scala.ref.WeakReference.scala Maven / Gradle / Ivy
/*
* Scala (https://www.scala-lang.org)
*
* Copyright EPFL and Lightbend, Inc.
*
* Licensed under Apache License 2.0
* (http://www.apache.org/licenses/LICENSE-2.0).
*
* See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*/
package scala.ref
/**
* A wrapper class for java.lang.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.
*/
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): WeakReference[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] = Option(wr.underlying.get)
}
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]