The document discusses some of the stereotypes and misconceptions about the Ruby programming language, as well as demonstrating some of Ruby's features through examples in IRB (Interactive Ruby). It notes that while Ruby is often considered easy to use and elegant, it also has some quirks or unexpected behaviors that can surprise newcomers. The document aims to illustrate both the benefits of Ruby as well as some of its less intuitive aspects.

1. Почему все так любят
ruby?
Юрий Хрусталев, Deep Refactoring, 28.09.2016

2. О чем это?
● О стереотипах
● ruby - удобно, элегантно, просто, понятно
● ruby - инструмент Силиконовой Долины
● ruby лучше, чем python*

3. Почему?
● Я недавно начал писать на ruby on rails
● До этого я 4 года писал на python
● Wat?
https://www.destroyallsoftware.com/talks/wat

4. Плохая Махачкала Ruby

5. class Foo
def initialize
puts 'hi'
end
end

6. class Foo
def initialize
puts 'hi'
end
end
Foo.new
# А почему метод initialize, не new?

7. irb(main):001:0> bool

8. irb(main):001:0> bool
NameError: undefined local variable or method
`bool' for main:Object
from (irb):1
from /usr/bin/irb:12:in `<main>'
# Ок, это же язык с продвинутым ООП

9. irb(main):002:0> "".to_b

10. irb(main):002:0> "".to_b
NoMethodError: undefined method `to_b' for
"":String
from (irb):1
from /usr/bin/irb:12:in `<main>'
# Где метод у объекта, это же ООП язык?

11. irb(main):003:0> !!""

12. irb(main):003:0> !!""
(irb):2: warning: string literal in condition
=> true
# Почему warning?
# Нужно сравнивать через ==

13. irb(main):003:0> !!""
(irb):2: warning: string literal in condition
=> true
# Почему warning?
# Нужно сравнивать через ==
# Почему оно true?

14. irb(main):004:0> !!{}

15. irb(main):004:0> !!{}
=> true

16. irb(main):004:0> !!{}
=> true
irb(main):005:0> !![]

17. irb(main):004:0> !!{}
=> true
irb(main):005:0> !![]
=> true

18. irb(main):004:0> !!{}
=> true
irb(main):005:0> !![]
=> true
irb(main):006:0> !!Object.new

19. irb(main):004:0> !!{}
=> true
irb(main):005:0> !![]
=> true
irb(main):006:0> !!Object.new
=> true
# Ничто не false, кроме false/nil/собственного ==

20. # Ruby? Это такой DSL для написания Rails-приложений?
irb(main):001:0> require 'active_support/all'
=> true

21. # Ruby? Это такой DSL для написания Rails-приложений?
irb(main):001:0> require 'active_support/all'
=> true
irb(main):002:0> [].blank?

22. # Ruby? Это такой DSL для написания Rails-приложений?
irb(main):001:0> require 'active_support/all'
=> true
irb(main):002:0> [].blank?
=> true

23. # Ruby? Это такой DSL для написания Rails-приложений?
irb(main):001:0> require 'active_support/all'
=> true
irb(main):002:0> [].blank?
=> true
irb(main):003:0> nil.blank?

24. # Ruby? Это такой DSL для написания Rails-приложений?
irb(main):001:0> require 'active_support/all'
=> true
irb(main):002:0> [].blank?
=> true
irb(main):003:0> nil.blank?
=> true

25. # Ruby? Это такой DSL для написания Rails-приложений?
irb(main):001:0> require 'active_support/all'
=> true
irb(main):002:0> [].blank?
=> true
irb(main):003:0> nil.blank?
=> true
irb(main):004:0> 0.blank?

26. # Ruby? Это такой DSL для написания Rails-приложений?
irb(main):001:0> require 'active_support/all'
=> true
irb(main):002:0> [].blank?
=> true
irb(main):003:0> nil.blank?
=> true
irb(main):004:0> 0.blank?
=> false

27. # Ruby? Это такой DSL для написания Rails-приложений?
irb(main):001:0> require 'active_support/all'
=> true
irb(main):002:0> [].blank?
=> true
irb(main):003:0> nil.blank?
=> true
irb(main):004:0> 0.blank?
=> false
# нормально же общались

28. # Python
>>> arr = [1, 2, 3]
>>> map(str, arr)
["1", "2", "3"]

29. irb(main):001:0> arr = [1, 2, 3]
=> [1, 2, 3]

30. irb(main):001:0> arr = [1, 2, 3]
=> [1, 2, 3]
irb(main):002:0> arr.map {|item| item.to_s}
=> ["1", "2", "3"]

31. irb(main):001:0> arr = [1, 2, 3]
=> [1, 2, 3]
irb(main):002:0> arr.map {|item| item.to_s}
=> ["1", "2", "3"]
irb(main):003:0> arr.map(&:to_s)
=> ["1", "2", "3"]
# &: - указатель на имя метода

32. irb(main):001:0> arr = ["1", "2", "3"]
=> ["1", "2", "3"]

33. irb(main):001:0> arr = ["1", "2", "3"]
=> ["1", "2", "3"]
irb(main):002:0> arr.map(&:String.new)

