Principles Wiki

User Tools

Site Tools

You are here: Principles Wiki » Principles » Don't Repeat Yourself (DRY)
principles:don_t_repeat_yourself

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
Next revisionBoth sides next revision
principles:don_t_repeat_yourself [2021-09-02 11:46] – old revision restored (2021-05-19 10:22) 65.21.179.175principles:don_t_repeat_yourself [2021-09-02 11:47] – old revision restored (2021-05-19 10:22) 65.21.179.175
Line 10: Line 10:
   * [[contexts:Object-Oriented Design]]   * [[contexts:Object-Oriented Design]]
  
-===== Definition =====+===== Principle Statement =====
  
 > "Every piece of knowledge must have a single, unambiguous, authoritative representation within a system."((Andrew Hunt and David Thomas: //The Pragmatic Programmer: From Journeyman to Master//; see [[http://pragprog.com/the-pragmatic-programmer/extracts/tips|List of Tips]].)) > "Every piece of knowledge must have a single, unambiguous, authoritative representation within a system."((Andrew Hunt and David Thomas: //The Pragmatic Programmer: From Journeyman to Master//; see [[http://pragprog.com/the-pragmatic-programmer/extracts/tips|List of Tips]].))
Line 23: Line 23:
  
 If there are several representations of the same information (be it code or any other form of information), all of them have to be maintained separately while changing at the same time. There is the danger that at some point in time the different representations diverge which is a fault. But if there is a single source of truth, there is only one place where changes have to be applied. Then the representations cannot diverge. If there are several representations of the same information (be it code or any other form of information), all of them have to be maintained separately while changing at the same time. There is the danger that at some point in time the different representations diverge which is a fault. But if there is a single source of truth, there is only one place where changes have to be applied. Then the representations cannot diverge.
 +
 +
 +===== Strategies =====
  
  
Line 45: Line 48:
 ==== Specializations ==== ==== Specializations ====
  
-  * [[principles:Generalization Principle]] A generalized solution avoids duplication.+  * [[principles:Generalization Principle]]: A generalized solution avoids duplication.
   * [[principles:Once And Only Once]]: This is the aspect of DRY which is concerned with the avoidance of (code) duplication.   * [[principles:Once And Only Once]]: This is the aspect of DRY which is concerned with the avoidance of (code) duplication.
 +  * [[principles:Single Choice Principle]]: Duplication can also be duplication of information about a set of possibilities. The SCP is about this aspect.
 +  * [[principles:Write Code That Writes Code]]: This is the code generation aspect of DRY.
  
 ==== Contrary Principles ==== ==== Contrary Principles ====
Line 57: Line 62:
 ==== Principle Collections ==== ==== Principle Collections ====
  
 +{{page>collections:OOD Principle Language#Box}}
  
 ===== Example ===== ===== Example =====
Line 73: Line 79:
   * [[wp>Don't repeat yourself]]   * [[wp>Don't repeat yourself]]
   * [[http://programmer.97things.oreilly.com/wiki/index.php/Don't_Repeat_Yourself|97things: Don't_Repeat_Yourself]]   * [[http://programmer.97things.oreilly.com/wiki/index.php/Don't_Repeat_Yourself|97things: Don't_Repeat_Yourself]]
 +
principles/don_t_repeat_yourself.txt · Last modified: 2021-10-18 21:27 by christian