Scottish Ruby Conference - "The Dark Side of Ruby"

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
#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;

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;
include/ruby/missing.h

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

24. Base Conversions

25. Base Conversions

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

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

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

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

30. 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

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
=> ArgumentError: invalid radix 64

33. Splat Expander

34. Splat Expander

35. Splat Expander
Job = Struct.new(:name, :occupation)
tom = Job.new("Tom", "Developer")
name, occupation = *tom

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

37. Splat Expander

38. Splat Expander
Job = Struct.new(:name, :occupation)
tom = Job.new(occupation: "Developer",
name: "Tom")
name, occupation = *tom

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

40. Hashes and Arrays

41. Hashes and Arrays

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

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

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

45. 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]

46. 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] * "%"

47. 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"

48. Calling out to Stabby

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

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

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

52. 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

53. 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

54. 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

55. Syntax

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

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

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

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

60. 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

61. Case Complexity

62. 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

63. 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

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

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

66. 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.

67. 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.

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

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

70. ==, ===, eql?, equal?

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

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

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

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

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

76. ==, ===, eql?, equal?
=> false # equality by value
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality
irb> 1.eql? 1.0

77. ==, ===, eql?, equal?
=> false # equality by value
irb> 1 == 1.0
=> true # generic equality
irb> 1 === 1.0
=> true # case equality
irb> 1.eql? 1.0
irb> 1.equal? 1.0

78. ==, ===, eql?, equal?
=> false # equality by value
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

79. ==, ===, eql?, equal?
=> false # equality by value
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'

80. ==, ===, eql?, equal?
=> false # equality by value
=> 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'

81. ==, ===, eql?, equal?
=> false # equality by value
=> 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

82. ==, ===, eql?, equal?
=> false # equality by value
=> 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

83. Object Ids & Fixnum

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

85. 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

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

87. 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!"

88. 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!"

89. 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!"

90. 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

91. 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

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

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

94. Private methods
class Soldier
private
def ryan
puts "inside private ryan"
end
end
class Movie < Soldier
def name
ryan
end
end

95. Private methods
class Soldier
private
def ryan
puts "inside private ryan"
end
end
class Movie < Soldier
def name
ryan
end
end

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

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

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

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

100. Protected methods

101. Protected methods

102. Protected methods
• Work with objects not classes.

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

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

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

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

107. 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)

108. 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

109. 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

110. 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"

111. 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"

112. Keywords in Ruby?

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

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

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

116. 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")

117. 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")

118. 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")

119. 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)

120. 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")

121. 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")

122. 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")

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")
And we thought parenthesis for
method invocation didn’t matter

124. 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

125. 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

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

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

128. 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

129. 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

130. 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!"

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

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

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

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

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

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

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

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

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

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

141. 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’...>

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

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