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copied!<p>STI is probably a good fit for your requirements, as suggested by tadman, if you are using ActiveRecord (from Rails 3, it is easy to change ORM). The basic information is available on the <a href="http://ar.rubyonrails.org/classes/ActiveRecord/Base.html" rel="nofollow noreferrer">AR documentation page</a>, but here is some extra information w.r.t. your target:</p> <ul> <li>Define one model per file. Otherwise there are some initialization troubles. Assuming Client inherits from User all in a single file, Client objects cannot be created as long as a User constructor has not been called once. One file per model circumvents the problem.</li> <li>All attributes through the hierarchy are defined one-shot in the top class. This is for performance issues, but it seems disturbing many people in blog posts. In short, the Ruby code is object-oriented and encapsulates properly the attributes. The DB contains everything in a single table, with the extra "type" column to distinguish where they belong in the hierarchy. This is only a "trick" to represent inheritance trees in relational databases. We must be aware that the ORM mapping is not straightforward. The <a href="http://www.martinfowler.com/eaaCatalog/singleTableInheritance.html" rel="nofollow noreferrer">image on this site from Martin Fowler</a> may help understand the situation.</li> </ul> <p>In addition, you would like any new user to be a client, where Client inherits from User. To do so, you may simply instantiate any new user as a client. In your controller for creating users:</p> <pre><code>user = Client.new # Do something to user user.save #=> <Client id: 1, name: "Michael Bolton", email: "mike@bolton.net", created_at: "2010-05-30 03:27:39", updated_at: "2010-05-30 03:27:39"> </code></pre> <p>All the above is still valid with Rails 3 when using ActiveRecords.</p>

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