scala.Proxy

trait Proxy extends Any

This class implements a simple proxy that forwards all calls to the public, non-final methods defined in class Any to another object self. Those methods are:

def hashCode(): Int
def equals(other: Any): Boolean
def toString(): String

Note: forwarding methods in this way will most likely create an asymmetric equals method, which is not generally recommended.

Concrete 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)

Full Source:

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://www.scala-lang.org/           **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala

/** This class implements a simple proxy that forwards all calls to
 *  the public, non-final methods defined in class `Any` to another
 *  object self.  Those methods are:
 *  {{{
 *    def hashCode(): Int
 *    def equals(other: Any): Boolean
 *    def toString(): String
 *  }}}
 *  '''Note:''' forwarding methods in this way will most likely create
 *  an asymmetric equals method, which is not generally recommended.
 *
 *  @author  Matthias Zenger
 *  @version 1.0, 26/04/2004
 */
trait Proxy extends Any {
  def self: Any

  override def hashCode: Int = self.hashCode
  override def equals(that: Any): Boolean = that match {
    case null  => false
    case _     =>
      val x = that.asInstanceOf[AnyRef]
      (x eq this.asInstanceOf[AnyRef]) || (x eq self.asInstanceOf[AnyRef]) || (x equals self)
  }
  override def toString = "" + self
}

object Proxy {
  /** A proxy which exposes the type it is proxying for via a type parameter.
   */
  trait Typed[T] extends Any with Proxy {
    def self: T
  }
}