Ruby for Java minds

My talk in JRubyConf EU 2013

Transcript

1. RUBY
   FOR JAVA MINDS
   

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2. $ whoami
   

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3. @janogonzalez
   

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4. @hop_in
   

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5. HISTORY
   

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6. THE 90’S
   

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7. BIG
   CHANGES
   

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9. COLD WAR
   IS OVER
   

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11. GRUNGE GOES
    MAINSTREAM
    

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12. APATHY
    

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13. SELF-
    ALIENATION
    

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14. ANGST IS THE NEW
    COOL
    

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15. MEANWHILE IN THE
    PROGRAMMING
    WORLD...
    

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16. RAISING AGAINST
    THE MAINSTREAM
    

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17. JAMES GOSLING
    

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18. JAMES GOSLING
    

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19. JAVA
    

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20. “Write Once,
    Run Anywhere”
    

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21. THE 5 PRINCIPLES
    • It should be "simple, object-oriented and familiar"
    • It should be "robust and secure"
    • It should be "architecture-neutral and portable"
    • It should execute with "high performance"
    • It should be "interpreted, threaded, and dynamic"
    

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22. (THAT WAS NOT RSPEC)
    

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23. MATZ
    

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24. MATZ
    

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25. RUBY
    

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26. “Ruby is designed to make
    programmers happy”
    

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27. MATZ WINS THE
    NOBEL PEACE PRICE
    

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28. (HISTORICAL ACCURACY
    IS OVERRATED)
    

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29. 2 DIFFERENT
    PHILOSOPHIES
    

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30. HOW DO WE
    EMBRACE RUBY?
    

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31. MY HISTORY
    

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32. Y2K
    

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33. COMPUTER APOCALYPSE
    DID NOT HAPPEN
    

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34. I WENT TO A “JAVA
    SCHOOL”
    

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35. JAVA EE, SPRING
    AND CUBICLES
    

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36. HEY, RAILS LOOK
    COOL!
    

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37. HEY, THERE IS A
    FLY OVER THERE!
    

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38. (STUPID FLY)
    

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39. THE 10’S
    

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40. RAILS VS JAVA EE
    WAS OVER
    

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41. HEY, RUBY LOOKS
    COOL!
    

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42. WAIT, HOW DO I
    DECLARE AN INTERFACE?
    

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44. THE PROBLEM
    

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45. “The determined Real Programmer can write
    FORTRAN programs in any language.”
    –Ed Post
    

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46. HOW TO WRITE RUBY
    THAT FEELS LIKE RUBY?
    

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47. A ZEN MOMENT
    

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48. ॳ৺
    

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49. BEGINNER’S
    MIND
    

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50. EMPTY YOUR CUP
    

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51. BACK TO BASICS
    

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52. THE KEY TO
    UNDERSTAND RUBY
    

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53. EXPRESSIONS
    +
    OBJECTS
    

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54. SYNTAX IS
    EXPRESSION-ORIENTED
    

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55. “LISP programmers know the value
    of everything and the cost of
    nothing.”
    - Alan Perlis
    

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56. EXPRESSIONS
    def average(a, b)
    (a + b) / 2
    end
    # => nil
    average(10, 2)
    # => 6
    

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57. EXPRESSIONS
    level = case
    when 1..2 then :excellent
    when 3..5 then :normal
    else :bad
    end
    

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58. ALL VALUES ARE
    OBJECTS
    

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59. OBJECTS
    -1.class
    # => Fixnum
    

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60. OBJECTS
    String.object_id
    # => 70138854779960
    

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61. OBJECTS
    nil.nil?
    # => true
    

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62. WO IST DEIN GOTT JETZT
    

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63. MESSAGES
    

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64. MESSAGES
    EVERYWHERE
    

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65. MESSAGES
    40 + 2
    # => 42
    

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66. MESSAGES
    40.+(2)
    # => 42
    

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67. MESSAGES
    40.send(:+, 2)
    # => 42
    

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68. MESSAGES
    ≠
    METHODS
    

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69. MESSAGES
    class AccountProtectionProxy
    def initialize(real_account, owner)
    @subject = real_account
    @owner = owner
    end
    ...
    

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70. MESSAGES
    class AccountProtectionProxy
    ...
    def method_missing(name, *args)
    check_access
    @subject.send(name, *args)
    end
    ...
    end
    

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71. DYNAMIC TYPING
    

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72. FORGET ABOUT
    JAVA INTERFACES
    

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73. JAVA
    public interface Report {
    ReportFile generate();
    }
    

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74. JAVA
    public class PDFReport
    implements Report {
    ....
    }
    

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75. JAVA
    public class CSVReport
    implements Report {
    ....
    }
    

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76. JAVA
    public void print(List reports) {
    if (reports == null) {
    return;
    }
    for (Report r : reports) {
    ReportFile file = r.generate();
    ...
    }
    }
    

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77. DYNAMIC TYPING
    def print(reports)
    [*reports].each do |r|
    file = r.generate
    ...
    end
    end
    

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78. DYNAMIC TYPING
    class PDFReport
    def generate
    ...
    end
    ...
    end
    

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79. DYNAMIC TYPING
    class CVSReport
    def generate
    ...
    end
    ...
    end
    

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80. DYNAMIC TYPING
    class Duck
    def generate
    ...
    end
    ...
    end
    

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81. PROGRAM TO
    INTERFACES, NOT
    TO interface
    

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82. USED
    EVERYWHERE
    

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83. DYNAMIC TYPING
    "Jano in " << "Berlin"
    # => "Jano in Berlin"
    ["Santiago"] << "Berlin"
    # => ["Santiago", "Berlin"]
    

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84. IF YOU REALLY
    NEED TO CHECK...
    

