Writing code is easy but writing maintainable code is almost impossible. During this talk I will discuss some of the principles of coding that relates to WordPress but goes beyond that.

1. WRITING CLEAN AND MAINTAINABLE CODE
WordCamp Norway 2015

2. Marko Heijnen
• Lead developer of GlotPress
• Core contributor for WordPress
• Working for 1&1 as their
WordPress specialist
• Fan of new technologies

3. Quick note
This talk is not only for developers.
Knowing how code should look like is important to
judge it’s quality.

4. Bad code can bring your company down

5. Clean code
Some parts of this presentation are
from the book “Clean Code” from
Robert C. Martin aka Uncle Bob

6. So what is clean code?

7. – Bjarne Stroustrup, inventor of C++
“I like my code be elegant and efficient”
“Clean code does one thing well”
Elegance

8. – Grady Booch, author of Object Oriented Analysis
and Design With Applications
“Clean code is simple and direct”
“Clean code reads like well-written prose”
Simple, direct, readable

9. – Dave Thomas, founder of OTI
“Clean code can be read”
“Clean code should be literate”
Literate

10. – Michael Feathers, author of Working Effectively with Legacy Code
“Clean code always looks like it was written by
someone who cares”
Care

11. – Ron Jeffries, author of Extreme Programming Installed
“No duplication, one thing, expressiveness, tiny
abstractions.”
Small, expressive, simple

12. – Ward Cunningham, inventor of Wiki, Fit, coinventor of eXtreme
Programming. Motive force behind Design Patterns
“You know you are working on clean code
when each routing you reads turns out to be
pretty much what you expected.”
What you expected

14. Variables, functions and methods

15. Meaningful names
• Intention-Revealing Names
• English Readability -> is_user_logged_in()
• Avoid disinformation
• Use pronounceable names

16. Meaningful names
• Classes should have a noun or noun phrase names but
should not be a verb
• Method names should have verb or verb phrase names
• Use descriptive names

17. The code
• Should be very small!
< 150 characters per line and < 20 lines
• Do one thing and do that right
• Limit it to one level of abstraction
• Reading code from top to bottom
• The ideal number of arguments for a function is zero

18. The code
• Don’t use flag arguments
• passing a boolean into a function
• Pass objects as a function argument to reduce the
arguments
• Have no side effect, does what is expected
• Don’t repeat yourself
• Only return data once

19. What does it not mean

20. Having set requirements like PHP 5.4 >
It happens when the functionality is required

21. Using namespaces
Important for projects with a lot of dependencies

22. The use of autoloaders
It could enhances startup time but it’s not the place
to do so

23. Most of WordPress code base
but every release it does get better

24. What does this mean for WordPress?

25. What does this mean for WordPress?
• Follow the WordPress coding standards
• A shared code base is an important aspect for clean code
• Have it prefix with something that is unique

26. What are the violations in WordPress
• A lot of global variables
• Functions/Methods should never echo
• Returning WP_Error instead of exceptions
• WP_DB

27. Last but not least
Test Driven Development: Unit Tests

28. The three laws of Test Driven Development
• First law
You may not write production code until you have written
a failing unit test
• Second law
You may not write more of a unit test than is sufficient to
fail, and not compiling is failing
• Third law
You may not write more production code than is sufficient
to pass the currently failing test

29. Unit tests is the best documentation of your code
It shows how you intended your code to be used

30. Keep test clean with the same standards as your
production code.

31. Readability is key
Maybe even more important then
your production code

32. A single unit test should contain
• Single concept per test
• One assert per test is a good guideline
• Five other rules: F.I.R.S.T
• Fast
• Independent
• Repeatable
• Self-Validating
• Timely

33. Clean code & me

34. Clean code & me
• I never studied Computer Science
• I do care about quality and structure
• I refuse to do quick wins or hacks
• Work together with others to become better
• Applying unit tests on existing projects
• A lot of refactoring and WTF moments

35. WP_Image_Editor

36. What I have learned from working
together with a Java developer

37. What I have learned from working
together with a Java developer
• Start applying all the things I discussed
• Using OOP more then just wrapping functions in a class
• Using a Wrapper / Decorator pattern
• Think more in advance how things should work
• And also think what could change

38. An hour discussion about hooks in WordPress

40. Thank you for listening
Questions?
@markoheijnen
markoheijnen.com