1. REFACTORING
THE GOOD, THE BAD AND THE UGLY
Jeroen Thora | @jeroenthora acrobat

2. JEROEN THORA
▸ Backend developer @ Kunstmaan | Accenture interactive
▸ Opensource contributor and maintainer
▸ Knplabs/php-github-api, Bernard, Bootstrap-
datepicker, ...

3. WHAT WE WILL TALK ABOUT
▸ Introduction to legacy code
▸ Steps to refactor
▸ Code smells (and solutions)
▸ Tools & resources
▸ Summary

4. LEGACY CODE

5. HOW YOU FEEL

6. TECHNICAL DEBT
▸ bit by bit the code is corrupted
▸ Accumulation of technical debts
▸ Any healthy project will collect some technical debt
▸ Forced to pay the debt
▸ Paying this debt is called refactoring

7. REFACTORING
"It's a process of restructuring existing
code, altering it's internal structure without
changing it's external behaviour"

8. BENEFITS - CODE
▸ Will look clean
▸ Easy to understand
▸ Easy to change / maintain

9. BENEFITS - YOU
▸ Will code faster
▸ Spot bugs easier
▸ More confident to develop the code

10. CONVINCING YOUR CLIENT/BOSS
▸ Explain what technical debt means
▸ Use actual examples like cost to on-board team
members, development of features, ...
▸ Integrate cost in the offer
▸ Refactor with clear short-term goals in mind
▸ Point out that you want the best for your customer
ONCE OWNER CONVINCED
FREEDOM TO MOVE THE PROJECT IN THE RIGHT
DIRECTION.

11. WARNINGS (DON'TS)
▸ The big red button switch (Green field approach)
▸ Migration of data
▸ Mistakes old and new
▸ Keeping up with the business
GENERAL ADVICE
DON'T START OVER. IMPROVE WHAT YOU HAVE!

12. HOW TO START
▸ Make problems visible
▸ Monitor your environment
▸ Visualise errors
▸ Sentry / grafana dashboard / ...

13. *insert screenshot sentry + grafana dashboard*

14. TEAM
▸ The boyscout rule - Robert C. Martin (Uncle Bob)
▸ "Leaving the camping ground cleaner than you found it"
▸ You have to care
▸ The whole team has to care
▸ Discipline
▸ Keep taking small steps
▸ Small victories generate momentum

15. BALL OF MUD
▸ Isolate the messy part
▸ Push dependencies out from the outside to the core
▸ Controllers -> services -> libraries -> ...
▸ Making code self-contained
▸ Thus making it testable

16. BALL OF MUD
▸ Small iterations
▸ Easy to detect regressions
▸ Almost risk free refactoring
▸ Together with tests

18. BUILD CONFIDENCE
▸ High level tests of business critical logic
▸ Checkout flow, member registration, ....
▸ Unit tests of small components
▸ Clear input and a clear output.
▸ Make sure that bit of code keeps behaving as expected.
GENERAL ADVICE
DON'T (TRY TO) TEST EVERYTHING.

19. YOU (OR MY REFLECTIONS)
▸ Becoming a better developer
▸ Learning to recognise bad code
▸ Back to basics
▸ People are generating shiny new legacy constantly
▸ Fun and rewarding

20. CODE SMELLS
▸ Bloaters
▸ Unneeded stuff
▸ Change preventers
▸ Complex if statements
▸ Bad naming
IF IT STINKS, CHANGE IT!
An indication of a deeper problem in the system

21. BLOATERS
Long method Long parameter list Large class
Image source: refactoring.guru

22. BLOATERS
Long method Long parameter list Large class
▸ Move logic to
private methods
▸ Group common
logic
▸ Keep class
hierarchy small
▸ Avoid classes with
same behaviour
▸ Enforce single
responsibility
principle
▸ Group in object
▸ Remove method
call result params

23. UNNEEDED STUFF
Dead code Useless comments
Future code
not in use
Image source: refactoring.guru

24. CHANGE PREVENTERS
Shotgun Surgery
Image source: refactoring.guru

25. CHANGE PREVENTERS
▸ Avoid classes with same behaviour
▸ Move duplicated code
▸ Don't over engineer
Shotgun Surgery

26. COMPLEX IF-STATEMENTS

27. BAD NAMING

28. RESOURCES / TOOLS
▸ Phpmd
▸ Phpcpd
▸ Scrutinizer
▸ Php-cs-fixer
▸ Php Inspections EA (ultimate)

29. RESOURCES / TOOLS
https://refactoring.guru

30. SUMMARY
▸ Live by the boyscout rule
▸ Get your boss/client in the refactoring mindset
▸ Small steps at a time
▸ Monitor your application
▸ To improve yourself, improve your code

31. THANKS!
QUESTIONS?
@jeroenthora acrobat