title: Send and receive messages through NSNotificationCenter in swift?
body: <p>I need a simple example program to send and receive a message through NSNotificationCenter in Swift? 
  Im using core audio and I need to notify my app if the head phones are removed while I am playing audio. I don't know if I should add the observer in the app delegate or in my view since I have to keep playing audio in background.  </p>
  
  <p>This is the function that I use to control the route change to know if the headphones are removed.</p>
  
  <pre><code>-(void)handleRouteChange:(NSNotification *)notif
  {
     NSDictionary *dict = notif.userInfo;
     AVAudioSessionRouteDescription *routeDesc = dict[AVAudioSessionRouteChangePreviousRouteKey];
     AVAudioSessionPortDescription *prevPort = [routeDesc.outputs objectAtIndex:0];
     if ([prevPort.portType isEqualToString:AVAudioSessionPortHeadphones]) {
          //Head phone removed
        }
   }
  </code></pre>