title: Rails: Nothing produced by 3.times { model1.model2.build }
body: <p>I am following along with this <a href="http://railscasts.com/episodes/196-nested-model-form-part-1" rel="nofollow">Rails tutorial</a> describing how to do nested model forms. At 4:32, he starts describing how to prepopulate the form with three empty models. The two models in question are:</p>
  
  <pre><code>class Event &lt; ActiveRecord::Base
      has_many :positions, dependent: :destroy
      accepts_nested_attributes_for :positions
  end
  </code></pre>
  
  <p>And...</p>
  
  <pre><code>class Position &lt; ActiveRecord::Base
      belongs_to :event
  end
  </code></pre>
  
  <p>In my events controller, I added the tutorial's code to the <code>new</code> method</p>
  
  <pre><code>def new
    @event = Event.new
    3.times { @event.positions.build }
  end
  </code></pre>
  
  <p>And my event's form view is populated too.</p>
  
  <pre><code>&lt;!-- /apps/views/events/_form.html.erb --&gt;
  
  &lt;%= form_for(@event) do |f| %&gt;
    &lt;h3&gt;Event Details&lt;/h3&gt;
  
    &lt;div class="field"&gt;
      &lt;%= f.label :name %&gt;&lt;br&gt;
      &lt;%= f.text_field :name %&gt;
    &lt;/div&gt;
    &lt;!-- more fields here --&gt;
  
    &lt;h3&gt;Create positions for the event&lt;/h3&gt;
    &lt;% f.fields_for :positions do |builder| %&gt;
      &lt;p&gt;
        &lt;%= builder.label :name %&gt;
        &lt;%= builder.text_field :name %&gt;
      &lt;/p&gt;
      &lt;!-- more fields here --&gt;
    &lt;% end %&gt;
  
    &lt;!-- more fields here --&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>However, the <code>position</code> fields don't appear on my form. I've <code>rake db:migrated</code> and restarted the server (<code>Ctrl-C</code>, <code>rake s</code>) a bunch of times with no effect. What am I doing wrong?</p>