title: How can a single form_for work for new, update and edit?
body: <p>In rails 3, is it possible to create a form_for that works for both new, update and edit actions?</p>
  
  <p>If yes, how do I do this?</p>
  
  <p>I have a admin section so my urls look like:</p>
  
  <pre><code>/admin/posts/ {new,update, edit}
  </code></pre>