I love Ruby! But as in any relationship, to love means that you (often) have to accept the “dark side” too! Ruby is human in nature and has a lot of gotchas, tricks, wierdness and sometimes scary features that I plan to highlight. This talk aims to provide the “Ah-ha!” moments when working in Ruby. This talk is for beginners and experts alike – in fact, I tag slides to mark their level and beginners can choose to tune out of the heavy stuff!

1. The Dark Side of Ruby
http://www.flickr.com/photos/sashapo/2722924752/sizes/l/

2. The Dark Side of Ruby
@gautamrege!
@joshsoftware
http://www.flickr.com/photos/sashapo/2722924752/sizes/l/
since 2007

3. What’s the talk about?
•
Nothing scary
•
Weirdness and Gotcha’s
Ah-ha! Moments

4. Slides are Tagged
Beginner
Expert

5. (In)Famous Infinity
http://www.flickr.com/photos/emdot/482622478/sizes/l/

6. (In)famous Infinity
$ irb> 1/0
=> ZeroDivisionError: divided by 0
$ irb> 1.0/0
=> Infinity
$ irb> Infinity
=> NameError: uninitialized constant
Infinity

7. Base Jumping
http://www.flickr.com/photos/shahdi/8035647153/sizes/l/

8. Base Conversions
$ irb> 12345.to_s(8)
=> "30071"
# => Octal
$ irb> 12345.to_s(36)
=> "9ix"
# That is an actual number
$ irb> 1234.to_s(64)
=> ArgumentError: invalid radix 64

9. The Star - *

10. Splat Expander
Job = Struct.new(:name, :occupation)
tom = Job.new("Tom", "Developer")
name, occupation = *tom
=> ["Tom", "Developer"]
=> name
# "Tom"
=> occupation
# "Developer"

11. Splat Expander
Job = Struct.new(:name, :occupation)
tom = Job.new(occupation: "Developer",
name: "Tom")
name, occupation = *tom
=> name # {:occupation=>"Developer", :name=>
"Tom"}
=> occupation
# nil

12. Hashes and Arrays
a=[1,2,3,4,5,6]!
h=Hash[*a]
=> {1=>2, 3=>4, 5=>6}
[1,2,3] * 3!
=> [1,2,3,1,2,3,1,2,3]
[1,2,3] * "%"!
=> "1%2%3"

13. Calling out to Stabby
blk = ->(f, *m, sl, l) do
puts sl
end
blk.call(1, 2, 3, 4, 5, 6)
=> 5
blk.(1, 2, 3, 4, 5, 6)
=> 5
call is implied for a stabby
proc or a Proc

14. The Case Statement
def multiple_of(factor)!
Proc.new {|p| p.modulo(factor).zero?}!
end!
!
number = 9!
case number!
when multiple_of(3)!
puts "Multiple of 3"!
when multiple_of(7)!
puts "Multiple of 7"!
end

15. Behind every case is a ===
number = 9!
case number !
when multiple_of(3)
Proc.new {|p| p.modulo(3).zero?} === 9
Proc#=== is an alias to Proc#call.
Proc.new { |p| !
p.modulo(3).zero?!
}.call(9)

16. Override the === method
to customise case
evaluation.

17. ==, ===, eql?, equal?
http://www.flickr.com/photos/gak/2418146934/sizes/o/

18. ==, ===, eql?, equal?
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality
irb> 1.eql? 1.0
=> false # equality by value
irb> 1.equal? 1.0
=> false # object identity
irb> 'a'.equal? 'a'
=> false # gotcha!

19. Proc#curry
http://www.flickr.com/photos/miscdebris/6748016253/sizes/o/

20. 3 Pulls for the Jackpot
jackpot = lambda { |x, y, z|
(x == y) == (x == z)
}
!
# 3 pulls
pull = jackpot.curry[rand(5)]
2.times { pull = pull.curry[rand(5)] }
!
p pull ? "Jackpot" : "Sucker!"

21. The curry recipe
pull = jackpot.curry[rand(5)]
=> #<Proc:0x007f9eec0990b0 (lambda)>
•
Return lambda till all parameters are passed.
•
Evaluate the block if all parameters are passed.
2.times { pull = pull.curry[rand(5)] }
=> true # or false

22. So! So you think you can tell…
Protected from Private

23. Private methods
class Base
private
def foo
puts "inside foo"
end
Private Methods are
end
inherited!
class Child < Base
def bar
foo
end
end

24. The elusive include
class Base!
include Mongoid::Document!
end
Private method!
Instance method !
Defined the class Module

25. Protected methods
•
Work with objects not classes.
•
Invoke a protected method on
another object in the same lineage
What the …

26. class Autobot
def initialize(nick); @nick = nick; end
!
protected
attr_accessor :nick
end
!
prime = Autobot.new("Optimus Prime")
p prime.nick
protected method `nick' called for
#<Autobot:0x007f92ba082330 @nick="Optimus
Prime"> (NoMethodError)

27. class Autobot
def fights(target)
p "I am #{self.nick}"
p "Kicking #{target.nick}'s ass"
end
protected
attr_accessor :nick
end
!
prime = Autobot.new("Optimus Prime")
megatron = Autobot.new('Megatron')
!
prime.fights megatron
"I am Optimus Prime"
"Kicking Megatron's ass"

28. Keywords in Ruby?

29. Keywords - hmm…
class Serious
def true
false
end
def false
true
end
end
die = Serious.new
p "seriously!" if die.false

30. Cherry pick from Modules
module Megatron!
def power!
p "Megatron's super strength"!
end!
!
def evil!
p 'Evil genius'!
end!
end

31. Cherry pick from Modules
class Hanuman!
include Megatron!
end
Hanuman.new.power!
# => "Megatron's super strength"!
Hanuman.new.evil !
# => "Evil genius" # Oh no!

32. Cherry pick from Modules
class Hanuman!
def power!
Megatron.instance_method(:power).!
bind(self).call!
end!
end
Hanuman.new.power!
# => "Megatron's super strength"!
Hanuman.new.evil !
# => undefined method `evil’...>

33. That’s all Folks!
@gautamrege
@joshsoftware