Scala example source code file (DelayedLazyVal.scala)

This example Scala source code file (DelayedLazyVal.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

concurrent, delayedlazyval, executioncontext, runnable, t, unit

The DelayedLazyVal.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala.concurrent


/** A `DelayedLazyVal` is a wrapper for lengthy computations which have a
 *  valid partially computed result.
 *
 *  The first argument is a function for obtaining the result at any given
 *  point in time, and the second is the lengthy computation.  Once the
 *  computation is complete, the `apply` method will stop recalculating it
 *  and return a fixed value from that point forward.
 *
 *  @param  f      the function to obtain the current value at any point in time
 *  @param  body   the computation to run to completion in another thread
 *
 *  @author  Paul Phillips
 *  @version 2.8
 */
class DelayedLazyVal[T](f: () => T, body: => Unit)(implicit exec: ExecutionContext){
  @volatile private[this] var _isDone = false
  private[this] lazy val complete = f()

  /** Whether the computation is complete.
   *
   *  @return true if the computation is complete.
   */
  def isDone = _isDone

  /** The current result of f(), or the final result if complete.
   *
   *  @return the current value
   */
  def apply(): T = if (isDone) complete else f()

  exec.execute(new Runnable { def run = { body; _isDone = true } })
}