A class that make an attribute unique.

a.rb

class A
   attr_accessor :name
   @@a_classes = []
   private_class_method :new

   def A.find_or_create(name)
    @@a_classes.each do |klass|
      if klass.name == name
        return klass
      end
    end
    new_klass = new name
    @@a_classes.push(new_klass)
    new_klass
   end

   def initialize(name)
    self.name = name
   end
end