title: Send an extra parameter through a form in rails 3
body: <p>Is there a way to send an extra parameter through a form in rails 3?</p>
  
  <p>For example:</p>
  
  <pre><code>&lt;%= form_for @post do |f| %&gt;
  &lt;%= f.hidden_field :extraparam, :value =&gt; "22" %&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>but lets say :extraparam isn't part of the post model..</p>
  
  <p>I have an unknown attribute error in the create method of the controller when I try this, any ideas?</p>
  
  <p>(I want to use the param value itself in the controller for some extra logic)</p>