Here's that stuff about Factory methods in Ruby

gistfile1.rb

class Mammal

  def self.factory(type)
		if choice == "Dog"
			mammal = Dog.new
		elsif choice == "Cat"
			mammal = Cat.new
		elsif choice == "Whale"
			mammal = Whale.new
		else
			puts "Sorry don't know what that is..."
		end
	end
end

class Dog < Mammal
end

class Cat < Mammal
end

class Whale < Mammal
end

mammal = nil
puts "What sort of mammal would you like?"
choice = gets.strip.chomp
mammal = Mammal.factory(choice)