gistfile1.txt

<%= form_for(@opportunity) do |f| %>
#...
      <% f.fields_for :opportunity_filters do |filter_form| %>
        <%= render 'opportunity_filters/edit_form', 
          :collection => @opportunity.opportunity_filters, 
          :as => :opportunity_filter, :locals => {:f => filter_form} %>
      <% end %>
#..
<% end %>