title: m2m_changed Signal in django
body: <p>I have two apps, A and B</p>
  
  <p>The models.py of A is:-</p>
  
  <pre><code>class Channel(models.Model):
      user = models.ForeignKey(User,unique=True)
      name = models.CharField(max_length=100)
      events = models.ManyToManyField(Event,null=True,blank=True)
  
      def __unicode__(self):
          return self.name
  </code></pre>
  
  <p>The models.py of B is:-</p>
  
  <pre><code>class Event(models.Model):
      name = models.CharField(max_length=100)
  
      def __unicode__(self):
          return self.name
  </code></pre>
  
  <p>I am trying to use m2m_changed Signal to do something whenever a new event is added to a given Channel instance. </p>
  
  <p>The problem is that i am unable to find a way to know the id of the event, when it is added to an instance of Channel.
  I checked the docs :- 
  <a href="https://docs.djangoproject.com/en/dev/ref/signals/" rel="nofollow">https://docs.djangoproject.com/en/dev/ref/signals/</a></p>
  
  <p>There is pk_set . But the problem is that it is showing the ids of previously added events as well , when i add a new event to a given instance of Channel. I just want to know the id of latest added event.</p>
  
  <p>How is this possible?
  Hope my question is clear...
  Thanks in advance :)</p>