问Rails 3.1: accepts_nested_attributes_for和has_one联合-不起作用吗？

EN

class User < ActiveRecord::Base
  # current location
  has_one :location, :dependent => :destroy
  accepts_nested_attributes_for :location
end

class Location < ActiveRecord::Base
  belongs_to :user
end

<%= form_for(@user) do |f| %>  
    <%= fields_for(@user.location) do |location_fields| %>
        <%= location_fields.label :current_location_text, 'Current Location' %>
        <%= location_fields.text_field :current_location_text, :placeholder => 'Road, City or Postcode' %>
    <% end %>

    <%= f.submit "Update Current Location" %>
<% end %>

Started PUT "/users/1" for 127.0.0.1 at 2011-10-08 00:28:05 +0100
  Processing by UsersController#update as HTML
  Parameters: {"utf8"=>"✓", "authenticity_token"=>"YdTAsXwEvRgXIqri+jfx3dLlYG2XWQTuYkgLDsO/OJw=", "location"=>{"current_location_text"=>"E14 8JS"}, "commit"=>"Update Current Location", "id"=>"1"}
  User Load (10.3ms)  SELECT `users`.* FROM `users` WHERE `users`.`id` = 1 LIMIT 1
  User Load (5.3ms)  SELECT `users`.* FROM `users` WHERE `users`.`id` = ? LIMIT 1  [["id", "1"]]
  SQL (4.4ms)  BEGIN
   (2.5ms)  COMMIT
Redirected to http://localhost:3000/users/1

if @user.update_attributes(params[:user])
  redirect_to current_user, :notice => 'User was successfully updated.'
else
  render :action => "edit"
end

resources :users do
  resource :location
end