title: Create one interface for many models?
body: <p>I'm currently working on a custom shop software written in Ruby on Rails with three gift/voucher models. One is for percentage discount, one for a specific amount and one is for groups. Now it needs to be overhauled and I was thinking to create an interface, model with polymorphic relations to the old models or something similiar to add features and functionalities to all three models.</p>
  
  <p>How would you approach is? I think I'd go for model with polymorphic relations. Any suggestions weclome!</p>