1. The Ruby Object Model
a presentation for the Nashville Software School
24 June, 2013

2. WHOAMI?
● Max Beizer => jr. developer @ Centresource
● NSS Cohort One graduate
● maxbeizer on:
○ twitter
○ github
○ irc

3. Credit Where Credit is Due...
Practical Object-Oriented
Design in Ruby
Metaprogramming Ruby
Paolo PerrottaSandi Metz

4. Credit Where Credit is Due...
Eliza Brock
elizabrocksoftware.com

5. Ruby and Objects
In Ruby, everything is an object.*
* except when it isn't

6. see also: ancestors

7. Every Object "Returns to the Source"
BasicObject

8. Why do I care?

9. Why do I care?
Why does salutations respond to length and reverse, but not foo?

10. Remember:

11. ruby-doc.org -- String

12. ruby-doc.org -- String
no love for foo
:(

13. salutations
salutations.foo def foo
end

14. salutations
salutations.foo def foo
end

15. salutations
salutations.foo def foo
end
String
Object
BasicObject
def foo
end
def foo
end
def foo
end

16. salutations
salutations.foo def foo
end
String
Object
BasicObject
def foo
end
def foo
end
def foo
end
NoMethodError

17. Impress Your Friends:
Lookup what method_missing does.

18. salutations
salutations.foo def foo
end
String
Object
BasicObject
def foo
end
def foo
end
def foo
end
NoMethodError
+
method_missing

19. This Guy Says:
"Doesn't this make Ruby soooo much slower
than #{my favorite compiled language}?"

20. My Retort:
Moving on...

21. salutations
salutations.length def length
end

22. salutations
salutations.length def foo
end
String
Object
BasicObject
def length
end
salutations.length == 13

23. Uncle Max's Story Time...

24. Inheritance
or how I learned to stop worrying and love method lookup

25. A Simple Ruby Class: You

26. It's Alive!!!!!1

27. you == NSS Student
me != NSS Student
eliza != NSS Student

28. you == NSS Student
me == junior dev
eliza == accomplished professional

29. You
Me
Eliza
We All Have:
● name
● experience
● job(?)

30. Naïve Implementation
(A.K.A. my middle names)
D.R.Y. ?

31. Naïve Implementation
(A.K.A. my middle names)
D.R.Y.
Sopping wet

32. Naïve Implementation
(A.K.A. my middle names)
What if the requirements
changed and "experience"
were henceforth to be known
as "awesome_points" ...?
What about specialization?
Why have three classes that
do the same thing?

33. Inheritance Is All About Commonality
● Share common methods, attributes to keep it DRY
● Generalization vs. Specialization
● Abstract vs. Concrete
use the object model/lookup

35. Specialization
Same Method Name, Different Result
Different Methods

36. Generalization
NssStudent is a ...?
JrDev is a ...?
AccomplishedProfessional is a ...?

37. it fits!!!!!!!1
win

38. shared, generalized code
extracted/abstracted
specialized code
call to super
invokes the method in the super class
overrides the superclass

39. The Abstract Class in Inheritance
part of the lookup chain
generally never to be instantiated on its own

40. Inheritance: is it right for you?
Is it right for your problem set?
Ask yourself: is this an isa?

41. Inheritance: is it right for you?
Is it right for your problem set?
caveat emptor
developer-or

42. Inheritance: is it right for you?
Is it right for your problem set?
put another way: not everything is a nail

43. Rails-Colored Glasses

44. Way back when I was first learning Ruby
(pause for laughter)
Modules
were all like:

45. Nowadays
Modules
are all like:

46. SoftWhere Co. App.

47. SoftWhere Co. App.

48. SoftWhere Co. App.

49. SoftWhere Co. App.
Officeable's methods become instance
methods for the Executive,
MiddleManagement, and Developer
models.
win

50. SoftWhere Co. App.
All three methods have a single,
authoritative place where they live.
That's D.R.Y.
win

51. SoftWhere Co. App.
not so much
What if I create a
new class that needs
to include Officeable
but I forget about or
don't know about
'amount_of_unease'
???

52. SoftWhere Co. App.
win
The next developer
receives a helpful
error message.
Novel concept.

53. SoftWhere Co. App.
Side note: you'll probably want to add a guard to make sure
amount_of_unease is not zero.

54. A Rails Template Pattern
Erich Gamma, Richard Helm, Ralph Johnson and John Vlissides

55. Make sure lib is in the load path

56. image credits:
● http://www.newgre.org/admissions/applying-doctoral-programs-it%E2%80%99s-match/attachment/square-peg-in-a-round-
hole/
● amazon.com
● elizabrocksoftware.com
● http://www.hsxdude.com/
● http://pragdave.pragprog.com/pragdave/2007/05/rails_is_love.html
● http://creepypasta.wikia.com/wiki/File:Creepy-van.jpg
● http://juliasetssail.blogspot.com/2010_04_01_archive.html
● http://knowyourmeme.com/memes/haters-gonna-hate
● http://blog.ausweb.com.au/system-administrator-appreciation-day/
● http://worldtruth.tv/philosophy-the-matrix-return-to-the-source/
the preceding presentation is intended for educational purposes only and should not be viewed
by anyone anywhere, in perpetuity, throughout the universe