Getting Started with Ruby

Some quick tips to getting started with Ruby. Presented at Motorola Solutions' APPFORUM Americas 2012 in Schaumburg, IL.

Transcript

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2. RUBY
   Getting Started
   DANIEL MORRISON Ι COLLECTIVE IDEA
   APPFORUM Americas 2012
   

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3. WELCOME
   Daniel Morrison
   • @danielmorrison
   • Founder, Collective Idea
   • Based in Holland, Michigan
   • Programmer
   • Ruby & Rails Instructor
   

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4. RUBY
   Language
   • Dynamic
   • Object-Oriented
   • Designed for Programmer Productivity
   Ruby on Rails
   • Web Framework
   • Launched Ruby into the public eye
   • Inspiration for many other frameworks
   RhoMobile
   • Uses Ruby to bridge devices
   • Rhodes framework takes cues from Rails
   

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5. CORE
   RUBY
   

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6. DATA TYPES
   Numbers
   • Integer types:
   • 5.class #=> Fixnum
   • 9999999999999999999.class # => Bignum
   

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7. DATA TYPES
   Numbers
   • Integer types:
   • 5.class #=> Fixnum
   • 9999999999999999999.class # => Bignum
   Arithmetic Operation
   • + add
   • - subtract
   • * multiply
   • / divide
   • % modulus
   • ** exponent
   

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8. STRINGS
   Strings in ruby
   • “Hello World”
   • Can use single or double quoted.
   • As well as more esoteric syntaxes: %q|Hello World|
   

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9. STRINGS
   Strings in ruby
   • “Hello World”
   • Can use single or double quoted.
   • As well as more esoteric syntaxes: %q|Hello World|
   String Interpolation
   • “There are #{24 * 7} hours in a week.”
   • Only works with double quotes.
   

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10. METHODS
    

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11. METHODS
    Methods in ruby
    • Called Functions in other languages
    Define and call
    • def my_addition(value1, value2)
    value1 + value2
    end
    • my_add(10, 5) # => 15
    

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12. VARIABLES
    

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13. VARIABLES
    Define a variable
    • a = “Hello World”
    • No need to specify type
    • Can redefine at any time
    • a = 15
    

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14. VARIABLES
    Define a variable
    • a = “Hello World”
    • No need to specify type
    • Can redefine at any time
    • a = 15
    Strong Dynamic Typing
    • Strong: variable always has an explicit type
    • Dynamic: type can change at any time
    

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15. VARIABLES
    Define a variable
    • a = “Hello World”
    • No need to specify type
    • Can redefine at any time
    • a = 15
    Strong Dynamic Typing
    • Strong: variable always has an explicit type
    • Dynamic: type can change at any time
    Duck Typing
    • def my_addition(value1, value2)
    value1 + value2
    end
    • my_addition(“Hello”, “World”) # => “HelloWorld”
    

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16. COLLECTION
    DATA TYPES
    

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17. ARRAY
    Easy to create
    • a = [5, 10, 45, 9]
    • a = Array.new(5, 10, 45, 9) # works, but not usually used.
    

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18. ARRAY
    Easy to create
    • a = [5, 10, 45, 9]
    • a = Array.new(5, 10, 45, 9) # works, but not usually used.
    Easy to access & modify
    • a[2] # => 45
    • a[0] = 1000 # => [1000, 10, 45, 9]
    

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19. ARRAY
    Easy to create
    • a = [5, 10, 45, 9]
    • a = Array.new(5, 10, 45, 9) # works, but not usually used.
    Easy to access & modify
    • a[2] # => 45
    • a[0] = 1000 # => [1000, 10, 45, 9]
    Polyglot
    • b = [“banana”, 3.14, -200, “Hello World”]
    • Mix & match values
    

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20. ARRAY
    Easy to create
    • a = [5, 10, 45, 9]
    • a = Array.new(5, 10, 45, 9) # works, but not usually used.
    Easy to access & modify
    • a[2] # => 45
    • a[0] = 1000 # => [1000, 10, 45, 9]
    Polyglot
    • b = [“banana”, 3.14, -200, “Hello World”]
    • Mix & match values
    Dynamically Sized
    • fruits = [“Apple”, “Banana”]
    • fruits[2] = “Orange” # => [“Apple”, “Banana”, “Orange]
    • fruits.length # => 3
    

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21. HASH
    Key-Value Store
    • AKA: HashTable, Dictionary, associative array
    • Key is unique
    

