title: Rails 3. How to add a helper that ActiveAdmin will use?
body: <p>I'm creating a helper to be used by Formtastic but I get the <code>undefined local variable or method</code> error. I don't know where to put it so it can work.</p>
  
  <p>I already tried in the application_helper.rb and in app/helpers/active_admin/view_helpers.rb</p>