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principles:open-closed_principle [2013-03-18 09:44] – external edit 127.0.0.1principles:open-closed_principle [2022-03-02 23:55] (current) – [Principle Statement] tory
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-====== Open-Closed Principle ======+====== Open-Closed Principle (OCP) ======
  
 ===== Variants and Alternative Names ===== ===== Variants and Alternative Names =====
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 ===== Context ===== ===== Context =====
 /* fill in contexts here: */ /* fill in contexts here: */
-  * [[contexts:Object-Oriented Design]] +  * [[contexts:Object-Oriented Design]] 
 +  * [[contexts:API Design]] 
  
  
 ===== Principle Statement ===== ===== Principle Statement =====
  
-Modules should be open for enhancement but closed for modification.+Modules should be open for extension but closed for modification.
  
  
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 ===== Caveats ===== ===== Caveats =====
  
-See section [[#contrary principles]].+Beware that wrong application of OCP may lead to the anti-pattern [[anti-patterns:onion]]. 
 + 
 +See also section [[#contrary principles]].
  
  
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 ===== Examples ===== ===== Examples =====
  
 +===Client Repository=== 
 +Let's say the high-level module (your business logic), wants to be able to add or remove clients to the database. Instead of it talking to the database directly, it defines an interface called ClientRepository which contains the methods the business logic needs ([[dependency_inversion_principle|DIP]]). Now you go along and implement a MySQLClientRepository. Some time in the future, you are asked to switch to an oracle database. You can now, without modifying any code from your business logic, switch to the oracle database: by extending ClientRepository to implement OracleClientRepository. You just need to wire an OracleClientRepository instance to the business logic and you have made the switch without modifying any business logic code.
 ===== Description Status ===== ===== Description Status =====
 /* Choose one of the following and comment out the rest: */ /* Choose one of the following and comment out the rest: */
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   * Robert C. Martin: //Agile Software Development, Principles, Patterns, and Practices//, p. 99pp.   * Robert C. Martin: //Agile Software Development, Principles, Patterns, and Practices//, p. 99pp.
   * [[http://www.butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod|ButUncleBob: Principles of OOD]]   * [[http://www.butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod|ButUncleBob: Principles of OOD]]
 +
 +===== Discussion =====
 +
 +Discuss this wiki article and the principle on the corresponding [[talk:principles:Open-Closed Principle|talk page]].
  
principles/open-closed_principle.1363596280.txt.gz · Last modified: 2013-05-19 22:10 (external edit)