title: Getting undefined method for ActiveRecord::Relation
body: <p>I have the following models</p>
  
  <pre><code>class Book &lt; ActiveRecord::Base
    has_many :chapters
  end
  </code></pre>
  
  <p>and</p>
  
  <pre><code>class Chapter &lt; ActiveRecord::Base
      belongs_to :book
  end
  </code></pre>
  
  <p>in <code>/chapters/edit/id</code> I get</p>
  
  <pre><code>undefined method `book' for #&lt;ActiveRecord::Relation:0x0000010378d5d0&gt;
  </code></pre>
  
  <p>when i try to access book like this</p>
  
  <pre><code>@chapter.book
  </code></pre>