Working With Legacy Rails Apps

Transcript

1. Working With Legacy
   Rails Apps
   @this_ahmed
   

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2. Working With Legacy
   Rails Apps
   @this_ahmed
   

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3. legacy code
   • untested code (Michael C. Feathers)
   • code someone else wrote (old gems, outsourcing,
   maintainers left)
   • difficult to work with
   • risky to change
   • but serves a useful function
   

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4. googling legacy code …
   

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5. every project has
   legacy code?
   

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7. • learning & experimenting
   • ambitious applications
   • big project, developer churn, hiring outside help
   • bad code … even with the best of intentions
   • “Technical debt”
   

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9. –Robert C. Martin
   “Even the most disciplined development team,
   knowing the best principles, using the best
   patterns, and following the best practices will
   create messes from time to time.”
   

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10. in the face of legacy
    code you can …
    

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12. or…
    

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14. Useful techniques
    

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15. Rebuild Refactor
    

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16. –Robert C. Martin
    “…taking a tangled, opaque, convoluted
    system and slowly, gradually, piece by piece,
    step by step, turning it into a simple, nicely
    structured, well-designed system.”
    

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17. Boy Scout Rule
    Clean up around you work area. Small fixes; small
    refractors.
    

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18. cover and modify
    • add unit test
    • test passes
    • modify code
    • test passes
    

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19. use mock objects to
    break dependencies
    

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21. mock dependencies
    

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22. break complicated
    dependencies with
    seams
    

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24. seam => put in method + stub
    

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25. first step to later
    refactor
    

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26. i don’t understand this
    code…
    

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27. Ask someone
    

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28. code archeology
    

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29. code archeology
    git blame / Github
    

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30. code archeology
    search code
    for context
    git blame / Github
    

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31. code archeology
    project management
    ticket
    git blame / Github
    search code
    for context
    

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32. code archeology
    git blame / Github project management
    ticket
    commit message
    search code
    for context
    

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33. review
    • boy scout rule
    • cover and modify
    • break dependencies with mocks and seams
    • understand code with archeology
    

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34. some parting thoughts
    

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35. unit test
    

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38. • code review
    • small git branches
    • add lots of context in pull request / commit
    message
    

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