title: Passing id in form_for action
body: <p>I have a form to update an attribute of a model - I don't want it to go to the standard update action I want it to go to a different action.</p>
  
  <pre><code>&lt;% for car in @cars %&gt;
   &lt;%= form_for car, :url =&gt; { :action =&gt; "custom_action/#{car.id}" } do |f| -%&gt;
  </code></pre>
  
  <p>This is giving the following error - </p>
  
  <pre><code>No route matches {:action=&gt;"custom_action/1", :controller=&gt;"cars"}
  </code></pre>
  
  <p>However if I visit the url - custom_action/1 - I don't get the routing error.</p>
  
  <p>Any idea why I can't do this?</p>