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, weirdness 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! My talk shall cover the dark side of the following features of Ruby (in no particular order) Keyword wierdness method missing Module inheritance! (huh?) Accessor righteousness Curried Procs for the hungry Base Conversions Cherry picking module methods Oniguruma games Object id weirdness procs, blocks and our friend stabby. ==, ===, eql? and equal? and more… As with most of my talks, humor plays an important role and I shall aim to get everyone high on Ruby with a deep dive!

1. The Dark Side of Ruby
@gautamrege!
@joshsoftware

2. What’s the talk about?

3. What’s the talk about?
• Ruby is AWESOME but …

4. What’s the talk about?
• Ruby is AWESOME but …
• Nothing scary

5. What’s the talk about?
• Ruby is AWESOME but …
• Nothing scary really

6. What’s the talk about?
• Ruby is AWESOME but …
• Nothing scary
• Weirdness and Gotcha’s
really

7. What’s the talk about?
• Ruby is AWESOME but …
• Nothing scary
• Weirdness and Gotcha’s
Ah-ha! Moments
really

8. Slides are Tagged

9. Slides are Tagged
Beginner

10. Slides are Tagged
Expert

11. (In)Famous Infinityhttp://www.flickr.com/photos/emdot/482622478/sizes/l/

12. (In)Famous Infinity

13. (In)Famous Infinity

14. (In)Famous Infinity
$ irb> 1/0

15. (In)Famous Infinity
$ irb> 1/0
=> ZeroDivisionError: divided by 0

16. (In)Famous Infinity
$ irb> 1/0
$ irb> 1.0/0
=> ZeroDivisionError: divided by 0

17. (In)Famous Infinity
$ irb> 1/0
$ irb> 1.0/0
=> ZeroDivisionError: divided by 0
=> Infinity

18. (In)Famous Infinity
$ irb> 1/0
$ irb> 1.0/0
$ irb> Infinity
=> ZeroDivisionError: divided by 0
=> Infinity

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

20. (In)Famous Infinity

21. (In)Famous Infinity

22. (In)Famous Infinity
#if !defined(INFINITY) || !defined(NAN)!
union bytesequence4_or_float {!
unsigned char bytesequence[4];!
float float_value;!
};!
#endif!
!
RUBY_EXTERN const union
bytesequence4_or_float rb_infinity;

23. (In)Famous Infinity
#if !defined(INFINITY) || !defined(NAN)!
union bytesequence4_or_float {!
unsigned char bytesequence[4];!
float float_value;!
};!
#endif!
!
RUBY_EXTERN const union
bytesequence4_or_float rb_infinity;
include/ruby/missing.h

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

25. Base Conversions

26. Base Conversions

27. Base Conversions
$ irb> 12345.to_s(8)

28. Base Conversions
$ irb> 12345.to_s(8)
=> "30071" # => Octal

29. Base Conversions
$ irb> 12345.to_s(8)
$ irb> 12345.to_s(36)
=> "30071" # => Octal

30. Base Conversions
$ irb> 12345.to_s(8)
$ irb> 12345.to_s(36)
=> "30071" # => Octal
=> "9ix" # That is an actual number

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

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

34. Hashes and Arrays

35. Hashes and Arrays

36. Hashes and Arrays
a=[1,2,3,4,5,6]!
h=Hash[*a]

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

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

39. 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]

40. 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] * "%"

41. 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"

42. Calling out to Stabby

43. Calling out to Stabby
blk = ->(f, *m, sl, l) do
puts sl
end

44. Calling out to Stabby
blk = ->(f, *m, sl, l) do
puts sl
end
blk.call(1, 2, 3, 4, 5, 6)

45. Calling out to Stabby
blk = ->(f, *m, sl, l) do
puts sl
end
blk.call(1, 2, 3, 4, 5, 6)
=> 5

46. blk.(1, 2, 3, 4, 5, 6)
Calling out to Stabby
blk = ->(f, *m, sl, l) do
puts sl
end
blk.call(1, 2, 3, 4, 5, 6)
=> 5

47. blk.(1, 2, 3, 4, 5, 6)
Calling out to Stabby
blk = ->(f, *m, sl, l) do
puts sl
end
blk.call(1, 2, 3, 4, 5, 6)
=> 5

48. blk.(1, 2, 3, 4, 5, 6)
=> 5
syntax sugar for call
blk[1,2,3,4,5,6]
Calling out to Stabby
blk = ->(f, *m, sl, l) do
puts sl
end
blk.call(1, 2, 3, 4, 5, 6)
=> 5

49. Syntax

50. Syntax
def foo(a=1, b=1,opts={})
end

51. Syntax
def foo(a: 1, b: 2)
end

52. Syntax
def foo(a: 1, b: 2)
end
keyword arguments

53. Syntax
def foo(a: 1, b:, c: 2)
end
def foo(a: 1, b: 2)
end
keyword arguments

54. Syntax
def foo(a: 1, b:, c: 2)
end
def foo(a: 1, b: 2)
end
keyword arguments

55. Syntax
def foo(a: 1, b:, c: 2)
end
foo(a: 2)
=> ArgumentError: missing keyword: b
Mandatory keyword
arguments
def foo(a: 1, b: 2)
end
keyword arguments

