title: Rails AJAX: My partial needs a FormBuilder instance
body: <p>So I've got a form in my Rails app which uses a custom FormBuilder to give me some custom field tags</p>
  
  <pre><code>&lt;% form_for :staff_member, @staff_member, :builder =&gt; MyFormBuilder do |f| %&gt;
  [...]
      &lt;%= render :partial =&gt; "staff_members/forms/personal_details", :locals =&gt; {:f =&gt; f, :skill_groups =&gt; @skill_groups, :staff_member =&gt; @staff_member} %&gt;  
  [...]
  &lt;% end %&gt;
  </code></pre>
  
  <p>Now, this partial is in an area of the form which gets replaces by an AJAX callback. What I end up doing from the controller in response to the AJAX request is:</p>
  
  <pre><code>render :partial =&gt; "staff_members/forms/personal_details", :locals =&gt; {:skill_groups =&gt; @skill_groups, :staff_member =&gt; @staff_member}
  </code></pre>
  
  <p>However, if I do that then the form breaks, as the FormBuilder object I used in the form_for is no longer available. Is there any way for me to use my custom FormBuilder object inside a partial used for an AJAX callback?</p>