## The setup
*bonus has_one photo, photo belongs_to bonus
*i've confirmed @bonus is not nil at this point
## The question
why does it say 'nil_class' instead of 'bonus' or 'photo' or something nice?
## The View
<% form_for(@bonus, :html => { :multipart => true }) do |f| %>
  <% fields_for @bonus.photo do |photo_field| %>
    image file: <%= photo_field.file_field :uploaded_data %>
  <% end %>
...other regular bonus fields...
  <%= f.submit "Update" %>
<% end %>
## The Resulting HTML
 <h2>Upload a new photo</h2>
    image file: <input id="nil_class_uploaded_data" name="nil_class[uploaded_data]" size="30" type="file" />
## The clean pastie knowledge-gain acknowledgment
um, thanks leeth, yer the shit