Scala example source code file (Signallable.scala)

This example Scala source code file (Signallable.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

accesscontrolexception, none, option, security, sig, signallable, signallable, some, some, string, string, t, t

The Scala Signallable.scala source code

/* NSC -- new Scala compiler
 * Copyright 2005-2011 LAMP/EPFL
 * @author Paul Phillips
 */
 
package scala.tools
package util

import java.security.AccessControlException

/** A class for things which are signallable.
 */
abstract class Signallable[T] private (val signal: String, val description: String) {
  private var last: Option[T] = None
  private def lastString = last match {
    case Some(())   => ""
    case Some(x)    => "" + x
    case _          => ""
  }
  
  /** The most recent result from the signal handler. */
  def lastResult: Option[T] = last
  
  /** Method to be executed when the associated signal is received. */
  def onSignal(): T
  
  // todo:
  // def unregister(): Boolean
  
  override def toString =  "  SIG(%s) => %s%s".format(
    signal, description, if (lastString == "") "" else " (" + lastString + ")"
  )
}

object Signallable {
  /** Same as the other apply, but an open signal is found for you.
   */
  def apply[T](description: String)(body: => T): Signallable[T] = wrap {
    apply(SignalManager.findOpenSignal().name, description)(body)
  }
    
  /** Given a signal name, a description, and a handler body, this
   *  registers a signal handler and returns the Signallable instance.
   *  The signal handler registry is thereafter available by calling
   *  SignalManager.info(), or sending SIGINFO to the manager will
   *  dump it to console.
   */
  def apply[T](signal: String, description: String)(body: => T): Signallable[T] = wrap {
    val result = create[T](signal, description, body)
    SignalManager.public(signal, description)(result.onSignal())
    result
  }

  private def wrap[T](body: => Signallable[T]): Signallable[T] =
    try body catch { case _: AccessControlException => null }

  private def create[T](signal: String, description: String, body: => T): Signallable[T] =
    new Signallable[T](signal, description) {
      def onSignal = {
        val result = body
        last = Some(result)
        result
      }
    }
}