CSC/ECE 517 Fall 2009/wiki3 1 co

Software Design Anti-Patterns

  Not all patterns are good. Anti-patterns are patterns that initially seem effective, but over time you learn that they lead you into traps. 
      - Scott Klement, Anti-Patterns: Avoid the Programming Dark Side

In this article, we will describe several software design patterns which have been categorized as "anti patterns": Programming approaches which are not uncommon and which can lead to poor program design and performance.

What are Anti-Patterns?

Different texts define the term anti-patterns in different ways:

• "An AntiPatern is a literary form that describes a commonly occurring solution to a problem that generates decidedly negative consequences." - AntiPatterns: Refactoring Software, Architectures, and Projects in Crisis
• "Anti-patterns are patterns that initially seem effective, but over time you learn that they lead you into traps." - Anti-Patterns: Avoid the Programming Dark Side
• Over the last decade we have witnessed the maturity of both best practices...and worst practices (as manifested in the anti-patterns movement...). - Patterns of Anti-Patterns?, Journal of Object Technology

In each definition, the implementer of the anti-pattern is trying to solve a problem in a common way, however the common way is a bad design that can lead to unintended consequences. Some of the reasons cited in the AntiPatterns book as to why these anti-patterns have been used include: Haste, sloth (or laziness), ignorance, apathy, and pride. Studying anti-patterns can at least help assist the potential anti-pattern implementer in the ignorance category.

Considerations When Writing Anti-Patterns

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Anti-Pattern Examples

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The Blob or God Class

Anti-Pattern Problem

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Refactored Solution

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Example

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Lava Flow

Anti-Pattern Problem

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Refactored Solution

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Example

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Poltergeists

Anti-Pattern Problem

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Refactored Solution

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Example

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Golden Hammer

Anti-Pattern Problem

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Refactored Solution

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Example

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Spaghetti Code

Anti-Pattern Problem

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Refactored Solution

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Example

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Cut-and-Paste Programming

Anti-Pattern Problem

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Refactored Solution

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Example

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Conclusion

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References

• www.antipatterns.com
• W. J. Brown et al., AntiPatterns: Refactoring Software, Architectures, and Projects in Crisis, John Wiley & Sons, Inc., New York, NY, 1998.
• S. Klement, Anti-Patterns: Avoid the Programming Dark Side, 2008
• Wikipedia entry: Anti-pattern
• Anti Patterns Catalog offered by Cunningham & Cunningham, Inc.
• What is an AntiPattern? from Sourcemaking.com
• Anti-Patterns and Worst Practices – You’re Doing it Wrong!
• M. H. Dodani,Patterns of Anti-Patterns?, Journal of Object Technology, Vol 5, No 6, pp 29-33, 2006
• E. Gamma et al,Design Patterns: Elements of Reusable Object-Oriented Software, Addison-Wesley Professional, 1994.