Tag를 이용한 delegate 에서의 분기문

http://www.idev101.com/code/User_Interface/UIAlertView.html

   UIAlertView *alert = [[[UIAlertView alloc] initWithTitle:@"Error" message:@"I'm sorry Dave, I'm afraid I can't do that." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil] autorelease];
    [alert setTag:12];
    [alert show];

... later ...

- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {
    if ([alertView tag] == 12) {    // it's the Error alert
        if (buttonIndex == 0) {     // and they clicked OK.
            // do stuff
        }
    }
}