Design/Architecture: Monitor and save attribute change
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I'm using the [merit][1] gem to give points to users on various controller actions. Now I'm searching for a way to store points gained for certain classes of users in their cookie. 

What I'd like to do is monitor the changes made to `User.points` during a request in a non-invasive way. Until now I as far as subscribing to a `ActiveSupport::notification` without touching the `User` class, and monitoring the changes there. The harder part is: how to store the data? Since in the notification there is no access to the `request`, `current_user` or `cookies`. A possible implementation would be to store the variables in a cache and write it in a after filter. Can you recommend a better approach?


  [1]: https://github.com/tute/merit