title: How to detect changes to Address Book after ABPersonViewController presentation
body: <p>I have two view controllers that allow changes to the Address Book.</p>
  
  <p>The first one lets you add or create an entry based on an ABRedordRef or edit an existing ABRecordRef, by presentation of either ABUnknownPersonViewController or ABPersonViewController.</p>
  
  <p>The second one is a standard ABPeoplePickerNavigationController that allows you to view/edit any of the contents of the Address Book.</p>
  
  <p>Both views are accessible easily accessible to the use via the main application UITabBarController.</p>
  
  <p>How can I determine that changes were made by either view controller, so that I can force data dependency changes to a third separate view controller.</p>
  
  <p>I thought that I saw a notification center message that I could subscribe to, but I can't seem to find it again...
  I don't care if the notification center is the method that should be used, or a delegate protocol or... whatever, I don't care, I just need to know how to detect the change or the need to re-sync with the Address Book.</p>
  
  <p>Can someone Please point me in the right direction.</p>
  
  <p>Thank you.</p>