as used at the International PHP Conference 2008 in Mainz on October 30th 2008

1. The Power of
Refactoring
Why doing things three times may speed up
development
The Power of
Refactoring

2. What will we do?
• Intro
• What is refactoring?
• Why refactoring?
• It saves time?
• Some examples
The Power of
Refactoring

3. Introduction
• Professional Services Consultant at
Ibuildings
• Secretary of Dutch PHP Usergroup
• symfony advocate
• husband and father (2 times)
• 7 cats and a bunch of fish
The Power of
Refactoring

4. Refactoring
The Power of
Refactoring

5. 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 - Refactoring.com)
The Power of
Refactoring

6. 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)
The Power of
Refactoring

7. So basically...
• Improve small parts of the code for...
• Readability
• Performance improvement
• Implementation or change of logic
The Power of
Refactoring

8. But watch out!
• It should not break existing functionality
• Remain a consistent API/interface
The Power of
Refactoring

9. Refactoring v Rewriting
• Refactoring
• Consistent API
• Internal logic changes
• No need to alter unit tests or API docs
The Power of
Refactoring

10. Refactoring v Rewriting
• Rewriting
• Refactoring won’t help you anymore
• More complex: alter unit tests, alter
calling code, alter documentation
The Power of
Refactoring

11. Why refactoring?
• Prototyping
• Unclear specs
• Project overview
• Improve bad code
The Power of
Refactoring

12. Why refactoring?
• Prototyping
• Quickly have a clickable interface
• No need for full functionality yet
• As long as structure is OK, refactoring
into final product is easy
The Power of
Refactoring

13. Why refactoring?
• Unclear specs
• Something needs to be implemented
• but you don’t know how!
• Create a basic API and call it
• Implement it later
The Power of
Refactoring

14. Why refactoring?
• Project overview
• Similar to unclear specs
• Create your project API skeleton with
dummy responses
• Bit by bit, work on actually adding
functionality
The Power of
Refactoring

15. Why refactoring?
• Improve bad code (PHP4 code, anyone?)
• Security
• Performance
• Best Practices
The Power of
Refactoring

16. by-nc/2.0 - gilest - http://www.flickr.com/photos/gilest/
The Power of
Refactoring

17. by-nc-sa/2.0 - evymoon - http://www.flickr.com/photos/evymoon_quatrain_quotidien/
The Power of
Refactoring

18. Does it save time?
• Yes! Yes it does!
• Readability of your code
• Maintainability of your code
• Higher quality of your code
• Unit testing to ensure stability
The Power of
Refactoring

19. Does it save time?
• Prototyping
• Don’t start from scratch, use your proto
• Only rewrite those things that really
need it
The Power of
Refactoring

20. Does it save time?
• Unclear specs
• Don’t write things fully until you need to
• Think of a good API saves changing all
calls
The Power of
Refactoring

21. Does it save time?
• Project overview
• Know the big picture
• Keep focus on the small part you work
on
The Power of
Refactoring

22. Does it save time?
• Improve bad code
• Better readability means faster coding
• More stable code reduces bug fixing
The Power of
Refactoring

23. Some requirements
• Unit/functional tests need to be in place
• API needs to remain exactly the same
• API needs to be good enough
• if not, then rewrite instead of refactor
The Power of
Refactoring

24. Some examples
The Power of
Refactoring

25. Project A: Unclear
specs
• authentication system is still unknown
• project or iteration deadline is nearing
• let’s first simulate the authentication
The Power of
Refactoring

26. Project A: Unclear
specs
• Same could also apply for writing a
prototype
• Not all details are known
• Short deadline
• Doesn’t need to fully work yet
The Power of
Refactoring

27. Project A: Unclear
specs
The Power of
Refactoring

28. Project A: Unclear
specs
The Power of
Refactoring

29. Project A: Unclear
specs
• Halfway the project, client finally decides
• Easy to implement: just refactor the
authenticate method
• Rest of the code does not care, as long as
you keep the API the same
The Power of
Refactoring

30. Project A: Unclear
specs
The Power of
Refactoring

31. Nothing changes
• This still works!
The Power of
Refactoring

32. Documentation helps
• Good rule of thumb
• If you need to change
the method
documentation,
reconsider
The Power of
Refactoring

33. Project B: Code
improvement
• You took over management of another
developer’s code
• You wrote some crappy code yourself
• Advancements in technology made better
things possible (much more likely! ;-)
The Power of
Refactoring

34. Project B: Code
improvement
The Power of
Refactoring

35. Project B: Code
improvement
The Power of
Refactoring

36. Nothing changes
• This still works!
The Power of
Refactoring

37. Ensuring your API
• Documentation
• Changing your @param values?
• Changing your @return value?
• Adding/changing/removing @throws?
The Power of
Refactoring

38. Ensuring your API
• Unit Tests
• PHPUnit/SimpleTest/lime
• Test for all situations (also exceptions)
• Test for the unexpected!
The Power of
Refactoring

39. Ensuring your API
• Continuous Integration
• CruiseControl/phpUnderControl/Xinc
• Continuously test your code
• Alert through e-mail, SMS, Nabaztag
The Power of
Refactoring

40. Further reading
• http://www.refactoring.com/
• http://phpimpact.wordpress.com/
2008/09/14/code-refactoring-guidelines/
• http://chrissterling.gettingagile.com/
2008/10/13/refactoring-how-far-should-i-go/
The Power of
Refactoring

41. Commercial break
• http://www.leftontheweb.com/ - my
personal blog
• http://www.symfony-framework.nl/ - my
dutch symfony advocacy site
• http://www.ibuildings.com/ - my employer
(we’re hiring! contact me!)
The Power of
Refactoring

42. Questions?
The Power of
Refactoring