Modules for macros. In reference to: http://thepugautomatic.com/2013/07/dsom/

macro_modules.rb

class SomeORM
  def self.attributes(*names)
    if const_defined?(:DynamicAttributes, false)
      mod = const_get(:DynamicAttributes)
    else
      mod = const_set(:DynamicAttributes, Module.new)
      include mod      
    end
    mod.module_eval do
      names.each do |name|
        define_method(name) do
          # Stuff
        end
      end
    end
  end
end

Thanks for the feedback!

I like how this solution uses plain constants to keep down the number of modules (one per class in an inheritance hierarchy), unique-enough names (no need for object ids as it's again one per class), and of course for naming.

One thing I dislike slightly about this compared to my original solution is that Post::DynamicAttributes perhaps gives less of a clue where the module comes from than SomeORM::DynamicAttributes123. But I suppose "where it comes from" is kind of hard to decide anyway – SomeORM generates it, but you declared the attributes in Post, which is-a SomeORM anyway.

I suppose you could call it Post::SomeORMDynamicAttributes if you want to be very clear.

I also like to define a custom #to_s on these modules so that when listed with #ancestors you see e.g. DynamicAttributes(attr1, attr2, attr3). I think I showed that in one of the RubyTapas episodes I mentioned on Twitter.

I checked out episode 28, it's in there. Clever!

For my own future reference, the above could be achieved with something along the lines of (after line 15):

def mod.to_s
  "DynamicAttributes(#{instance_methods(false).join(', ')})"
end