Rule of three (computer 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[1] 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.
See also
References
- ^ Refactoring: Improving the Design of Existing Code by Martin Fowler (ISBN: 978-0201485677)