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22. HASH
    Key-Value Store
    • AKA: HashTable, Dictionary, associative array
    • Key is unique
    Easy to Create
    • h = {“name” => “Daniel”, “language” => “Ruby”}
    

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23. HASH
    Key-Value Store
    • AKA: HashTable, Dictionary, associative array
    • Key is unique
    Easy to Create
    • h = {“name” => “Daniel”, “language” => “Ruby”}
    Easy to Access
    • Array-like syntax
    • h[“name”] # => “Daniel”
    • h[“age”] # => nil
    • h[“age”] = 10 # => {“name” => “Daniel”, “age => 10, “language” => “Ruby”}
    

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24. HASH
    Key-Value Store
    • AKA: HashTable, Dictionary, associative array
    • Key is unique
    Easy to Create
    • h = {“name” => “Daniel”, “language” => “Ruby”}
    Easy to Access
    • Array-like syntax
    • h[“name”] # => “Daniel”
    • h[“age”] # => nil
    • h[“age”] = 10 # => {“name” => “Daniel”, “age => 10, “language” => “Ruby”}
    Symbols
    • Begin with a colon
    • Most often used as hash keys
    • h = {:name => “Alice”, :age => 10}
    • h[:age] # => 10
    • h[“age”] # => nil
    

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25. NESTING
    Both Hash & Array can contain each other
    • apple = {“name” => “Apple”, “colors” => [“red”, “green”]}
    • banana = {“name” => “Banana”, “colors” => [“yellow”]}
    • fruits = [apple, banana]
    • fruits.last # => {“name” => “Banana”, “colors” => [“yellow”]}
    

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26. NESTING
    Both Hash & Array can contain each other
    • apple = {“name” => “Apple”, “colors” => [“red”, “green”]}
    • banana = {“name” => “Banana”, “colors” => [“yellow”]}
    • fruits = [apple, banana]
    • fruits.last # => {“name” => “Banana”, “colors” => [“yellow”]}
    Multidimensional Arrays
    • matrix = [[3, 2, 6], [1, 4, 5], [7, 4, 7]]
    • matrix[0] # => [3, 2, 6]
    

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27. RANGE
    Ranges of values
    • r = (10..100)
    • r.include?(20) # => true
    • r.include?(2) # => false
    

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28. RANGE
    Ranges of values
    • r = (10..100)
    • r.include?(20) # => true
    • r.include?(2) # => false
    Useful with Dates & Times
    • jan1 = Date.new(2012, 1, 1)
    • dec31 = Date.new(2012, 1, 1)
    • (jan1..dec31).include?(Date.today) # => true
    • (jan1..dec31).include?(Date.today + 365) # => false
    

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29. REGULAR
    EXPRESSIONS
    

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30. REGULAR EXPRESSIONS
    Easy to Create
    • r = Regexp.new(“\d\d\d\d-\d\d-\d\d”)
    • r = /\d\d\d\d-\d\d-\d\d/
    

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31. REGULAR EXPRESSIONS
    Easy to Create
    • r = Regexp.new(“\d\d\d\d-\d\d-\d\d”)
    • r = /\d\d\d\d-\d\d-\d\d/
    Match Strings
    • info = “Conference runs from 2012-06-04 to 2012-06-06”
    • Use =~ to find match location
    • info =~ /\d\d\d\d-\d\d-\d\d/ # => 21
    • Use match to get the data back
    • info.match(/\d\d\d\d-\d\d-\d\d/) # => #
    

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32. REGULAR EXPRESSIONS
    Easy to Create
    • r = Regexp.new(“\d\d\d\d-\d\d-\d\d”)
    • r = /\d\d\d\d-\d\d-\d\d/
    Match Strings
    • info = “Conference runs from 2012-06-04 to 2012-06-06”
    • Use =~ to find match location
    • info =~ /\d\d\d\d-\d\d-\d\d/ # => 21
    • Use match to get the data back
    • info.match(/\d\d\d\d-\d\d-\d\d/) # => #
    Substitutions
    • info.sub(/\d\d\d\d-\d\d-\d\d/, “today”)
    - #=> “Conference runs from today to 2012-06-06”
    • info.gsub(/\d\d\d\d-\d\d-\d\d/, “today”)
    - #=> “Conference runs from today to today”
    

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33. REGULAR EXPRESSIONS
    Test with rubular.com
    

