Editing Class (computer programming) (section)

===Metaclass===
{{Main|Metaclass}}

A metaclass is a class where instances are classes.{{sfn|Booch|1994|p=133-134}} A metaclass describes a common structure of a collection of classes and can implement a [[design pattern (computer science)|design pattern]] or describe particular kinds of classes. Metaclasses are often used to describe [[software framework|framework]]s.<ref>{{Cite web|url=http://pharo.gforge.inria.fr/PBE1/PBE1ch14.html|title=13 Classes and metaclasses|website=pharo.gforge.inria.fr|access-date=2016-10-31|archive-date=2021-02-24|archive-url=https://web.archive.org/web/20210224193450/http://pharo.gforge.inria.fr/PBE1/PBE1ch14.html|url-status=dead}}</ref>

In some languages, such as [[Python (programming language)|Python]], [[Ruby (programming language)|Ruby]] or [[Smalltalk]], a class is also an object; thus each class is an instance of a unique metaclass that is built into the language.<ref name="pythondata model"/><ref>{{cite web |url=https://docs.ruby-lang.org/en/master/Class.html |title=class Class}}</ref>
{{sfn|Booch|1994|p=134}}
The [[Common Lisp Object System]] (CLOS) provides [[Metaobject|metaobject protocols]] (MOPs) to implement those classes and metaclasses.<ref>{{cite web |url=http://www.alu.org/mop/concepts.html#introduction |title=MOP: Concepts |work=The Common Lisp Object System MetaObject Protocol |publisher=Association of Lisp Users |access-date=2012-05-08 |archive-url=https://web.archive.org/web/20101115095930/http://www.alu.org/mop/concepts.html#introduction |archive-date=2010-11-15 |url-status=dead}}</ref>