title: Doctrine - preUpdate invokes but doesn't change a related entity property while prePersist does
body: <p>I am bit new to Doctrine, I found LifeCycleCallback quite useful but when I implemented I found this lacking : </p>
  
  <p>I have an Author -> Book one-to-many relationship, I put <code>prePersist</code> and <code>preUpdate</code> <code>lifecyclecallback</code> event in book entity so that a property on Author entity can get changed. But I found prePersist works fine but preUpdate not able to make changes to related entity. Am I missing something here or should I register an <a href="http://symfony.com/doc/current/cookbook/doctrine/event_listeners_subscribers.html" rel="nofollow">Event Listener &amp; Subscriber</a> for a change in related Entity property?</p>
  
  <p>Note : I am following the <a href="http://symfony.com/doc/current/book/doctrine.html#lifecycle-callbacks" rel="nofollow">Symfony doc on simple lifecycle callback</a>.</p>
  
  <p><strong>Some code snippets :</strong></p>
  
  <p>Book mapping to Author &amp; Life cycle callback :</p>
  
  <pre><code>&lt;many-to-one field="author" target-entity="Author" inversed-by="books"&gt;
      &lt;join-columns&gt;
          &lt;join-column name="author_id" referenced-column-name="id"/&gt;
      &lt;/join-columns&gt;
  &lt;/many-to-one&gt;
  &lt;lifecycle-callbacks&gt;
      &lt;lifecycle-callback type="prePersist" method="prePersistAction" /&gt;
      &lt;lifecycle-callback type="preUpdate" method="preUpdateAction" /&gt;
  &lt;/lifecycle-callbacks&gt;
  </code></pre>
  
  <p>Author mapping to Book</p>
  
  <pre><code>&lt;one-to-many field="books" target-entity="Book" mapped-by="author"&gt;&lt;/one-to-many&gt;
  </code></pre>
  
  <p>On Book entity I added 2 methods to response event callback :</p>
  
  <pre><code>/**
   * On prePersist Event. 
   */
  public function prePersistAction()
  {
      $this-&gt;name = 'Some new name here';
      $this-&gt;author-&gt;setName('new Author name as per book');
  }
  /**
   * On preUpdate Event.
   */
  public function preUpdateAction()
  {
      $this-&gt;name = 'Some new name here';
      $this-&gt;author-&gt;setName('new Author name as per book');
  }
  </code></pre>