Rule of three (programming)
- Rule of three (programming)
Rule of three is a code Refactoring rule of thumb to decide when a replicated piece of code should be replaced by a new procedure. It states that you are allowed to copy and paste the code once, but that when the same code is replicated three times, it should be extracted into a new procedure. The rule was introduced by Martin Fowler in Refactoring [Refactoring: Improving the Design of Existing Code by Martin Fowler (ISBN: 978-0201485677)] and attributed to Don Roberts.
Duplication in programming is a bad practice because it makes the code harder to maintain. When the rule encoded in a replicated piece of code changes, whoever maintains the code will have to change it in all places correctly. This process is error-prone and often leads to problems. If the code exists in only one place, then it can be easily changed there.
ee also
* Don't repeat yourself (DRY)
* Refactoring
References
External links
* [http://c2.com/cgi/wiki?DontRepeatYourself DRY (c2.com)]
* [http://c2.com/cgi/wiki?OnceAndOnlyOnce Once and Only Once (c2.com)]
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