Ruby on rails 嵌套形式的质量赋值

我正在关注railscasts 196集，我尝试了他所做的一切，但我犯了以下错误

ActiveModel::MassAssignmentSecurity::Error in SurveysController#create
Can't mass-assign protected attributes: questions_attributes
Rails.root: /home/jean/rail/surveysays

这是到目前为止我的代码

调查表

<%= form_for(@survey) do |f| %>
  <% if @survey.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@survey.errors.count, "error") %> prohibited this survey from being saved:</h2>

      <ul>
      <% @survey.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :name %><br />
    <%= f.text_field :name %>
  </div>

  <%= f.fields_for :questions do |bf|%>
    <%= bf.label :content, "Question" %><br />
    <%= bf.text_area :content, :rows=> 3 %>
  <% end %>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

---

把你的课改成这个

class Survey < ActiveRecord::Base
  has_many :questions, :dependent => :destroy
  accepts_nested_attributes_for :questions
  attr_accessible :name, :questions_attributes
end

---

有关详细信息，请查找主题使用with attr_accessible

class Survey < ActiveRecord::Base
  has_many :questions, :dependent => :destroy
  accepts_nested_attributes_for :questions
  attr_accessible :name, :questions_attributes
end

---

查找使用attr_访问的主题以获取更多信息

它工作正常，我在另外6分钟内无法接受答案，同时这是ruby的新功能吗？它工作正常，我在另外6分钟内无法接受答案，同时这是ruby的新功能吗？

def new
    @survey = Survey.new
    3.times {@survey.questions.build }

    respond_to do |format|
      format.html # new.html.erb
      format.json { render json: @survey }
    end
  end

class Survey < ActiveRecord::Base
  has_many :questions, :dependent => :destroy
  accepts_nested_attributes_for :questions
  attr_accessible :name, :questions_attributes
end