unwind segue

- (UIStoryboardSegue *)segueForUnwindingToViewController:(UIViewController *)toViewController fromViewController:(UIViewController *)fromViewController identifier:(NSString *)identifier {
    if ([self.underLeftViewController isMemberOfClass:[toViewController class]] || [self.underRightViewController isMemberOfClass:[toViewController class]]) {
        ECSlidingSegue *unwindSegue = [[ECSlidingSegue alloc] initWithIdentifier:identifier source:fromViewController destination:toViewController];
        [unwindSegue setValue:@YES forKey:@"isUnwinding"];
        return unwindSegue;
    } else {
        return [super segueForUnwindingToViewController:toViewController fromViewController:fromViewController identifier:identifier];
    }
}