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34. CONDITIONALS
    AND LOOPS
    

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35. IF STATEMENTS
    if
    • if input == “quit”
    exit
    end
    

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36. IF STATEMENTS
    if
    • if input == “quit”
    exit
    end
    Single line if
    • exit if input == “quit”
    

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37. IF STATEMENTS
    if
    • if input == “quit”
    exit
    end
    Single line if
    • exit if input == “quit”
    unless
    • unless input == “quit”
    do_work
    end
    • do_work unless input == “quit”
    

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38. ELSE
    Test multiple conditions
    • if input == “quit”
    exit
    elsif input == “pause”
    sleep 20
    else
    do_work
    end
    

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39. ELSE
    Test multiple conditions
    • if input == “quit”
    exit
    elsif input == “pause”
    sleep 20
    else
    do_work
    end
    • Note the spelling of elsif
    

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40. CASE
    Ruby’s powerful case statement
    • case input
    when “quit”
    exit
    when “pause”
    sleep 20
    when String
    puts “The input is #{input}”
    when 5..10
    puts “The input was between 5 and 10”
    when /\d\d\d\d-\d\d-\d\d/
    puts “The input looks like a date”
    else
    puts “I don’t understand you.”
    end
    

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41. WHILE
    Simple while loop
    • count = 0
    • while count < 10
    • puts count
    • count += 1
    • end
    

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42. WHILE
    Simple while loop
    • count = 0
    • while count < 10
    • puts count
    • count += 1
    • end
    +=
    • Equivalent to count = count + 1
    • Can be used with any number
    • And all basic math operations (*=, -=, etc.)
    

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43. WHILE
    Simple while loop
    • count = 0
    • while count < 10
    • puts count
    • count += 1
    • end
    +=
    • Equivalent to count = count + 1
    • Can be used with any number
    • And all basic math operations (*=, -=, etc.)
    Inline while
    • count = 0
    • puts count += 1 while count < 10
    

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44. UNLESS
    Unless is the inverted while
    • count = 0
    • unless count >= 10
    • puts count
    • count += 1
    • end
    

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45. UNTIL
    until is the inverted while
    • count = 0
    • until count >= 10
    • puts count
    • count += 1
    • end
    Inline until
    • count = 0
    • puts count += 1 until count >= 10
    

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46. FOR
    For exists in Ruby
    • for fruit in fruits
    • puts “I love #{fruit}
    • end
    

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47. FOR
    For exists in Ruby
    • for fruit in fruits
    • puts “I love #{fruit}
    • end
    But we don’t use it.
    

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48. ITERATION
    THE RUBY WAY
    

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49. EACH
    Use each for iterating
    • fruits.each do |fruit|
    • puts “I love #{fruit}”
    • end
    

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50. EACH
    Use each for iterating
    • fruits.each do |fruit|
    • puts “I love #{fruit}”
    • end
    Use do & end for multi-line, {} for single-line
    • fruits.each {|fruit| puts “I love #{fruit}” }
    

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51. EACH
    Use each for iterating
    • fruits.each do |fruit|
    • puts “I love #{fruit}”
    • end
    Use do & end for multi-line, {} for single-line
    • fruits.each {|fruit| puts “I love #{fruit}” }
    Same syntax works for other forms of iterating
    • .map
    • .each_with_index
    • .each_key
    

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52. OBJECTS
    

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53. OBJECTS
    Objects
    • class Person
    end
    

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54. OBJECTS
    Objects
    • class Person
    end
    Inheritance
    • class Programmer < Person
    end
    

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55. OBJECTS
    Objects
    • class Person
    end
    Inheritance
    • class Programmer < Person
    end
    Constructors
    • class Person
    def initialize(name)
    @name = name
    end
    end
    

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56. RUBY ON RAILS
    

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57. RUBY ON RAILS
    What is Rails
    • Web Framework
    • Convention over Configuration
    • Geared toward database-backed
    web applications
    • Great for producing APIS
    

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58. EXAMPLE RAILS APP
    Demo time!
    • rails new demo
    • cd demo
    • rails generate scaffold person name:string age:integer
    • rails server
    

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59. USING
    JSON
    

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60. PARSING JSON
    In Rails
    • JSON.parse(json)
    Rhodes
    • Rho::JSON.parse(json)
    

