gistfile1.rb

class Dog
  @@all_dogs = []
  
  def initialize(name)
    @@all_dogs << self
    @name = name
  end
  
  def self.bark
    @@all_dogs.each {|dog| dog.bark }
  end
  
  def bark
    puts "#{@name}: Bark!"
  end
end

harleigh = Dog.new('har har')
mala = Dog.new('mala')

mala.bark # mala: Bark!
harleigh.bark # har har: Bark!

Dog.bark # mala: Bark!, har har: Bark!