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An introduction to Ruby

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An introduction to Ruby

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My slides from the presentation I gave at the Devnology Community Day on 7 November 2009.

My slides from the presentation I gave at the Devnology Community Day on 7 November 2009.

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An introduction to Ruby

  1. 1. An Introduction to Ruby
  2. 2. Speaker.new({ :name => "Wes Oldenbeuving", :twitter => "@Narnach", :rubyist_since => "Early 2006", :works_as => "Freelance Rubyist", :code_at => "github.com/Narnach", :email => "wes@narnach.com" })
  3. 3. Overview What is Ruby? History and current versions What does Ruby look like? Basic tools of the Rubyist Practical uses of Ruby The Ruby Community
  4. 4. What is Ruby?
  5. 5. Object oriented
  6. 6. Everything is an object 1.class # => Fixnum 'a'.class # => String :z.class # => Symbol class Foo end Foo.class # => Class Foo.new.class # => Foo
  7. 7. Dynamically typed def foo(bar) bar * 2 end foo(1) # => 2 foo("a") # => "aa"
  8. 8. Duck Typing "a".respond_to? :size # => true 1.respond_to? :+ # => true 1.respond_to? :inject # => false
  9. 9. Scripting language
  10. 10. Everything is an expression
  11. 11. Ruby: the history
  12. 12. Japan
  13. 13. Idea 1993
  14. 14. Productivity and fun
  15. 15. Focus on the programmer, not the computer
  16. 16. Inspired by Perl, Smalltalk, Lisp
  17. 17. v0.95 1995
  18. 18. English-language 1999 v1.3
  19. 19. Programming Ruby 2000
  20. 20. Current versions of Ruby
  21. 21. Matz Ruby Interpreter Stable Ruby 1.8
  22. 22. Yet Another Ruby VM Development Ruby 1.9
  23. 23. JRuby (1.4) Ruby 1.8 (1.9) on the JVM
  24. 24. Rubinius Ruby 1.8 in Ruby (and a bit of C++)
  25. 25. IronRuby (0.9.2) Ruby 1.8 without continuations
  26. 26. MacRuby (0.5) Ruby 1.9 in Objective-C
  27. 27. Maglev Ruby in Gemstone Smalltalk VM
  28. 28. Ruby: the language
  29. 29. What does Ruby look like?
  30. 30. Strings and Variables 'Hello, Devnology!' name = 'Devnology' # => "Devnology" "Hello, #{name}!" # => "Hello, Devnology!"
  31. 31. Methods str = "Hello, Devnology!" str.size # => 17 str.sub("Devnology", "World") # => "Hello, World!" def greet(name="Wes") "Greetings, #{name}!" end puts greet puts greet('Devnology') # >> Greetings, Wes! # >> Greetings, Devnology!
  32. 32. Numbers 1 + 2 # => 3 1 + 2.1 # => 3.1 2**10 # => 1024 9 / 2 # => 4 5 % 3 # => 2 -3.abs # => 3 1.class # => Fixnum (2**50).class # => Bignum 1.3.class # => Float
  33. 33. Arrays Array.new # => [] [1,2,3] # => [1, 2, 3] [1] + [2] << 3 # => [1, 2, 3] [1,2,3] - [2,3] # => [1] %w[one two] # => ["one", "two"] [1,2,3].pop # => 3 [1,2].push(3) # => [1, 2, 3] [1,2,3].shift # => 1 [2,3].unshift(1) # => [1, 2, 3] [1,3].insert(1,2) # => [1, 2, 3]
  34. 34. Hashes options = {:name => "Devnology"} h = Hash.new # => {} h['string'] = 1 h[:symbol] = 1 h # => {:symbol=>1, "string"=>1} h.keys # => [:symbol, "string"] h[:symbol] # => 1
  35. 35. Iterators for n in 0..2 puts n end (0..2).each do |n| puts n end [0,1,2].each {|n| puts n}
  36. 36. Enumerable ary = [1,2,3] ary.map {|n| n * 2} # => [2, 4, 6] ary.select {|n| n % 2 == 0} # => [2] ary.inject(0) {|sum, n| sum + n} # => 6
  37. 37. Control structures if some_condition # ... elsif other_condition # ... else # ... end while condition # ... end puts "lol" if funny?