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61. PARSING JSON
    In Rails
    • JSON.parse(json)
    Rhodes
    • Rho::JSON.parse(json)
    Both turn JSON into a Hash
    • {
    "name": "Bob",
    "age": 20,
    "friends": ["Alice", "Carol", "Dave"]
    }
    • {
    "name" => "Bob",
    "age" => 20,
    "friends" => ["Alice", "Carol", "Dave"]
    }
    

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62. XML IN RUBY
    XML is as easy as JSON
    • REXML::Document.new(xml_file)
    

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63. IRB
    INTERACTIVE RUBY
    

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64. IRB
    Command-line Ruby
    • irb
    • rails console
    

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65. IRB
    Command-line Ruby
    • irb
    • rails console
    Inspect data
    • puts x
    • x.inspect
    

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66. DEBUGGING
    Ruby Debugger
    • debugger gem, or ruby-debug
    • Both work similar to gdb
    

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67. DEBUGGING
    Read the Errors
    • They tell you line numbers
    NameError: undefined local variable or method `my_method' for #0x007fef2bc51ee0>
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/
    activerecord-3.2.2/lib/active_record/dynamic_matchers.rb:50:in
    `method_missing'
    from /Users/daniel/Projects/my_project/app/models/sign.rb:16:in `import'
    from (irb):4
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@project/gems/railties-3.2.2/lib/
    rails/commands/console.rb:47:in `start'
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/
    rails/commands/console.rb:8:in `start'
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/
    rails/commands.rb:41:in `'
    from script/rails:6:in `require'
    from script/rails:6:in `'
    

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68. DEBUGGING
    Read the Errors
    • They tell you line numbers
    NameError: undefined local variable or method `my_method' for #0x007fef2bc51ee0>
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/
    activerecord-3.2.2/lib/active_record/dynamic_matchers.rb:50:in
    `method_missing'
    from /Users/daniel/Projects/my_project/app/models/sign.rb:16:in `import'
    from (irb):4
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@project/gems/railties-3.2.2/lib/
    rails/commands/console.rb:47:in `start'
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/
    rails/commands/console.rb:8:in `start'
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/
    rails/commands.rb:41:in `'
    from script/rails:6:in `require'
    from script/rails:6:in `'
    

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69. DEBUGGING
    Read the Errors
    • They tell you line numbers
    NameError: undefined local variable or method `my_method' for #0x007fef2bc51ee0>
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/
    activerecord-3.2.2/lib/active_record/dynamic_matchers.rb:50:in
    `method_missing'
    from /Users/daniel/Projects/my_project/app/models/sign.rb:16:in `import'
    from (irb):4
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@project/gems/railties-3.2.2/lib/
    rails/commands/console.rb:47:in `start'
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/
    rails/commands/console.rb:8:in `start'
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@ project/gems/railties-3.2.2/lib/
    rails/commands.rb:41:in `'
    from script/rails:6:in `require'
    from script/rails:6:in `'
    

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70. DEBUGGING
    Read the Errors
    • They sometimes confuse you
    

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71. DEBUGGING
    Read the Errors
    • They sometimes confuse you
    @user.first_name
    

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72. DEBUGGING
    Read the Errors
    • They sometimes confuse you
    @user.first_name
    NoMethodError: undefined method `first_name' for nil:NilClass
    from (irb):1
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/
    lib/rails/commands/console.rb:47:in `start'
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/
    lib/rails/commands/console.rb:8:in `start'
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/
    lib/rails/commands.rb:41:in `'
    from script/rails:6:in `require'
    from script/rails:6:in `'
    

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73. DEBUGGING
    Read the Errors
    • They sometimes confuse you
    @user.first_name
    NoMethodError: undefined method `first_name' for nil:NilClass
    from (irb):1
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/
    lib/rails/commands/console.rb:47:in `start'
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/
    lib/rails/commands/console.rb:8:in `start'
    from /Users/daniel/.rvm/gems/ruby-1.9.3-p194@signwars/gems/railties-3.2.2/
    lib/rails/commands.rb:41:in `'
    from script/rails:6:in `require'
    from script/rails:6:in `'
    

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74. LEARN MORE
    

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75. LEARN MORE
    Documentation
    • http://ruby-doc.org
    • http://api.rubyonrails.org
    TryRuby
    • http://tryruby.org
    This Presentation
    • https://speakerdeck.com/u/danielmorrison
    • or shorter URL: http://bit.ly/LqCinu
    Talk to Me
    • @danielmorrison
    • http://collectiveidea.com
    

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