Mixin: Difference between revisions
added Dylan |
m small style change |
||
| Line 1: | Line 1: | ||
In [[object-oriented programming language]]s, a '''mixin''' is an approach to implementing [[class (computer science)|class]]es that differs from the most widely-used approach, |
In [[object-oriented programming language]]s, a '''mixin''' is an approach to implementing [[class (computer science)|class]]es that differs from the most widely-used approach, which originated from the programming language [[Simula]]. Mixins were first used in [[Flavors]], which was an approach to object-orientation used in [[Lisp Machine Lisp]]. The advantage of mixins is that they encourage [[code reuse]] and avoid well-known pathologies associated with [[multiple inheritance]], but mixins introduce their own set of compromises. |
||
==Definition and implementation== |
==Definition and implementation== |
||
Revision as of 16:10, 17 April 2006
In object-oriented programming languages, a mixin is an approach to implementing classes that differs from the most widely-used approach, which originated from the programming language Simula. Mixins were first used in Flavors, which was an approach to object-orientation used in Lisp Machine Lisp. The advantage of mixins is that they encourage code reuse and avoid well-known pathologies associated with multiple inheritance, but mixins introduce their own set of compromises.
Definition and implementation
In Simula, classes are defined in a block in which attributes, methods and class initialization are all defined together, and so all the methods that can be invoked on a class are defined together, and the definition of the class is complete.
With mixins the class definition defines only the attributes and parameters associated with that class; methods are left to be defined elsewhere, as in Flavors and CLOS, and are called "generic functions". These generic functions are functions which are defined in multiple cases by type dispatch.
Other than Flavors and CLOS, some languages that use mixins are:
- D programming language
- Dylan programming language
- Python programming language
- Ruby programming language
- Scala programming language
- XOTcl (an object system for Tcl)
Commentary
Some of the functionality of mixins is provided by interfaces in popular languages like Java and C#, but since an interface only specifies what the class must support and cannot provide an implementation, they are only useful for providing polymorphism. Another class, providing an implementation and dependent with the interface, is useful for refactoring common behavior into a single place.
See also
External links
- Wiki entry at Cunningham & Cunningham, Inc.
- Mixins in ActionScript.
- Scala Overview: Mixin Class Composition - a step-by-step example in Scala
- The Common Lisp Object System: An Overview by Richard P. Gabriel and Linda DeMichiel provides a good introduction to the motivation for defining classes by means of generic functions.
 | This computing article is a stub. You can help Wikipedia by expanding it. |