  38. 38. Regular Expressions str = "Hello, world!" str.gsub(/[aeiou]/,"*") # => "H*ll*, w*rld!" str =~ /w(or)ld/ # => 7 $1 # => "or" match = str.match(/w(or)ld/) # => #<MatchData: 0x532cbc> match[0] # => "world" match[1] # => "or"
  39. 39. Error handling begin raise "Standard error" rescue => e p e end # >> #<RuntimeError: Standard error> begin raise StandardError.new("Oh, oh") rescue RuntimeError puts "runtime" rescue StandardError puts "standard" end # >> standard
  40. 40. System interaction system "ls" output = `ls` ARGV File.open('test.txt','w') do |file| file.write("linen") file.puts("line") end File.read('test.txt')
  41. 41. Classes class Calc attr_accessor :factor def initialize(factor=2) @factor = factor end def multiply(value) @factor * value end end calc = Calc.new calc.multiply 5 # => 10 calc.factor = 3 calc.multiply 5 # => 15
  42. 42. Inheritance class Foo def greet "Hi, #{value}" end def value "foo" end end class Bar < Foo def value "bar" end end Foo.new.greet # => "Hi, foo" Bar.new.greet # => "Hi, bar"
  43. 43. Mixins & Open Classes module Even def even? self % 2 == 0 end end class Fixnum include Even end 1.even? # => false 2.even? # => true
  44. 44. Class methods class Foo def self.bar "BAR!" end def bar "bar" end end Foo.bar # => "BAR!" Foo.new.bar # => "bar"
  45. 45. Basic tools of a Rubyist
  46. 46. Rubygems
  47. 47. Rdoc
  48. 48. Interactive Ruby
  49. 49. Practical uses of Ruby
  50. 50. Ruby on Rails class BlogPost < ActiveRecord::Base belongs_to :user has_many :comments validates_presence_of :user_id validates_associated :user validates_length_of :title, :within => 10..100 validates_length_of :body, :within => 100..5000 end BlogPost.new(:title => "Hello", :body => "foo!")
  51. 51. Rspec it "should be awesome" do foobar = FooBar.new foobar.should be_awesome end
  52. 52. Cucumber Feature: Write blog post As a blogger I want to create a new blog post So that I can share my knowledge Scenario: Click the Add group button Given I am on the homepage When I follow "New post" Then I should be on the new blog post page Given /^I am on (.+)$/ do |page_name| visit path_to(page_name) end
  53. 53. Scripting / automation
  54. 54. DSL: Rake desc "Clean everything up" task :cleanup do Cleaner.cleanup! end desc "Make sure everything is shiny" task :shiny => :cleanup do Shiner.polish! end
  55. 55. DSL: Capistrano set :application, "blog" set :repository, "git@github.com:Narnach/#{application}.git" set :deploy_to, "/var/www/www.#{application}.com" set :scm, :git role :web, "server" role :app, "server" role :db, "server", :primary => true namespace :deploy do desc "Restart Passenger" task :restart, :roles => :app, :except => { :no_release => true } do run "touch #{File.join(current_path,'tmp','restart.txt')}" end end
  56. 56. The Ruby Community
  57. 57. Rubyists
  58. 58. Amsterdam.rb Monthly beer night Presentation nights
  59. 59. Utrecht.rb Monthly beer night
  60. 60. rubyists.eu
  61. 61. ruby-groups.org dev-groups.org

Editor's Notes

  • Overview:
    * Top-level: what is it?
    * Low-level: how does it look?
    * Purpose: What can you use it for?
    * Practice: what is it used for?
  • Overview:
    * Top-level: what is it?
    * Low-level: how does it look?
    * Purpose: What can you use it for?
    * Practice: what is it used for?
  • * Simple strings
    * Puts -&gt; global scope
    * Interpolation
    * Methods, parameters
    * Single quotes vs double quotes
  • * Simple strings
    * Puts -&gt; global scope
    * Interpolation
    * Methods, parameters
    * Single quotes vs double quotes
  • ×