title: How to get eventIdentifier from EKEvent store?
body: <p>Now i am working on EKEvent mange in calendar application.I successfully add an event to eventStore.I need to get an event identifier from event store. 
  I use the following code for access the eventIdentifier.But i always get null value for evetnIdentifier in my app.</p>
  
  <pre><code>EKEvent *event = [self eventAtIndexPath:indexPath];    
  NSString *eventIdentifier]; = [[NSString alloc] initWithFormat:@"%@",event.eventIdentifier];
  </code></pre>