scala.ref.WeakReference

class WeakReference[+T <: AnyRef] extends ReferenceWrapper[T]

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.

Value Members From scala.Proxy

def equals(that: Any): Boolean

Compares the receiver object ( this ) with the argument object ( that ) for equivalence.

Any implementation of this method should be an equivalence relation :

  • It is reflexive: for any instance x of type Any , x.equals(x) should return true .
  • It is symmetric: for any instances x and y of type Any , x.equals(y) should return true if and only if y.equals(x) returns true .
  • It is transitive: for any instances x , y , and z of type Any if x.equals(y) returns true and y.equals(z) returns true , then x.equals(z) should return true .

If you override this method, you should verify that your implementation remains an equivalence relation. Additionally, when overriding this method it is usually necessary to override hashCode to ensure that objects which are “equal” ( o1.equals(o2) returns true ) hash to the same scala.Int. ( o1.hashCode.equals(o2.hashCode) ).

  • that
    • the object to compare against this object for equality.
  • returns
    • true if the receiver object is equivalent to the argument; false otherwise.
  • Definition Classes
    • Proxy → Any

(defined at scala.Proxy)

Instance Constructors From scala.ref.WeakReference

new WeakReference(value: T)

(defined at scala.ref.WeakReference)

Full Source:

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2006-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */


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.
 *  @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] = Option(wr.underlying.get)
}

/**
 *  @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]