56. Syntax

57. Syntax
def foo(a, b)
p a, b
end

58. Syntax
def foo(a, b)
p a, b
end
foo (1, 2)

59. Syntax
def foo(a, b)
p a, b
end
foo (1, 2)
syntax error, unexpected
',', expecting ')'

60. Syntax
def foo(a, b)
p a, b
end
foo (1, 2)
foo(1, 2)

61. Syntax
def foo(a, b)
p a, b
end
foo (1, 2)
foo(1, 2)

62. Syntax
def foo(a, b)
p a, b
end
foo (1, 2)
foo(1, 2) syntax error, unexpected
',', expecting ')'

63. Syntax

64. Syntax
irb> a[1]
What is the
data type of a ?

65. Syntax
irb> a[1]
a = [ 10, 11, 12] # Array

66. Syntax
irb> a[1]
a = [ 10, 11, 12] # Array
a = { 1 => "one" } # Hash

67. Syntax
irb> a[1]
a = [ 10, 11, 12] # Array
a = { 1 => "one" } # Hash
a = Proc.new { |e| p e }

68. Case Complexity

69. 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

70. 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

71. Behind every case is a ===
number = 9!
case number !
when multiple_of(3)
Proc.new {|p| p.modulo(3).zero?} === 9

72. Behind every case is a ===
number = 9!
case number !
when multiple_of(3)
Proc.new {|p| p.modulo(3).zero?} === 9

73. 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.

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

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

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

77. ==, ===, eql?, equal?

78. ==, ===, eql?, equal?
irb> 1 == 1.0

79. ==, ===, eql?, equal?
irb> 1 == 1.0
=> true # generic equality

80. ==, ===, eql?, equal?
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0

81. ==, ===, eql?, equal?
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality

82. ==, ===, eql?, equal?
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality
irb> 1.eql? 1.0

83. ==, ===, eql?, equal?
=> false # alias of == except Numeric
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality
irb> 1.eql? 1.0

84. ==, ===, eql?, equal?
=> false # alias of == except Numeric
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality
irb> 1.eql? 1.0
irb> 1.equal? 1.0

85. ==, ===, eql?, equal?
=> false # alias of == except Numeric
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality
irb> 1.eql? 1.0
irb> 1.equal? 1.0
=> false # object identity

86. ==, ===, eql?, equal?
=> false # alias of == except Numeric
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality
irb> 1.eql? 1.0
irb> 1.equal? 1.0
=> false # object identity
irb> 'a'.equal? 'a'

87. ==, ===, eql?, equal?
=> false # alias of == except Numeric
=> false # gotcha?
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality
irb> 1.eql? 1.0
irb> 1.equal? 1.0
=> false # object identity
irb> 'a'.equal? 'a'

88. ==, ===, eql?, equal?
=> false # alias of == except Numeric
=> false # gotcha?
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality
irb> 1.eql? 1.0
irb> 1.equal? 1.0
=> false # object identity
irb> 'a'.equal? 'a'
irb> 1.equal? 1

89. ==, ===, eql?, equal?
=> false # alias of == except Numeric
=> false # gotcha?
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality
irb> 1.eql? 1.0
irb> 1.equal? 1.0
=> false # object identity
irb> 'a'.equal? 'a'
=> true # gotcha?
irb> 1.equal? 1

90. Object Ids & Fixnum

91. Object Ids & Fixnum
Fixnum * 2 + 1
irb> 23 * 2 + 1
=> 47
irb > 23.object_id
=> 47

92. Object Ids & Fixnum
Fixnum * 2 + 1
irb> 23 * 2 + 1
=> 47
irb > 23.object_id
=> 47
irb> (2**62 - 1).class
=> Fixnum
irb> (2**62).class
=> Bignum

93. http://www.flickr.com/photos/miscdebris/6748016253/sizes/o/

94. 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!"

95. 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!"

96. 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!"

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

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

99. So! So you think you can tell…
Heaven from Hell
- Pink Floyd

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

101. Private methods
class Soldier
private
def ryan
puts "Saving private ryan"
end
end
class Movie < Soldier
def name
ryan
end
end

102. Private methods
class Soldier
private
def ryan
puts "Saving private ryan"
end
end
class Movie < Soldier
def name
ryan
end
end

103. Private methods
class Soldier
private
def ryan
puts "Saving private ryan"
end
end
class Movie < Soldier
def name
ryan
end
end
Private Methods are
inherited!

