A brief introduction to the agile practice of Refactoring

1. Refactoring
An Introduction
Giorgio Vespucci

2. “Software must be soft: it
has to be easy to change
because it will change
despite our misguided
efforts otherwise.”
The Pragmatic Programmers

3. What we want
Robustness
Simplicity
Softness

4. What we see
Fragility
Complexity
Rigidity

5. Unreadable
code is…

6. Hard to modify

7. Duplicated
code is…

8. Hard to modify

9. Complex
code is…

10. Hard to modify

11. Refactored
code is...

12. Easier to
understand

13. Cheaper
to modify

14. Clean
code

15. Better
code

16. Refactored
code shows...

17. Changes to its
internal structure

18. But no change to
observable behavior

19. “So what?”

20. Try to understand
this Java code

21. java.util.Calendar c =
java.util.Calendar.getInstance();
c.set(2005, java.util.Calendar.NOVEMBER, 20);
c.getTime();

22. Uhm... a Date...

23. And now this code

24. october(23,2008);

25. Hey, mum! It's a Date!

26. “Any fool
can write code
that a computer
can understand.”

27. “Good programmers write
code
that humans
can understand.”
Martin Fowler - Refactoring

28. What do we
need ?

29. “If you want to refactor, the essential
precondition is having solid tests.”
Martin Fowler - Refactoring

30. Measures matter

31. Where to start ?

32. Look at
the code

33. Sniff
the code

34. Does it smell ?

35. Duupliccateed code?
Loooooong method?
L a r g e class?

36. The Refactoring cycle
1) Choose the worst smell
2) Select a refactoring
3) Apply the refactoring
4) Run all the tests

37. little steps

38. Great
results

39. Must-have books on Refactoring
Refactoring: Improving the Design of Existing
Code
(Addison-Wesley Object Technology Series)
Martin Fowler
Refactoring Workbook
(Addison-Wesley Object Technology Series)
William C. Wake
Refactoring to Patterns
(Addison-Wesley Signature Series)
Joshua Kerievsky

40. Online resources
Smells to refactor
http://wiki.java.net/bin/view/People/SmellsToRefactorings
Alpha list of refactoring
http://www.refactoring.com/catalog/index.html
Refactoring Workbook Website
http://xp123.com/rwb/
Refactoring to Patterns catalog
http://industriallogic.com/xp/refactoring/catalog.html