rails 3 form_for doesn't output anything

Hi I have any form with nested form, for example

<% form_for :main do |f| %>
  trying to insert code here
 开发者_如何学Python <% fields_for :nested do |nested_form| %>
    <%= nested_form.text_field :description %>
  <% end %>
<% end %>

And then I am trying to insert anything to a main form, nested form doesn't produce any output. It outputs only when it is the only object in main form. Any suggestions?

---

From the Rails 3 documentation examples you need to write your form_for like this:

<%= form_for :main do |f| %>
  # trying to insert code here
   <%= fields_for :nested do |nested_form| %>
    <%= nested_form.text_field :description %>
  <% end %>
<% end %>

Note the <%= for both form_for and fields_for