34. irb(main):001:0> arr = ["1", "2", "3"]
=> ["1", "2", "3"]
irb(main):002:0> arr.map(&:String.new)
NoMethodError: undefined method `new' for
:String:Symbol
from (irb):26
from /usr/bin/irb:12:in `<main>'
# это было бы слишком элегантно

35. irb(main):003:0> arr.map(&String.method(:new))

36. irb(main):003:0> arr.map(&String.method(:new))
=> ["1", "2", "3"]
# это удобно

37. # chain.rb
x =
' foo bar '
.strip
.split(' ')
puts x.to_s

38. # chain.rb
x =
' foo bar '
.strip
.split(' ')
puts x.to_s
irb(main):001:0> load './chain.rb'
[1, 2]
=> nil

39. # chain.rb
x =
' foo bar '
#.strip
.split(' ')
puts x.to_s

40. irb(main):001:0> load './chain.rb'
SyntaxError: /tmp/code.rb:4: syntax error,
unexpected '.', expecting end-of-input
.split(' ')
^
from (irb):15:in `load'
from (irb):15
from /usr/bin/irb:12:in `<main>'
# даже python так не делает

41. irb(main):001:0> String.new "x"

42. irb(main):001:0> String.new "x"
=> "x"

43. irb(main):001:0> String.new "x"
=> "x"
irb(main):002:0> String.new("x")

44. irb(main):001:0> String.new "x"
=> "x"
irb(main):002:0> String.new("x")
=> "x"

45. irb(main):001:0> String.new "x"
=> "x"
irb(main):002:0> String.new("x")
=> "x"
irb(main):003:0> String.new( "x" )

46. irb(main):001:0> String.new "x"
=> "x"
irb(main):002:0> String.new("x")
=> "x"
irb(main):003:0> String.new( "x" )
=> "x"

47. irb(main):001:0> String.new "x"
=> "x"
irb(main):002:0> String.new("x")
=> "x"
irb(main):003:0> String.new( "x" )
=> "x"
irb(main):004:0> String.new ("x")

48. irb(main):001:0> String.new "x"
=> "x"
irb(main):002:0> String.new("x")
=> "x"
irb(main):003:0> String.new( "x" )
=> "x"
irb(main):004:0> String.new ("x")
=> "x"

49. irb(main):005:0> [String.new("x")]

50. irb(main):005:0> [String.new("x")]
=> ["x"]

51. irb(main):005:0> [String.new("x")]
=> ["x"]
irb(main):006:0> [String.new ("x")]

52. irb(main):005:0> [String.new("x")]
=> ["x"]
irb(main):006:0> [String.new ("x")]
SyntaxError: (irb):25: syntax error, unexpected (
arg, expecting ']'
[String.new ("x")]
^
(irb):25: syntax error, unexpected ']',
expecting end-of-input
from /usr/bin/irb:12:in `<main>'
# Пробелы

53. irb(main):001:0> %w(rm -rf /home)

54. irb(main):001:0> %w(rm -rf /home)
=> ["rm", "-rf", "/home"]

55. irb(main):001:0> %w(rm -rf /home)
=> ["rm", "-rf", "/home"]
irb(main):002:0> %i(rm -rf /home)

56. irb(main):001:0> %w(rm -rf /home)
=> ["rm", "-rf", "/home"]
irb(main):002:0> %i(rm -rf /home)
=> [:rm, :"-rf", :"/home"]

57. irb(main):001:0> %w(rm -rf /home)
=> ["rm", "-rf", "/home"]
irb(main):002:0> %i(rm -rf /home)
=> [:rm, :"-rf", :"/home"]
irb(main):003:0> %x(rm -rf /home)

58. irb(main):001:0> %w(rm -rf /home)
=> ["rm", "-rf", "/home"]
irb(main):002:0> %i(rm -rf /home)
=> [:rm, :"-rf", :"/home"]
irb(main):003:0> %x(rm -rf /home)
=> ""
# это еще хорошо у меня OSX

59. irb(main):001:0> {foo: 1}
=> {:foo=>1}

60. irb(main):001:0> {foo: 1}
=> {:foo=>1}
irb(main):002:0> {:foo => 1}
=> {:foo=>1}

61. irb(main):001:0> {foo: 1}
=> {:foo=>1}
irb(main):002:0> {:foo => 1}
=> {:foo=>1}
irb(main):003:0> {"foo" => 1}
=> {"foo"=>1}

62. irb(main):005:0> {:foo => 1}["foo"]

63. irb(main):005:0> {:foo => 1}["foo"]
=> nil

64. irb(main):005:0> {:foo => 1}["foo"]
=> nil
irb(main):006:0> {:foo => 1}["foo".to_sym]

65. irb(main):005:0> {:foo => 1}["foo"]
=> nil
irb(main):006:0> {:foo => 1}["foo".to_sym]
=> 1
# зато метод без скобок вызван

66. irb(main):001:0> h = {:foo => 1}
=> {:foo=>1}

67. irb(main):001:0> h = {:foo => 1}
=> {:foo=>1}
irb(main):002:0> h = h.with_indifferent_access
=> {"foo"=>1}

