Ruby: How do I refactor code from two module class methods?

Question

Here's the code:

module A
  class C1
    def self.grovel(x)
      return A::helper(x) + 3
    end
  end

  class C2
    def self.grovel(x)
      return A::helper(x) + 12
    end
  end
  private
  def helper(y)
    y + 7
  end
  module_function :helper
end

f = A::C1.grovel(7)
puts f
puts A::C2.grovel(25)

I'm working with legacy code, trying to avoid changing too much. I'm not sure I would have made two separate classes with the same method, as each class only contains one method, with common code. I want to extract the common code into a method that only the methods in A can see, but still have to invoke it with its fully qualified name ("A::helper").

Is there a better way of doing this? Ideally, I'd like to wrap the common code in a method (let's still call it "helper") that can be invoked from within the class grovel methods without any qualification, but isn't easily available to code outside module A.

Thanks.

Answer 1

Minixs are useful, when the proper inheritance can't be applied, for example, then a class must be inherit properties of the two other classes, therefore you can just use the inheritance mechanics here:

module A
  class C
    def self.helper(y)
      y + 7
    end
  end

  class C1 < C
    def self.grovel(x)
      return self.helper(x) + 3
    end
  end

  class C2 < C
    def self.grovel(x)
      return self.helper(x) + 12
    end
  end
end

puts A::C1.grovel(7)
puts A::C2.grovel(25)

Answer 2

How about creating another module?

module A
  module Helper
    def helper(y)
      y + 7
    end
  end  

  class C1
    class << self
      include A::Helper    

      def grovel(x)
        return helper(x) + 3
      end
    end
  end

  class C2
    class << self
      include A::Helper    

      def grovel(x)
        return helper(x) + 12
      end
    end
  end


end

puts A::C1.grovel(7)
puts A::C2.grovel(25)

You create a submodule of A, and include it in your classes as a Mixin. That way only these classes can access the method.

You can see it working in http://rubyfiddle.com/riddles/31313