title: Determine which object posted a notification?
body: <p>I'm having trouble identifying how to tell which object posted a notification.</p>
  
  <p>I subscribe to a notification in <strong>object A</strong>:</p>
  
  <pre><code>[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(receivedNotification:) name=@"ReceivedData" object:nil]
  </code></pre>
  
  <p>I post a notification from <strong>object B</strong>:</p>
  
  <pre><code>[[NSNotificationCenter defaultCenter] postNotificationName:@"ReceivedData" object: self userInfo: dict];
  </code></pre>
  
  <p>I recieve the notification in <strong>object A</strong>:</p>
  
  <pre><code>- (void) receivedNotification: (NSNotification*) notification
  {
     // Method is hit fine, notification object contains data.
  }
  </code></pre>
  
  <p>How can I tell that it was <strong>object B</strong> that sent the data and not, for instance, a <strong>object C</strong>?  I need a reference to the sender.  I don't want to add the sender to the notification object being passed, as I am specifiying the sender when I call the notification in <strong>object B</strong></p>