Final round of animals

animals_final.rb

class Animal
  @animals = []
  LEGS = 4
  
  class << self
    attr_reader :animals
    alias :all :animals
  end
 
  def initialize(args={})
    Animal.animals << self
    after_initialize(args)
  end
 
  def after_initialize(args)
  end
 
  def legs
    self.class::LEGS
  end
end
 
 
class Octopus < Animal
  @animals = []
  LEGS = 8
 
  def after_initialize(args={})
    self.class.animals << self
  end
end
 
 
class Llama < Animal
  @animals = []
 
  def after_initialize(args={})
    self.class.animals << self
  end
end

Octopus.new.legs # => 8
Llama.new.legs # => 4
Animal.all # => [#<Octopus:0x000001010ef220>,#<Llama:0x000001010a6868>]
Octopus.all # => [#<Octopus:0x000001010ef220>]
Llama.all # => [#<Llama:0x000001010a6868>]