Dealing With Duplicated Code

Slides for my presentation at Bulgaria Web Summit 2015 about Code Duplication, what it is, problems, how to find and how to deal with it.

Transcript

1. DealingWith
   DuplicatedCode
   Duplicated
   Duplicated
   BulgariaWebSummit
   April 2014
   Duplicated
   

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2. Evaldo Junior
   @InFog9
   evaldojunior.com
   #brazil #germany
   #php #linux #opensource
   

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3. BambergGermany
   We'reHiring!
   

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4. DéjàVu
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5. Wikipedia
   Duplicate code is a computer
   programming term for a sequence
   of source code that occurs more
   than once, either within a program
   or across different programs
   owned or maintained by the same
   entity.
   

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6. CodeSmells
   #1
   

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7. DRY
   Don't Repeat Yourself
   

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8. WET
   We Enjoy Typing
   Write Everything Twice
   

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9. Duplication is not only
   “DuplicatedCode”
   

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10. Why
    do we duplicate?
    

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11. Why?
    Copy/Paste is easy
    ctrl+c / ctrl+v
    

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12. Why?
    In a hurry to deliver
    You know, it's for yesterday!
    

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13. Why?
    Lack of codebase
    knowledge
    - Hm, I didn't know our codebase had this already.
    

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14. Duplication's
    Problems
    

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15. Problems
    Increase codebase's
    size
    Five thousand lines' controllers.
    

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16. Problems
    Fix the same bug more
    than once
    - Ok, now it works in that page, but not in this one.
    

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17. Problems
    Adding not standard
    new features
    - Why are the dates not formated using my preference?
    

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18. Is duplication always a
    bad thing?
    

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19. Example of duplication
    

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20. View Slide

21. Hey! We need to
    support USA users!
    

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22. View Slide

23. Support user defined
    date format
    

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24. View Slide

25. One possible solution
    

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26. View Slide

27. Should I actively
    search for
    duplications?
    

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28. PHPCPD
    

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29. PHPCPD
    

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30. I found some
    duplications!
    What should I do now?
    

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31. Apply Some
    Patterns
    

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32. Different methods
    

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33. Different methods
    

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34. Extract Method
    

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35. Extract Method
    

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36. Different classes
    

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37. Extract Class
    

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38. Different projects
    

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39. Extract Package
    

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40. Same attribute in
    different classes
    

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41. Pull Up Field
    

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42. Thank you!
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