Introduction to Object Oriented Design in Ruby for the February 2010 NHRuby (http://nhruby.org) meeting.

1. Object Oriented
Design in Ruby
Brian Turnbull
NHRuby

2. Phone
Concrete Clock
Lamp
Stack
Abstract Mutex
Message

3. Class
Instantiation
Object

4. Class.new
Initialize
Object Instance

5. class CloneTrooper
def march
...
end
end
trooper = CloneTrooper.new
trooper.march

6. Abstraction
Encapsulation
Inheritance
(Hierarchy)
Polymorphism
(Dynamic Binding)

7. Abstraction
Encapsulation
Inheritance
(Hierarchy)
Polymorphism
(Dynamic Binding)

8. Interface
Implementation

9. Stack
E E
Push Pop
E
D D D
C C C
B B B
A A A

10. Leaky Stack
F
E Push
Push
E F
D D E
C C D
B B C
A A B
Discard
A

11. class LeakyStack
def initialize(size)
@size = size
@stack = Array.new
end
def push(item)
@stack.push(item)
@stack.shift if @stack.size > @size
end
def pop
@stack.pop
end
end

12. class LeakyStack
def initialize(size)
@size = size
@stack = Array.new
end
def push(item)
@stack.push(item)
@stack.shift if @stack.size > @size
end
def pop
@stack.pop
end
end

13. class LeakyStack
def initialize(size)
@size = size
@stack = Array.new
end
def push(item)
@stack.push(item)
@stack.shift if @stack.size > @size
end
def pop
@stack.pop
end
end

14. Abstraction
Encapsulation
Inheritance
(Hierarchy)
Polymorphism
(Dynamic Binding)

15. Abstraction
Encapsulation
Inheritance
(Hierarchy)
Polymorphism
(Dynamic Binding)

17. class LeakyStack
def initialize(size)
@size = size
@stack = Array.new
end
def push(item)
@stack.push(item)
discard_overflow
end
def pop
@stack.pop
end
private
def discard_overflow
@stack.shift if @stack.size > @size
end
end

18. class LeakyStack
def initialize(size)
@size = size
@stack = Array.new
end
def push(item)
@stack.push(item)
discard_overflow
end
def pop
@stack.pop
end
private
def discard_overflow
@stack.shift if @stack.size > @size
end
end

19. class LeakyStack
def initialize(size)
@size = size
@stack = Array.new
end
def push(item)
@stack.push(item)
discard_overflow
end
def pop
@stack.pop
end
private
def discard_overflow
@stack.shift if @stack.size > @size
end
end

20. Abstraction
Encapsulation
Inheritance
(Hierarchy)
Polymorphism
(Dynamic Binding)

21. Abstraction
Encapsulation
Inheritance
(Hierarchy)
Polymorphism
(Dynamic Binding)

22. Bicycle
Motorcycle

23. class LeakyStack < Array
def initialize(size)
@stack_size = size
super()
end
def push(item)
super(item)
discard_overflow
end
private
def discard_overflow
shift if size > @stack_size
end
end

24. class LeakyStack < Array
def initialize(size)
@stack_size = size
super()
end
def push(item)
super(item)
discard_overflow
end
private
def discard_overflow
shift if size > @stack_size
end
end

25. class LeakyStack < Array
def initialize(size)
@stack_size = size
super()
end
def push(item)
super(item)
discard_overflow
end
private
def discard_overflow
shift if size > @stack_size
end
end

26. Abstraction
Encapsulation
Inheritance
(Hierarchy)
Polymorphism
(Dynamic Binding)

27. Abstraction
Encapsulation
Inheritance
(Hierarchy)
Dynamic Binding
(Polymorphism)

28. Message stack = LeakyStack.new(10)
stack.push(“foo”)
Dynamic Binding
Run Time
class LeakyStack < Array
def push(item)
Method super(item)
discard_overflow
end
end

29. class LeakyStack < Array
def initialize(size)
@stack_size = size
super() Array
end
def push(item)
super(item)
discard_overflow
end
LeakyStack
private
def discard_overflow
shift if size > @stack_size
end
end

30. Abstraction
Encapsulation
Inheritance
(Hierarchy)
Dynamic Binding
(Polymorphism)

31. Class Methods
Composition
Duck Typing
Mixins

32. Class Methods
Composition
Duck Typing
Mixins

33. class Foo
def self.say_woot
puts "woot!"
end
class << self
def raise_roof
2.times {say_woot}
end
end
end
$ Foo.raise_roof
woot!
woot!
$

34. Class Methods
Composition
Duck Typing
Mixins

35. Class Methods
Composition
Duck Typing
Mixins

36. class LeakyStack
def initialize(size)
@size = size
@stack = Array.new
end
def push(item)
@stack.push(item)
@stack.shift if @stack.size > @size
end
def pop
@stack.pop
end
end

37. Class Methods
Composition
Duck Typing
Mixins

38. Class Methods
Composition
Duck Typing
Mixins

40. def read_file(stream)
stream.read if stream.is_a?(File)
end
def read_file(stream)
stream.read if stream.respond_to(:read)
end

41. Class Methods
Composition
Duck Typing
Mixins

42. Class Methods
Composition
Duck Typing
Mixins

44. Class Methods
Composition
Duck Typing
Mixins

45. The Complete
Class

46. Programming
Exercise

47. 1 2 3
4 5 6
7 8

48. Solve It!
3 8
6 7 1
5 2 4
git://github.com/bturnbull/tile_puzzle.git

49. class Puzzle
def initialize(size = 3)
end
def move(dx, dy)
end
def solved?
end
end

50. Photo Credits in Order of Appearance
Untitled, Chaotic Good01,
http://www.flickr.com/photos/chaoticgood01/4037261441/
lego armee, loop_oh,
http://www.flickr.com/photos/loop_oh/3319379875/
Parliment Clock, Aldaron,
http://www.flickr.com/photos/aldaron/536362686/
Gears and Wheels, pietroizzo,
http://www.flickr.com/photos/pietroizzo/481609998/
Keeping Sound Transit under control, Oran Viriyincy,
http://www.flickr.com/photos/viriyincy/3412876205/
Chrissy's Toei Mixte, "A Touring Bicycle" Final Build, WillJL,
http://www.flickr.com/photos/willjl/3664435742/
Motorcycle 1, Custom Motorcycles,
http://www.flickr.com/photos/falconmotorcycles/2448989350/
~ Duck Talk ~, ViaMoi,
http://www.flickr.com/photos/viamoi/3605272991/
339/365 The ol’ pigskin, The Suss-Man (perpetually behind),
http://www.flickr.com/photos/8692813@N06/4162944190/