ruby-on-rails – rails simple_nested_form_for fields_for错误

<%= simple_nested_form_for(@person,:url => collection_url,:html=>{:multipart => true}) do |f| %>
  <%= render :partial => "form",:locals => { :f => f } %>
<% end %>

但部分中的这一行导致了问题：

<h2>Badges</h2> 
<ul id="certifications">
// this following line is raising the error "wrong number of arguments (4 for 3)"
<%= f.fields_for :certifications do |certification_form| %> 
    <%= render :partial => 'certification',:locals => { :f => certification_form } %>
<% end %>
</ul>
<%= f.link_to_add "Add a Badge",:certifications %>

所以这是模型：

class Person < ActiveRecord::Base
  has_many :certifications,:dependent=>:destroy,:order=>:position
  has_many :certificates,:through=>:certifications
  accepts_nested_attributes_for :certifications,:allow_destroy => true
end

控制器正在使用继承的资源gem.

怎么了？谢谢您的帮助.