title: Notification center method method called multiple time ios in Tab bar (View controller)? How to remove observer?
body: <p>I am posting notification form one view controller which is in navigation stack in tab bar application. I am removing observer in dealloc as.  </p>
  
  <pre><code> [[NSNotificationCenter defaultCenter] removeObserver:self name:@"ArtworkAddedReloadAllArtworks" object:nil];  in dealloc correctly.
  </code></pre>
  
  <p>I am logout as</p>
  
  <pre><code>[[self tabBarController] dismissViewControllerAnimated:YES completion:nil];
  </code></pre>
  
  <p>but issue is when i login back same notification added twice as in Notification center</p>
  
  <pre><code>ArtworkAddedReloadAllArtworks, 0x12ff698, 0x7a490e00, 1400
  ArtworkAddedReloadAllArtworks, 0x12ff698, 0x7a431800, 1400
  </code></pre>
  
  <p>In Notification center as 2 instance of view controller is created and notification added twice two different objects, How do i unregister notification ? i cant remove from viewDidDisappear as i posting notification from other controller.dealloc is calling after login. </p>
  
  <p>How to make nil view controller(created first before login),and his observer?</p>
  
  <p>Thanks in advance.  </p>