How to get at the underlying object inside a Rails form or field_for block?

Question

I can't figure-out how to get at the underlying object in a form_for or field_for block.

What I'd like to do is something like:

<% f.fields_for :children do |child_form| %>
  <%= render :partial => "#{child_form.underlying_object.class.name.downcase}" %>
<% end %>

and :children is a polymorphic has_many association.

Suggestions?

Answer 1

Isn't it just

<% f.fields_for :children do |child_form| %>
<%= render :partial => "#{child_form.object.name.downcase}" %>
<% end %>