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85. DYNAMIC TYPING
    if report.respond_to?(:generate)
    report.generate
    ...
    else
    ...
    end
    

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86. IF YOU REALLY, REALLY
    NEED TO CHECK...
    

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87. DYNAMIC TYPING
    if report.is_a?(Report)
    report.generate
    ...
    else
    ...
    end
    

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88. DYNAMIC BUT
    NOT WEAK
    

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89. STRONG TYPING
    100 + 'cool'
    # TypeError: String can't be
    coerced into Fixnum
    

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90. TYPE
    CONVERSIONS
    

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91. CONVERSIONS
    100 + 'cool'.to_i
    # => 100
    100 + Integer('cool')
    # ArgumentError: invalid
    value for Integer(): "lala"
    

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92. BLOCKS
    

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93. BLOCKS ARE USED
    & ABUSED IN RUBY
    

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94. PROGRAM LIKE A
    BOSS
    

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95. (LITERALLY)
    

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96. BLOCKS
    (1..100).select { |n| n % 3 == 0 }
    .map { |n| n * 2 }
    .reduce(:+)
    

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97. FLUID CODE
    

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98. BLOCKS
    File.open('my.txt').each do |line|
    puts line if line =~ /jano/
    end
    

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99. BE MORE
    DECLARATIVE
    

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100. BLOCKS
     words.sort do |a, b|
     a.length <=> b.length
     end
     words.min_by? { |w| w.length }
     words.reject { |w| w.length > 8 }
     # etc...
     

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101. EXAMPLE: SELF
     YIELD
     

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102. BLOCKS
     class Job
     def initialize
     yield self if block_given?
     end
     ...
     end
     

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103. BLOCKS
     job = Job.new do |j|
     j.name = 'Print Reports'
     j.user = 'janogonzalez'
     ...
     end
     

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104. EXAMPLE:
     CALLBACKS
     

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105. BLOCKS
     class Job
     def on_finish(&block)
     @end_callback = block
     end
     def execute()
     ...
     @end_callback.call(self) if @end_callback
     end
     end
     

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106. BLOCKS
     job.on_finish do |j|
     puts "Finished job #{j.name}"
     puts "Status: #{j.status}”
     end
     

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107. MIXINS
     

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108. MODULES AS
     MIXINS
     

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109. ADD BEHAVIOR TO
     INSTANCES
     

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110. MODULES
     module Model
     def persist
     ...
     end
     end
     

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111. MODULES
     class User
     include Model
     ...
     end
     

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112. MODULES
     job = User.new('Jano')
     job.persist
     

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113. ADD BEHAVIOR TO
     CLASSES
     

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114. MODULES
     module Findable
     def find_by_id(id)
     ...
     end
     end
     

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115. MODULES
     class User
     extends Findable
     ...
     end
     

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116. MODULES
     user = User.find_by_id(3)
     

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117. METAPROGRAMMING
     

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118. (USE WITH CAUTION)
     

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119. (AKA THE EVAL IS EVIL
     RULE)
     

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120. ACCESSORS
     

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121. ACCESSORS
     class User
     attr_reader :name
     attr_reader :status
     end
     

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122. OPEN CLASSES
     

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123. OPEN CLASSES
     class Range
     def even
     select(&:even?)
     end
     end
     (0..10).even
     # => [2, 4, 6, 8, 10]
     

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124. OPEN CLASSES
     class BuggyClass
     def buggy_method
     # the fix
     ...
     end
     end
     

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125. OPEN CLASSES
     class Job
     alias_method :old_execute, :execute
     def execute
     ...
     old_execute
     end
     end
     

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126. DEFINE METHODS
     

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127. DEFINE METHODS
     obj = User.new
     User.class_eval do
     def represent
     ...
     end
     end
     obj.represent
     

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128. DEFINE METHODS
     User.instance_eval do
     def random
     ...
     end
     end
     User.random
     

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129. SINGLETON
     METHODS
     

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130. SINGLETON METHOD
     obj = Person.new
     class << obj
     def represent
     ...
     end
     end
     obj.represent
     

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131. (A LOT MORE TO
     EXPLORE...)
     

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132. ONE LAST ADVICE
     

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133. कഁ཭
     

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134. SHU
     कഁ཭
     

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135. HA
     कഁ཭
     

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136. RI
     कഁ཭
     

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138. CONCLUSIONS
     

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139. EMBRACE
     DYNAMIC TYPING
     

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140. BE MORE
     DECLARATIVE
     

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141. WRITE LESS DO
     MORE
     

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142. CONVENTIONS AND
     IDIOMS ARE NOT LAWS
     

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143. THERE IS NO TRUE
     PATH
     

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144. ENJOY RUBY!
     (AND JAVA TOO)
     

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145. DANKESCHÖN!
     

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146. ¡MUCHAS
     GRACIAS!
     

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147. IMAGES
     • http://006.shanbara.jp/movie/data/fat1367385194099.jpg
     • http://wfiles.brothersoft.com/n/nirvana-desktop_157301-1600x1200.jpg
     • http://stilestili.com/wp-content/uploads/2013/04/Ryan-
     Gosling2-2048x2560.jpg
     • http://upload.wikimedia.org/wikipedia/commons/thumb/1/14/
     James_Gosling_2008.jpg/1018px-James_Gosling_2008.jpg
     • http://www.flickr.com/photos/john_lam/1910968816/
     

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