The document outlines the "Object Calisthenics" rules for writing good object-oriented code. The rules emphasize qualities like loose coupling, encapsulation, and readability by restricting things like indentation levels, use of else statements, primitive wrapping, number of dots per file, abbreviations, class and method sizes, number of instance variables per class, and getters/setters. The goal is to practice and improve OO design skills by following these guidelines.

1. Object Calisthenics
@krolow

2. WTF?
● code is hard to understand, test and
maintain
● OO will save us!
● it's hard the transaction of paradigms
Procedural --- to --- OOP
● Qualities matters:
○ cohesion
○ loose coupling
○ no redundancy
○ encapsulation
○ testability
○ readability

3. so what is it about?
It's an exercise, a practice to help you to write
good oriented-object code!

4. The RULES
#1 One level of indentation per method
#2 Don't use ELSE keyword
#3 Wrap all primitives and String
#4 First class collections
#5 One dot per file
#6 Don't abbreviate
#7 Keep all entities small
#8 No classes with more than two instances
variable
#9 No getters/setters/properties

5. #RULE1
You shall not ident more than once!

6. #RULE2
You shall not have "else"

7. #RULE3
You shall encapsulate the primitives types
not totally applicable in PHP because of performance issues
but... we can do this with other types...

8. #RULE4
Your collection shall not have other members
variable

9. #RULE 5
You shall use one dot per file, so you know
each object has the responsible
not totally applicable in PHP...
... but nested calls
● show some problems of encapsulation
make harder to debug
...
● we can use...
in chain of get and setters
in chain of objects with a fluent interface

10. #RULE 6
You must not abbreviate
why I should abbreviate?
● because I use the name several times...
● .... maybe your method is to heavily and you should remove
duplication
● or because the names are too long...
● ... maybe you are misplacing responsibilities or there is a missing
class...
Avoid also duplicate of words...

11. #RULE 7
Keep your entity classes smaller!
50 rows by class
10 classes by package...
maybe 100 rows by class and 15 by package it's also OK!

12. #RULE 8
Class shall have less than 2 instance variables
Yep quite hard this... but let's try...
with this we can decomposition, we can separate the concerns...
maybe 5 variables it's also okay don't you think?

13. #RULE 9
You shall not have getter and setters
WTF?
Yeah, PHP it's not possible apply that :|
BUT...
If we apply the #RULE 8 we may get this!