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Standard library for the Scala Programming Language
/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2006-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.ref
/**
* A wrapper class for java.lag.ref.WeakReference
* The new functionality is (1) results are Option values, instead of using null.
* (2) There is an extractor that maps the weak reference itself into an option.
* @author Sean McDirmid
*/
class WeakReference[+T <: AnyRef](value: T, queue: ReferenceQueue[T]) extends ReferenceWrapper[T] {
def this(value: T) = this(value, null)
val underlying: java.lang.ref.WeakReference[_ <: T] =
new WeakReferenceWithWrapper[T](value, queue, this)
}
/** An extractor for weak reference values */
object WeakReference {
/** Creates a weak reference pointing to `value` */
def apply[T <: AnyRef](value: T) = new WeakReference(value)
/** Optionally returns the referenced value, or `None` if that value no longer exists */
def unapply[T <: AnyRef](wr: WeakReference[T]): Option[T] = {
val x = wr.underlying.get
if (x != null) Some(x) else None
}
}
/**
* @author Philipp Haller
*/
private class WeakReferenceWithWrapper[T <: AnyRef](value: T, queue: ReferenceQueue[T], val wrapper: WeakReference[T])
extends java.lang.ref.WeakReference[T](value, if (queue == null) null else queue.underlying.asInstanceOf[java.lang.ref.ReferenceQueue[T]]) with ReferenceWithWrapper[T]