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Scala example source code file (ObservableSet.scala)

This example Scala source code file (ObservableSet.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Scala tags/keywords

a, a, include, observableset, observableset, pub, publisher, remove, set, undoable, undoable, unit, unit, unsupportedoperationexception

The Scala ObservableSet.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |                                         **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */



package scala.collection
package mutable

import script._

/** This class is typically used as a mixin. It adds a subscription
 *  mechanism to the `Set` class into which this abstract
 *  class is mixed in. Class `ObservableSet` publishes
 *  events of the type `Message`.
 *
 *  @author  Matthias Zenger
 *  @version 1.0, 08/07/2003
 *  @since   1
 */
trait ObservableSet[A] extends Set[A] with Publisher[Message[A] with Undoable]
{ 

  type Pub <: ObservableSet[A]

  abstract override def +=(elem: A): this.type = {
    if (!contains(elem)) {
      super.+=(elem)
      publish(new Include(elem) with Undoable { def undo = -=(elem) })
    }
    this
  }

  abstract override def -=(elem: A): this.type = {
    if (contains(elem)) {
      super.-=(elem)
      publish(new Remove(elem) with Undoable { def undo = +=(elem) })
    }
    this
  }

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

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