我正在尝试构建用于添加议程的复杂表单，并且我想使用link_to_add helper动态地为表单中的给定议程添加新用户。使用nested_form宝石和accepts_nested_attributes_for方法。这些是我的模型：
class Agenda < ActiveRecord::Base
has_many :roles
has_many :users, through: :roles
accepts_nested_attributes_for :roles
belongs_to :owner, class_name: User
attr_accessible :name,
:address,
:owner,
:roles_attributes
end
class Role < ActiveRecord::Base
belongs_to :agenda
belongs_to :user
accepts_nested_attributes_for :user
attr_accessible :agenda,
:role,
:user
end
class User < ActiveRecord::Base
has_many :roles
has_many :agendas, through: :roles
end
和我的控制器：
class AgendasController < ApplicationController
...
def new
@agenda = Agenda.new
@role = @agenda.roles.build
@user = @role.build_user
end
end
和我的表格：
<%= nested_form_for @agenda do |f| %>
....
<%= f.fields_for :roles do |role_f| %>
<%= role_f.fields_for :user do |user_f| %>
<div class="control-group">
<%= user_f.label :email, :class=>"control-label" %>
<div class="controls controls-row">
<%= user_f.text_field :email %>
</div>
</div>
<% end %>
<div class="control-group">
<%= role_f.label :role, :class=>"control-label" %>
<div class="controls controls-row">
<%= role_f.text_field :role %>
</div>
</div>
<%= role_f.link_to_remove "Remove user" %>
<% end %>
<%= f.link_to_add "Add new users", :roles %>
<% end %>
一切正常，除了不附加fields_for :user块的link_to_add。如何使 link_to_add 助手与fields_for :roles块一起渲染整个fields_for :user块？