This document introduces Ruby and object-oriented programming concepts using Ruby. It discusses creating classes like Brick and Worker, defining attributes and methods, inheritance with subclasses like YellowBrick and RedBrick, and contains examples of creating and manipulating objects. It also shows containing objects in a Box class, searching through objects in a box, and determining if a number is prime. The document provides resources for learning more about Ruby.

1. First steps in Ruby
MeetUP @ Balabit
March 17, 2010
nucc@balabit.com

2. Reality is just a scope of an artist...

5. Ruby
Yukihiro Matsumoto (1995)
www.meetup.com/budapest-rb

6. Lego

7. Objects
class Brick
end
class Worker
end
class Tree
end
class RoofTile
end

8. Objects
class Brick
end
class Worker
2
end
class Tree
end
class RoofTile
end

9. Objects
class Brick
end
class Worker
2.prim?
2 5
end
class Tree
end
2.upto
class RoofTile
end

10. Objects
class Brick
end
class Worker
2.prim?
2 5
end
nil
class Tree
end
2.upto
class RoofTile
end

11. Objects
class Brick
end
class Worker
2.prim?
2 5
end
nil.nil?
nil
class Tree
end
2.upto
class RoofTile
end

12. Brick objects
class Brick
attr :color
attr :sockets
end

13. Yellow and Red bricks
class YellowBrick < Brick
def initialize
@color = :yellow # @ instance variable (always protected!)
@sockets = 6 # @@ class variable
end
end
class RedBrick < Brick
def initialize
@color = :red
@sockets = 6
end
end

14. Yellow and Red bricks
class YellowBrick < Brick
def initialize
@color = :yellow # @ instance variable (always protected!)
@sockets = 6 # @@ class variable
end
end
> yellowBrick = YellowBrick.new
> redBrick = RedBrick.new
class RedBrick < Brick
def initialize
> p yellowBrick
@color = :red
#<YellowBrick:0x10012ac68
@sockets = 6 @color=:yellow, @sockets=6>
end
end

15. Altering objects
class Brick
attr :color
attr_accessor :sockets
end

16. Altering objects
class Brick
attr :color
attr_accessor :sockets
end attr
class Brick
def color
return @color
end
end
# return is not required!

17. Altering objects
class Brick
attr :color
attr_accessor :sockets
end attr attr_accessor
class Brick class Brick
def color def sockets
return @color @sockets
end end
end def sockets= (value)
@sockets = value
# return is not required! end
end

18. Assigning
class Brick
attr :color
attr_writer :sockets
def sockets= (number)
raise Exception.new("Invalid socket number") if number % 2 != 0
raise Exception.new("Too many sockets") unless number <= 10
@sockets = number
end
end

19. Assigning
class Brick
attr :color
attr_writer :sockets
def sockets= (number)
raise Exception.new("Invalid socket number") if number % 2 != 0
raise Exception.new("Too many sockets") = YellowBrick.new 10
> yellowBrick unless number <=
@sockets = number > yellowBrick.sockets = 4
end > puts yellowBrick.sockets
end #4
> yellowBrick.sockets = 5
# Exception: Invalid socket number

20. Box
class Box
def initialize
@items = []
end
def << (item)
@items << item
end
end

21. Box
class Box
def initialize
@items = [] > box = Box.new
end >
> 1.upto 5 do |number|
def << (item) > brick = YellowBrick.new
@items << item > brick.sockets = number * 2
end > box << brick
end > end
> p box
> #<Box:0x10012a650 @items=
[#<YellowBrick:0x10012a498
@color=:yellow, @sockets=2>,
#<YellowBrick...

22. Box
class Box
def initialize
@items = [] > box = Box.new
end >
> 1.upto 5 do |number|
def << (item) > brick = YellowBrick.new
@items << item > brick.sockets = number * 2
end > box << brick
end > end
#<Box:0x10012a650 @items=
> p box
[#<YellowBrick:0x10012a498 @color=:yellow, @sockets=2>,
> #<Box:0x10012a650 @items=
#<YellowBrick:0x10012a510 @color=:yellow, @sockets=4>,
#<YellowBrick:0x10012a4c0 @color=:yellow, @sockets=6>,
[#<YellowBrick:0x10012a498
#<YellowBrick:0x10012a470 @color=:yellow, @sockets=8>,
@color=:yellow, @sockets=2>,
#<YellowBrick:0x10012a448 @color=:yellow, @sockets=10>]>
#<YellowBrick...

23. Searching
class Box
def search (&block)
@items.each do |item|
yield item
end
end
end

24. Searching
class Box
> box = Box.new
def search (&block)
@items.each do |item| >
yield item > 1.upto 5 do |number|
end > brick = YellowBrick.new
end > brick.sockets = number * 2
end > box << brick
> end
> box.search do |brick|
> puts “#{brick.sockets} “
> end
# 2 4 6 8 10

25. Searching
class Box
> box = Box.new
def search (&block)
@items.each do |item| >
yield item > 1.upto 5 do |number|
end > brick = YellowBrick.new
end > brick.sockets = number * 2
end > box << brick
> end
> box.search do |brick|
> puts “#{brick.sockets} “
> end
# 2 4 6 8 10

26. How to start...
apt-get install ruby
apt-get install irb
apt-get install rubygems (11345 packages)
gem install rails
gem install SyslogLogger
gem install hpricot

27. More information...
http://www.ruby-lang.org
http://www.rubygems.org
http://TryRuby.org

28. 2.prim?
class Integer
def prim?
myValue = self.to_i
return false if myValue == 1
2.upto myValue-1 do | i |
return false if (myValue % i) == 0
end
return true
end
end

29. 2.prim?
Q
ue
class Integer
st
def prim?
io
myValue = self.to_i
return false if myValue == 1 ns
2.upto myValue-1 do | i |
?
return false if (myValue % i) == 0
end
return true
end
end

30. Thank you!