title: NotificationCenter issue on Swift 3
body: <p>I'm learning Swift 3 and I'm trying to using <code>NSNotificationCenter</code>. Here is my code: </p>
  
  <pre><code>func savePost(){
      let postData = NSKeyedArchiver.archivedData(withRootObject: _loadedpost)
      UserDefaults.standard().object(forKey: KEY_POST)
  }
  func loadPost(){
      if let postData = UserDefaults.standard().object(forKey: KEY_POST) as? NSData{
          if let postArray = NSKeyedUnarchiver.unarchiveObject(with: postData as Data) as? [Post]{
                  _loadedpost = postArray
          }
      }
      //codeerror
      NotificationCenter.default().post(NSNotification(name: "loadedPost" as NSNotification.Name, object: nil) as Notification)
  }
  </code></pre>
  
  <p>and this is the observer: </p>
  
  <pre><code>override func viewDidLoad() {
      super.viewDidLoad()
  //codeerorr
      NotificationCenter.default().addObserver(self, selector: Selector(("onPostLoaded")), name: "loadedPost", object: nil)
  }
  
  func numberOfSections(in tableView: UITableView) -&gt; Int {
      return 1
  }
  </code></pre>
  
  <p>It always gives me the error "signal SIGBRT". When I try to change the name in the observer, it's not an error, but obviously it didn't show anything. How do I fix this?</p>