Scala example source code file (PropImpl.scala)

This example Scala source code file (PropImpl.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

collection, creatorimpl, none, option, prop, propimpl, some, string, t, t1, unit

The PropImpl.scala Scala example source code

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

package scala
package sys

import scala.collection.mutable

/** The internal implementation of scala.sys.Prop.
 */
private[sys] class PropImpl[+T](val key: String, valueFn: String => T) extends Prop[T] {
  def value: T = if (isSet) valueFn(get) else zero
  def isSet    = underlying contains key
  def set(newValue: String): String = {
    val old = if (isSet) get else null
    underlying(key) = newValue
    old
  }
  def setValue[T1 >: T](newValue: T1): T = {
    val old = value
    if (newValue == null) set(null)
    else set("" + newValue)
    old
  }
  def get: String =
    if (isSet) underlying.getOrElse(key, "")
    else ""

  def clear(): Unit = underlying -= key
  def option: Option[T] = if (isSet) Some(value) else None
  def or[T1 >: T](alt: => T1): T1 = if (isSet) value else alt

  /** The underlying property map, in our case always sys.props */
  protected def underlying: mutable.Map[String, String] = scala.sys.props
  protected def zero: T = null.asInstanceOf[T]
  private def getString = if (isSet) "currently: " + get else "unset"
  override def toString = "%s (%s)".format(key, getString)
}

private[sys] abstract class CreatorImpl[+T](f: String => T) extends Prop.Creator[T] {
  def apply(key: String): Prop[T] = new PropImpl[T](key, f)
}