segueForUnwindingToViewController.m

- (UIStoryboardSegue *)segueForUnwindingToViewController:(UIViewController *)toViewController fromViewController:(UIViewController *)fromViewController identifier:(NSString *)identifier
{
    
    //how to set identifier for an unwind segue:
    
    //1. in storyboard -> documento outline -> select your unwind segue
    //2. then choose attribute inspector and insert the identifier name
    if ([@"UnwindFromSecondView" isEqualToString:identifier]) {
        return [[MyCustomUnwindSegue alloc] initWithIdentifier:identifier source:fromViewController destination:toViewController];
    }else {
    //if you want to use simple unwind segue on the same or on other ViewController this code is very important to mix custom and not custom segue
        return [super segueForUnwindingToViewController:toViewController fromViewController:fromViewController identifier:identifier];
    }
}