The Power Of Refactoring (PHPCon Italia)


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The slides of my Power of Refactoring talk as I did it at the PHPCon Italia in Rome

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The Power Of Refactoring (PHPCon Italia)

  1. 1. The Power of Refactoring Stefan Koopmanschap PHPCon Italia, Rome, March 19 2009
  2. 2. What will we do? What is refactoring? Why refactoring? When refactoring? Requirements HOWTO 2
  3. 3. Stefan Koopmanschap Who is he? 3
  4. 4. About me Professional Services Consultant at Ibuildings 10 years of PHP experience auto didact married, 2 kids, 6 cats, a bunch of fish Apple lover music addict symfony advocate 4
  5. 5. Refactoring What is it? 5
  6. 6. Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior. Its heart is a series of small behavior preserving transformations. Each transformation (called a 'refactoring') does little, but a sequence of transformations can produce a significant restructuring. Since each refactoring is small, it's less likely to go wrong. The system is also kept fully working after each small refactoring, reducing the chances that a system can get seriously broken during the restructuring. (Martin Fowler - 6
  7. 7. Code refactoring is the process of changing a computer program's code to make it amenable to change, improve its readability, or simplify its structure, while preserving its existing functionality. (Wikipedia) 7
  8. 8. What Code refactoring is the process of changing a computer program's internal structure without modifying its external behavior or existing functionality. 8
  9. 9. Why This is usually done to improve code readability, simplify code structure, change code to adhere to a given programming paradigm, improve maintainability, or improve extensibility. 9
  10. 10. Improve readability 10
  11. 11. Improve maintainability 11
  12. 12. Extend/change/implement 12
  13. 13. Is it the holy grail? 13
  14. 14. Rewrite A rewrite in computer programming is the act or result of re-implementing a large portion of existing functionality without re-use of its source code. When the rewrite is not using existing code at all, it is common to speak of a rewrite from scratch. When instead only parts are re- engineered, which have otherwise become complicated to handle or extend, then it is more precise to speak of code refactoring. (Wikipedia) 14
  15. 15. Refactor vs Rewrite 15
  16. 16. Refactor vs Rewrite Refactor whenever it is possible 15
  17. 17. Refactor vs Rewrite Refactor whenever it is possible Big change? Try to cut it into smaller units 15
  18. 18. Refactor vs Rewrite Refactor whenever it is possible Big change? Try to cut it into smaller units Still have to break the API? Go ahead, and rewrite! 15
  19. 19. Refactor vs Rewrite Refactor whenever it is possible Big change? Try to cut it into smaller units Still have to break the API? Go ahead, and rewrite! Don’t take the decision in 5 minutes 15
  20. 20. Refactor vs Rewrite Refactoring takes less effort Nice for you Better for the quality of your work Breaking the API is more work Ensure all calling code is altered as well Update your unit tests Update your documentation 16
  21. 21. Requirements for successful refactoring 17
  22. 22. Requirements Codebase knowledge Structured API Unit testing 18
  23. 23. Codebase knowledge Know what to change quickly Be aware of your changes Be aware of impact of your changes on other components 19
  24. 24. Structured API Refactoring DOES NOT REPLACE design! You need a good API that allows internal changes Additions to existing API’s should not change existing API Keep small “units” 20
  25. 25. Unit testing 21
  26. 26. Unit testing Unit testing is your first point of QA They safeguard you from unexpected side effects Test - Change - Test 22
  27. 27. When? Timing of refactoring 23
  28. 28. Two moments of refactoring Big chunks Continuous refactoring 24
  29. 29. Big Chunks As you encounter problems, you keep track • Ticketing system • TODO list • Inline comments Schedule one or more moments in your project • Work through your list • Refactor them 25
  30. 30. Big Chunks work? Advantages • Set times for refactoring • Focus on your project when you need to • Works well for functional changes Disadvantages • Refactoring gets cancelled first with tight deadlines • You may have forgotten specific solutions already 26
  31. 31. Continuous Refactoring Refactor while you work Encounter a problem, fix it! 27
  32. 32. Continuous Refactoring works? Advantages • No need to schedule seperate time • Continuous improvement of your code Disadvantages • Danger of losing the balance between tasks and refactoring 28
  33. 33. Who should refactor? 29
  34. 34. Who should refactor? Someone with knowledge of the codebase • Or at least the part that is being refactored Not necessarily the code owner 30
  35. 35. An example user authentication 31
  36. 36. A test-driven approach 32
  37. 37. My first implementation 33
  38. 38. My first implementation 33
  39. 39. A more dynamic version 34
  40. 40. A more dynamic version 34
  41. 41. Tips and tricks 35
  42. 42. Some tips and tricks Write unit tests before you start refactoring Code documentation (phpDoc) is your friend Don’t trust your IDE’s refactoring options 36
  43. 43. Looking back What is refactoring? Why do we want to refactor? Is it the holy grail? Refactoring vs Rewriting Requirements How to do it Tips and tricks 37
  44. 44. The Power of Refactoring 38
  45. 45. Creative Commons Rocks! Readability: 471634239/ (by-nc-sa/2.0) Maintainability: 2117680144/ (by-nc-sa/2.0) Extend: 221951988/ (by-nc-sa/2.0) Holy Grail: 153921142/ (by/2.0) Würst test ever: 1341229619/ (by-nc-nd/2.0) 39
  46. 46. Questions ? 40
  47. 47. Thank you! Contact details: Stefan Koopmanschap