Editing Delegation pattern (section)

{{Short description|Design pattern in object-oriented programming}}
In [[software engineering]], the '''delegation pattern''' is an [[object-oriented programming|object-oriented]] [[design pattern]] that allows [[object composition]] to achieve the same [[code reuse]] as [[inheritance (object-oriented programming)|inheritance]].

In delegation, an [[object (computer science)|object]] handles a request by delegating to a second object (the ''delegate'').  The delegate is a [[helper object]], but ''with the original context''. With language-level support for delegation, this is done implicitly by having <code>[[self (computer science)|self]]</code> in the delegate refer to the original (sending) object, not the delegate (receiving object). In the delegate pattern, this is instead accomplished by explicitly passing the original object to the delegate, as an argument to a method.<ref>Gamma et al. 1994</ref> "Delegation" is often used loosely to refer to the distinct concept of [[forwarding (object-oriented programming)|forwarding]], where the sending object simply uses the corresponding member on the receiving object, evaluated in the context of the ''receiving'' object, not the original object.

This article uses "sending object/receiving object" for the two objects, rather than "receiving object/delegate", emphasizing which objects send and receive the delegation call, not the original call.