104. class Base!
include Mongoid::Document!
end
The elusive include

105. class Base!
include Mongoid::Document!
end
The elusive include

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

107. Protected methods

108. Protected methods

109. Protected methods
• Work with objects not classes.

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

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

112. class Autobot
def initialize(nick); @nick = nick; end
!
protected
attr_accessor :nick
end
!
prime = Autobot.new("Optimus Prime")
p prime.nick

113. class Autobot
def initialize(nick); @nick = nick; end
!
protected
attr_accessor :nick
end
!
prime = Autobot.new("Optimus Prime")
p prime.nick

114. 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)

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

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

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

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

119. Keywords in Ruby?

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

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

122. Keywords - hmm…
class Serious
def true
false
end
def false
true
end
end
die = Serious.new
p "seriously!" if die.false
stack too deep?

123. superlative
class Search!
def search!
p "Default Search algorithm"!
end!
end!
class KeywordSearch < Search !
def search(keyword:)!
super!
end!
end!
KeywordSearch.new.search(keyword: "Ruby")

124. superlative
class Search!
def search!
p "Default Search algorithm"!
end!
end!
class KeywordSearch < Search !
def search(keyword:)!
super!
end!
end!
KeywordSearch.new.search(keyword: "Ruby")

125. superlative
class Search!
def search!
p "Default Search algorithm"!
end!
end!
class KeywordSearch < Search !
def search(keyword:)!
super!
end!
end!
KeywordSearch.new.search(keyword: "Ruby")

126. superlative
class Search!
def search!
p "Default Search algorithm"!
end!
end!
class KeywordSearch < Search !
def search(keyword:)!
super!
end!
end!
KeywordSearch.new.search(keyword: "Ruby")
`search`: wrong number
of arguments (1 for 0)

127. superlative
class Search!
def search!
p "Default Search algorithm"!
end!
end!
class KeywordSearch < Search !
def search(keyword:)!
super()!
end!
end!
KeywordSearch.new.search(keyword: "Ruby")

128. superlative
class Search!
def search!
p "Default Search algorithm"!
end!
end!
class KeywordSearch < Search !
def search(keyword:)!
super()!
end!
end!
KeywordSearch.new.search(keyword: "Ruby")

129. superlative
class Search!
def search!
p "Default Search algorithm"!
end!
end!
class KeywordSearch < Search !
def search(keyword:)!
super()!
end!
end!
KeywordSearch.new.search(keyword: "Ruby")

130. superlative
class Search!
def search!
p "Default Search algorithm"!
end!
end!
class KeywordSearch < Search !
def search(keyword:)!
super()!
end!
end!
KeywordSearch.new.search(keyword: "Ruby")
And we thought parenthesis for
method invocation didn’t matter

131. Module mixins are funny
module Superman!
def fly; p "Superman: It's a bird"; end!
end!
!
module Batman!
def fly; p "Batman: Fly? Me?"; end!
end!
!
module Ironman!
def fly; p "Iroman: That's flying!"; end!
end

132. Module mixins are funny
module Superman!
def fly; p "Superman: It's a bird"; end!
end!
!
module Batman!
def fly; p "Batman: Fly? Me?"; end!
end!
!
module Ironman!
def fly; p "Iroman: That's flying!"; end!
end

133. Module mixins are funny
class Tinyman!
include Superman!
include Batman!
include Ironman!
end!
!
Tinyman.new.fly
"Iroman: That's how you fly!"

134. Module mixins are funny
class Tinyman!
include Superman!
include Batman!
include Ironman!
end!
!
Tinyman.new.fly
"Iroman: That's how you fly!"

135. Module Inheritance?
module Superman!
def fly; p "Superman: It's a bird"; end!
end!
!
module Batman!
def fly; p "Batman: Fly? Me?"; end!
end!
!
module Ironman!
def fly; super; p "Iroman: That's flying!"; end!
end

136. Module Inheritance?
module Superman!
def fly; p "Superman: It's a bird"; end!
end!
!
module Batman!
def fly; p "Batman: Fly? Me?"; end!
end!
!
module Ironman!
def fly; super; p "Iroman: That's flying!"; end!
end

137. Module Inheritance?
module Superman!
def fly; p "Superman: It's a bird"; end!
end!
!
module Batman!
def fly; p "Batman: Fly? Me?"; end!
end!
!
module Ironman!
def fly; super; p "Iroman: That's flying!"; end!
end
"Batman: Fly? Me?”!
"Iroman: That's flying!"

138. Dynamic Inheritance!
class Tinyman!
include Superman!
include Batman!
include Ironman!
end

139. Dynamic Inheritance!
class Tinyman!
include Superman!
include Batman!
include Ironman!
end

140. class Tinyman!
include Superman!
include Ironman!
include Batman!
end
Dynamic Inheritance!
class Tinyman!
include Superman!
include Batman!
include Ironman!
end

141. class Tinyman!
include Superman!
include Ironman!
include Batman!
end
Dynamic Inheritance!
class Tinyman!
include Superman!
include Batman!
include Ironman!
end

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

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

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

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

146. Cherry pick from Modules
class Hanuman!
def power!
Megatron.instance_method(:power).!
bind(self).call!
end!
end

147. Cherry pick from Modules
class Hanuman!
def power!
Megatron.instance_method(:power).!
bind(self).call!
end!
end

148. 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’...>

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

150. That’s all Folks!
@gautamrege
@joshsoftware
since 2007