableMap</code> publishes
 *  events of the type <code>Message</code>.
 *
 *  @author  Matthias Zenger
 *  @author  Martin Odersky
 *  @version 2.0, 31/12/2006
 */
trait ObservableMap[A, B, This <: ObservableMap[A, B, This]] 
      extends Map[A, B]
      with Publisher[Message[(A, B)]
      with Undoable, This]
{ self: This =>

  abstract override def update(key: A, value: B): Unit = get(key) match {
    case None =>
      super.update(key, value)
      publish(new Include((key, value)) with Undoable {
        def undo = -=(key)
      })
    case Some(old) =>
      super.update(key, value)
      publish(new Update((key, value)) with Undoable {
        def undo = update(key, old)
      })
  }

  abstract override def -= (key: A): Unit = get(key) match {
    case None =>
    case Some(old) =>
      super.-=(key)
      publish(new Remove((key, old)) with Undoable {
        def undo = update(key, old)
      })
  }

  abstract override def clear(): Unit = {
    super.clear
    publish(new Reset with Undoable { 
      def undo: Unit = throw new UnsupportedOperationException("cannot undo") 
    })
  }
}