no_grandchildren.rb

class A
  def self.inherited inheriter
    class << inheriter
      def inherited inheriter
         Object.const_set inheriter.name.to_sym, self
         p "Sorry, A can't have grandchildren. You, #{inheriter}, are instead to be of class #{self}."
      end
    end
  end
end


class B < A
  def looks_into_the_mirror
    p "OMG! I have become my parents!"
  end
end


class C < B
  def looks_into_the_mirror
    p "Ah, it was just a nightmare."
  end
end


c = C.new


c.looks_into_the_mirror