I'm defining my own AR class in Rails that will include dynamically created instance methods for user fields 0-9. The user fields are not stored in the db directly, they'll be serialized together since they'll be used infrequently. Is the following the best way to do this? Alternatives?

Where should the start up code for adding the methods be called from?

class Info < ActiveRecord::Base

end

# called from an init file to add the instance methods
parts = []
(0..9).each do |i|
   parts.push "def user_field_#{i}"     # def user_field_0
   parts.push   "get_user_fields && @user_fields[#{i}]"
   parts.push "end"
end

Info.class_eval parts.join