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jRubyThe best of both worlds Christopher Spring

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@autonomous

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Confessions of a... Rubyist

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Brief history of

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Yukihiro “Matz” Matsumoto

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Yukihiro “Matz” Matsumoto“I wanted a scripting language that was more powerful than Perl, and more object-oriented than Python...”

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“[We] need to focus on humans, on how humanscare about doing programming... We are the masters. They are the slaves.”

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“I hope to see Ruby help every programmer in the world be productive, and to enjoy programming, and to be happy.This is the primary purpose of Ruby language”

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A primer

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# booleanstruth = truelies = false# Stringsdude = Matzcredo = "#{dude} is nice, so we are nice!"# Numbers42 ** 1353.8 / 919 % 3

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# Arraysbackpack = [6, apple, [true, some_object]]# Hasheshash = { true => He loves me!, dude => Must obey!, backpack => false}# symbolscities = [:paris, :new_york, :johannesburg]

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Wtf is a symbol?

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coders = [ { language => ruby, location => johannesburg }, { language => java, location => port elizabeth }, # ... { language => ruby, location => pretoria }] # vs.coders = [ { :language => ruby, :location => johannesburg }, { :language => java, :location => port elizabeth }, # ... { :language => ruby, :location => pretoria }]

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Cool, what about classes?

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public Class Person { private String firstName, lastName; public Person(String firstName, String lastName){ setFirstName(firstName); setLastName(lastName); } public String getFirstName(){ return firstName; } public String getLastName(){ return lastName; } public String setFirstName(String firstName){ this.firstName = firstName; } public String setLastName(String lastName){ this.lastName = lastName; }}

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class Person attr_accessor :first_name, :last_name def initialize(first_name, last_name) @first_name = first_name @last_name = last_name endend

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class Person attr_accessor :first_name, :last_name def initialize(first_name, last_name) @first_name = first_name @last_name = last_name end endperson = Person.new( Nick, Cave)person.first_name = Slickperson.last_name = Naveputs "#{person.first_name} #{person.last_name}"

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Btw, everything is an Object!

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true.class() # => TrueClassfalse.to_s() # => "false"5.9.floor() # => 53.times{ puts(Hello JUG!) }# => Hello JUG!# => Hello JUG!# => Hello JUG!

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module Earthend

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module Earth class Person attr_reader :first_name, :last_name def initialize(first_name, last_name) @first_name, @last_name = first_name, last_name end endend

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module Earth class Person attr_reader :first_name, :last_name def initialize(first_name, last_name) @first_name, @last_name = first_name, last_name end endend chap = Earth::Person.new(Chandler, Bing) chap.first_name # => Chandler

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module RepublicPersonnel def storm_trooper Earth::Person.new(Storm, Trooper) endendclass CloningVat extend RepublicPersonnelend

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module RepublicPersonnel def storm_trooper Earth::Person.new(Storm, Trooper) endendclass CloningVat extend RepublicPersonnelend#<Earth::Person @last_name="Trooper", @first_name="Storm">CloningVat.storm_trooper

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module TehForce def sense ... a disturbance in the force endendmodule Earth class Person include TehForce endend

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module TehForce def sense ... a disturbance in the force endendmodule Earth class Person include TehForce endend farm_boy = Earth::Person.new(Luke, Skywalker) # => ... a disturbance in the force farm_boy.sense

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def some_days( something_happens ) puts The sun rises puts something_happens puts The sun setsenddef other_days( this_happens, and_that_happens) puts The sun rises puts this_happens puts and_that_happens puts The sun setsend some_days I do some work other_days I skip, I read a book

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def some_days( something_happens ) puts The sun rises puts something_happens puts The sun setsend

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def some_days( something_happens ) puts The sun rises puts something_happens puts The sun setsend

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def some_days( something_happens ) puts The sun rises puts something_happens puts The sun setsenddef some_days puts The sun rises yield puts The sun setsendsome_days { puts I go to work }some_days do puts I skip puts I read a bookend

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file = File.open(i <3 ruby.txt, w)file.puts "... i really do!"file.close

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file = File.open(i <3 ruby.txt, w) file.puts "... i really do!" file.closeFile.open(i <3 ruby.txt, w) do |file| file.puts "... i really do!"end

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Rubyists TATFT!describe Calculator do before(:each) do @calc = Calculator.new end context Addition do it returns 10 when adding 5 and 5 @calc.add(5,5).should == 10 end it returns 0 when adding 5 and -5 do @calc.add(5,-5).should == 0 end end # ...end

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Metaprogramming

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class Person def initialize @height, @weight, @hair_color = 6.2, 70kg, brown end %w(height weight hair).each do |property| define_method("#{property}") do i_var = self.instance_eval("@#{property}") i_var.to_s.upcase end end def method_missing(*args, &block) puts "I dont have #{args[0].to_s.gsub(/_/, )}" endendp = Person.newp.my_height # => 6.2p.my_weight # => 70KGp.my_hair_color # => BROWNp.your_car_keys # => I dont have your car keys

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A primer

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or....

