Composition over inheritance: Difference between revisions

Revision as of 17:29, 18 August 2022

Revision as of 05:52, 30 August 2022

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{{Short description|Software design pattern}}

{{Cleanup bare URLs|date=August 2022}}

{{Confusing|date=October 2015}}

[[File:UML diagram of composition over inheritance.svg|thumb|right|444px|This diagram shows how the fly and sound behavior of an animal can be designed in a flexible way by using the composition over inheritance design principle.<ref name="FHDPs" />]]

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An implementation of composition over inheritance typically begins with the creation of various [[Interface (computing)#In object-oriented languages|interfaces]] representing the behaviors that the system must exhibit. Interfaces can facilitate [[Polymorphism (computer science)|polymorphic]] behavior. Classes implementing the identified interfaces are built and added to [[business ___domain]] classes as needed. Thus, system behaviors are realized without inheritance.

In fact, business ___domain classes may all be base classes without any inheritance at all. Alternative implementation of system behaviors is accomplished by providing another class that implements the desired behavior interface. A class that contains a reference to an interface can support implementations of the interface—a choice that can be delayed until [[Runtime_Runtime (program_lifecycle_phaseprogram lifecycle phase)|runtime]].

==Example==