nested models in rails 3

nested models

/models/survey.erb
class Survey < ActiveRecord::Base
  has_many :questions, :dependent => :destroy
  accepts_nested_attributes_for :questions
  validates_presence_of :name
end

/models/question.erb
class Question < ActiveRecord::Base
  belongs_to :survey
  validates_presence_of :content
end

/controllers/surveys_controller.rb
  def new
    @survey = Survey.new
    @survey.questions.build

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



/views/survey/_form.html.erb
<%= 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>
  <h3>Add new question</h3>
  <% f.fields_for :questions do |p| %>
    <%= p.label :content, "Questions" %><br />
    <%= p.text_area :content, :rows => 3 %>
  <% end %>
  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>