68. irb(main):001:0> h = {:foo => 1}
=> {:foo=>1}
irb(main):002:0> h = h.with_indifferent_access
=> {"foo"=>1}
irb(main):003:0> h["foo"]

69. irb(main):001:0> h = {:foo => 1}
=> {:foo=>1}
irb(main):002:0> h = h.with_indifferent_access
=> {"foo"=>1}
irb(main):003:0> h["foo"]
=> 1

70. irb(main):001:0> h = {:foo => 1}
=> {:foo=>1}
irb(main):002:0> h = h.with_indifferent_access
=> {"foo"=>1}
irb(main):003:0> h["foo"]
=> 1
irb(main):004:0> h[:foo]

71. irb(main):001:0> h = {:foo => 1}
=> {:foo=>1}
irb(main):002:0> h = h.with_indifferent_access
=> {"foo"=>1}
irb(main):003:0> h["foo"]
=> 1
irb(main):004:0> h[:foo]
=> 1
# доступно только в rails

72. irb(main):001:0> h = {:foo => 1}
=> {:foo=>1}
irb(main):002:0> h = h.with_indifferent_access
=> {"foo"=>1}
irb(main):003:0> h["foo"]
=> 1
irb(main):004:0> h[:foo]
=> 1
# доступно только в rails
# ruby DSL для rails

73. def foo(&block)
puts 'open resource'
[*41..42].each &block.method(:call)
puts 'close resource'
end
foo do |value|
puts value
end

74. def foo(&block)
puts 'open resource'
[*41..42].each &block.method(:call)
puts 'close resource'
end
foo do |value|
puts value
end
> open resource
41
42
close resource

75. def foo(&block)
puts 'open resource'
[*41..42].each &block.method(:call)
puts 'close resource'
end
foo do |value|
puts value
break
end

76. def foo(&block)
puts 'open resource'
[*41..42].each &block.method(:call)
puts 'close resource'
end
foo do |value|
puts value
break
end
> open resource
41

77. def foo(&block)
puts 'open resource'
[*41..42].each &block.method(:call)
puts 'close resource'
end
def has_answer?
foo do |value|
return true if value == 42
end
end
puts has_answer?

78. def foo(&block)
puts 'open resource'
[*41..42].each &block.method(:call)
puts 'close resource'
end
def has_answer?
foo do |value|
return true if value == 42
end
end
puts has_answer?
> open resource
true

79. def foo(&block)
puts 'open resource'
[*41..42].each &block.method(:call)
puts 'close resource'
end
def has_answer?
rc = false
foo {|value| rc = true if value == 42}
rc
end
puts has_answer?

80. def foo(&block)
puts 'open resource'
[*41..42].each &block.method(:call)
puts 'close resource'
end
def has_answer?
rc = false
foo {|value| rc = true if value == 42}
rc
end
puts has_answer?
> open resource
close resource
true

81. module Foo
def bar
puts 'hi'
end
end
irb(main):009:0* Foo.bar

82. module Foo
def bar
puts 'hi'
end
end
irb(main):009:0* Foo.bar
NoMethodError: undefined method `bar' for
Foo:Module
from (irb):9
from /usr/bin/irb:12:in `<main>'

83. module Foo
module_function
def bar
puts 'hi'
end
end
irb(main):010:0* Foo.bar
hi

84. module Foo
BAZ = 'hey'
module_function
def bar
puts 'hi'
end
end

85. module Foo
BAZ = 'hey'
module_function
def bar
puts 'hi'
end
end
irb(main):096:0> Foo::bar

86. module Foo
BAZ = 'hey'
module_function
def bar
puts 'hi'
end
end
irb(main):096:0> Foo::bar
hi
=> nil

87. module Foo
BAZ = 'hey'
module_function
def bar
puts 'hi'
end
end
irb(main):096:0> Foo::bar
hi
=> nil
irb(main):097:0> Foo::BAZ

88. module Foo
BAZ = 'hey'
module_function
def bar
puts 'hi'
end
end
irb(main):096:0> Foo::bar
hi
=> nil
irb(main):097:0> Foo::BAZ
=> "hey"

89. module Foo
BAZ = 'hey'
module_function
def bar
puts 'hi'
end
end
irb(main):096:0> Foo::bar
hi
=> nil
irb(main):097:0> Foo::BAZ
=> "hey"
irb(main):098:0> Foo.baz

90. module Foo
BAZ = 'hey'
module_function
def bar
puts 'hi'
end
end
irb(main):096:0> Foo::bar
hi
=> nil
irb(main):097:0> Foo::BAZ
=> "hey"
irb(main):098:0> Foo.baz
NoMethodError: undefined
method `baz' for Foo:Module
from (irb):98
from /usr/bin/irb:12:in
`<main>'
# почему нет?

91. В качестве заключения, что с
популярностью ruby?

92. http://githut.info/

93. http://pypl.github.io/PYPL.html

94. http://stackoverflow.com/jobs

95. Спасибо за внимание