Ruby/Class/getter setter

# Ruby simplifies the creation of getters and setters with a little metaprogramming and the methods attr, attr_reader, attr_writer, and attr_accessor, all from the Module class. 
# By supplying the attr method, Ruby provides a way to quickly create the equivalent of six lines of code with a single line.
# The method attr creates a single getter method, named by a symbol, with an optional setter method (if the second argument is true)
 
#!/usr/bin/env ruby
class Dog
  attr :bark, true
end
Dog.instance_methods - Object.instance_methods # => ["bark", "bark="]
dog = Dog.new
dog.bark="Woof!"
puts dog.bark # => Woof!
 
# single line attr :bark, true is equivalent to writing out the bark and bark= methods in six lines of code:
class Dog
  def bark
    @bark
  end
  def bark=(val)
    @bark = val
  end
end

class Animal
  def initialize
    @color = "red"
  end
  def get_color
    return @color
  end
end

class Animal
  def initialize
    @color = "red"
  end
  def get_color
    return @color
  end
end
animal = Animal.new
puts "The new animal is " + animal.get_color

#!/usr/bin/env ruby
class Horse
  def initialize( name )
    @name = name
  end
  def horse_name
    @name
  end
end
horse = Horse.new( "Doc Bar" )
puts horse.horse_name # => Doc Bar

# The setter method name= follows a Ruby convention: the name of the method ends with an equals sign (=). 
 
class Horse
  def name
    @name
  end
  def name=( value )
    @name = value
  end
end
h = Horse.new
h.name= "Poco Bueno"
h.name # => "Poco Bueno"

#!/usr/bin/env ruby
class Dog
  attr_reader :bark
  attr_writer :bark
end
dog = Dog.new
dog.bark="Woof!"
puts dog.bark # => Woof!
p dog.instance_variables.sort # => ["@bark"]
p Dog.instance_methods.sort - Object.instance_methods # => [ "bark", "bark=" ]

class CD
  include Comparable
  @@plays = 0
  attr_reader :name, :artist, :duration
  attr_writer :duration
  def initialize(name, artist, duration)
    @name     = name
    @artist   = artist
    @duration = duration
    @plays    = 0
  end
  def to_s
    "CD: #@name--#@artist (#@duration)"
  end
  def name
    @name
  end
  def artist
    @artist
  end
  def duration
    @duration
  end
end
d = CD.new("B", "F", 260)
d.artist
d.name
d.duration

class Song
  include Comparable
  @@plays = 0
  attr_reader :name, :artist, :duration
  attr_writer :duration
  def initialize(name, artist, duration)
    @name     = name
    @artist   = artist
    @duration = duration
    @plays    = 0
  end
  def to_s
    "Song: #@name--#@artist (#@duration)"
  end
  def duration=(new_duration)
    @duration = new_duration
  end
  def inspect
    self.to_s
  end
end
song = Song.new("Bicylops", "Fleck", 260)
song.duration
song.duration = 257   # set attribute with updated value
song.duration

class CD
  include Comparable
  @@plays = 0
  attr_reader :name, :artist, :duration
  attr_writer :duration
  def initialize(name, artist, duration)
    @name     = name
    @artist   = artist
    @duration = duration
    @plays    = 0
  end
  def to_s
    "CD: #@name--#@artist (#@duration)"
  end
  def duration_in_minutes=(new_duration)
    @duration = (new_duration*60).to_i
  end
  def play
    @plays  += 1   # same as @plays = @plays + 1
    @@plays += 1
    "This  CD: #@plays plays. Total #@@plays plays."
  end
  def record
    "Recording..."
  end
  def inspect
    self.to_s
  end
  def <=>(other)
    self.duration <=> other.duration
  end
end