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Demo time!!

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Interactive Ruby $ jirb jruby-1.6.7 :001 > require java => true jruby-1.6.7 :001 > #...

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Ackermann

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class Ackermann def self.ack(m, n) return n + 1 if m.zero? return ack(m - 1, 1) if n.zero? ack( m - 1, ack(m, n - 1) ) endend

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include Rubeus::SwingJFrame.new(Ackerizer) do |frame| frame.layout = java.awt.FlowLayout.new @m, @n = JTextField.new(3),JTextField.new(10) JButton.new(->) do start = Time.now @result.text = Ackermann.ack( @m.text.to_i, @n.text.to_i ).to_s puts "#{Time.now - start}" end @result = JTextField.new 10 frame.pack frame.showend

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class Ackermann def self.ack(m, n) return n + 1 if m.zero? return ack(m - 1, 1) if n.zero? ack( m - 1, ack(m, n - 1) ) endend

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class Ackermann def self.ack(m, n) return n + 1 if m.zero? return ack(m - 1, 1) if n.zero? ack( m - 1, ack(m, n - 1) ) endendpublic class Ackermann { public static int ack(int m, int n) { if (m == 0) return n + 1; if (n == 0) return ack(m - 1, 1); return ack(m - 1, ack(m, n - 1)); }}

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include Rubeus::SwingJFrame.new(Ackerizer) do |frame| frame.layout = java.awt.FlowLayout.new @m, @n = JTextField.new(3),JTextField.new(10) JButton.new(->) do start = Time.now @result.text = Java::Ackermann.ack( @m.text.to_i, @n.text.to_i ).to_s puts "#{Time.now - start}" end @result = JTextField.new 10 frame.pack frame.showend

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Method overloadingpublic class OverloadTypeChecker { public static String inspect(long value) { return "long"; } public static String inspect(String value) { return "string"; } public static String inspect(Object value) { return "object"; }}

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require javajava_import OverloadTypeChecker do OTCend# jRuby happily handles the simple caseOTC.inspect(5) # longOTC.inspect(Helloooo!) # stringOTC.inspect([]) # object

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public class BitLength { public int neededFor(int i) { return 32; } public int neededFor(long l) { return 64; }}

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# jRuby can be forced to use a specific overloadrequire javajava_import BitLengthbits = BitLength.newbits.needed_for(1_000_000) # 64

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# jRuby can be forced to use a specific overloadrequire javajava_import BitLengthbits = BitLength.newbits.needed_for(1_000_000) # 64# java_sendbits.java_send :neededFor, [Java::int], 1_000_000 # 32

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# jRuby can be forced to use a specific overloadrequire javajava_import BitLengthbits = BitLength.newbits.needed_for(1_000_000) # 64# java_sendbits.java_send :neededFor, [Java::int], 1_000_000 # 32# java_aliasclass BitLength java_alias :needed_for_int, :neededFor, [Java::int]endbits.needed_for_int 1_000_000 # 32

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# jRuby can be forced to use a specific overloadrequire javajava_import BitLengthbits = BitLength.newbits.needed_for(1_000_000) # 64# java_sendbits.java_send :neededFor, [Java::int], 1_000_000 # 32# java_aliasclass BitLength java_alias :needed_for_int, :neededFor, [Java::int]endbits.needed_for_int 1_000_000 # 32# java_methodneeded = bits.java_method :neededFor, [Java::int]needed.call 1_000_000 # 32

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... and more about types

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public class TypeChecker{ public static String check(Object o){ return o.getClass().getName(); }}require javaruby_array = [1, 2, Mushrooms, :sample]java_array = ruby_array.to_java# org.jruby.RubyArrayJava::TypeChecker.check( ruby_array )# [Ljava.lang.Object;Java::TypeChecker.check( java_array )# org.jruby.RubyArrayJava::TypeChecker.check( java_array.to_a )

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Sooo, what about those C extensions... ?

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Awesome, but why?• Cross platform GUI dev• Performance• Ruby interface to legacy code• Use a ruby test framework (Seriously, they’re amazing!)• Utilize java libraries• Sneak ruby into a java shop• Threading

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import org.jruby.embed.InvokeFailedException;import org.jruby.embed.ScriptingContainer;public class RubyFromJava { public static void main(String[] args) { ScriptingContainer container = new ScriptingContainer(); container.runScriptlet("puts Java touched my Ruby"); }} $ java -cp jruby-complete.jar:. RubyFromJava Java touched my Ruby

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More Demos!!

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http://pragprog.com/book/jruby/using-jruby

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http://www.meetup.com/Code-Coffee-JHB/

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http://www.meetup.com/RubyOnBeer/

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Questions?