1.
Object
Calisthenics
#tac2018 @AgileTorinoConf
Ferdinando Santacroce
@jesuswasrasta

2.
“
2
The word calisthenics comes from
the ancient Greek words kalòs
(καλός), beauty, and sthénos
(σθένος), strength.
@jesuswasrasta #tac2018

3.
“
3
So, here’s an exercise that can help you to
internalize principles of good object-oriented
design and actually use them in real life.
Jeff Bay
@jesuswasrasta #tac2018

4.
4
1. Only one level of indentation per method
@jesuswasrasta #tac2018

5.
5
2. Don’t use ELSE keyword
@jesuswasrasta #tac2018

6.
6
3. Wrap all primitives and strings
@jesuswasrasta #tac2018

7.
7
4. First class collections (1)
@jesuswasrasta #tac2018

8.
8
4. First class collections (2)
@jesuswasrasta #tac2018

9.
9
5. One dot per line
@jesuswasrasta #tac2018

10.
10
6. Don’t abbreviate
@jesuswasrasta #tac2018

11.
11
7. Keep all entities small
@jesuswasrasta #tac2018

12.
12
8. No classes with more than two instance variables
@jesuswasrasta #tac2018

13.
13
9. No getters/setters/properties
@jesuswasrasta #tac2018

14.
14
@jesuswasrasta #tac2018
Time to get stronger!
Setup
TicTacToe Kata
2 pomodoros
Pair programming
TDD
Debriefing, Q&A

15.
15
@jesuswasrasta #tac2018
Board, Row, Circle, Cross?
Too many objects?
Did rules conflicted, sometimes?
Does it felt weird or uncomfortable, maybe?
Debriefing

16.
16
E
n
c
a
p
s
u
l
a
t
i
o
n

17.
17
P
o
l
i
m
o
r
p
h
i
s
m

18.
18
N
a
m
i
n
g

19.
19
1. Only one level of indentation per method
@jesuswasrasta #tac2018
Single Responsibility Principle (S.O.L.I.D.)
Extract method
Extract objects (collaborators)

20.
20
2. Don’t use ELSE keyword
@jesuswasrasta #tac2018
Polymorphism
Behavioral Patterns
Strategy Pattern (set algorithm at runtime)
State Pattern (state machines)

21.
21
3. Wrap all primitives and strings
@jesuswasrasta #tac2018
Primitive Obsession Anti-Pattern:
using primitives to represent domain ideas

22.
22
4. First class collections
@jesuswasrasta #tac2018
Encapsulation:
Any class that contains a collection
should contain no other member variables
Give behaviors related to the collection a home

23.
23
5. One dot per line
@jesuswasrasta #tac2018
Law of Demeter
Only talk with your immediate friends,
don’t talk to strangers
Fluent interfaces allowed

24.
24
6. Don’t abbreviate
@jesuswasrasta #tac2018
Naming
“Clean Code” book, Robert C. Martin, Ch. 2
Meaningful, intention-revealing,
pronounceable, searchable names
Methos name too long?
Maybe it does too many things...

25.
25
7. Keep all entities small
@jesuswasrasta #tac2018
Single Responsibility Principle (again...)
Class with 50 l.o.c, methods with 5
The “class that fits in the monitor” rule
There’s no black & white, it’s all about trade-offs

26.
26
8. No classes with more than two instance variables
@jesuswasrasta #tac2018
High cohesion, low coupling

27.
27
9. No getters/setters/properties
@jesuswasrasta #tac2018
Tell, don’t ask
Feature envy code-smell
(extensive use of another class)
They violates Open/Closed Principle (S.O.L.I.D.)
Anemic Domain anti-pattern

28.
28
Thanks!
Any questions?
You can find me at:
▫ @jesuswasrasta
▫ http://about.me/ferdinando.santacroce