Call viewcontroller from Appdelegate or UIView

- (UIViewController *)visibleViewController:(UIViewController *)rootViewController

{

    if (rootViewController.presentedViewController == nil)

    {

        return rootViewController;

    }

    if ([rootViewController.presentedViewController isKindOfClass:[UINavigationController class]])

    {

        UINavigationController *navigationController = (UINavigationController *)rootViewController.presentedViewController;

        UIViewController *lastViewController = [[navigationController viewControllers] lastObject];

        

        return [self visibleViewController:lastViewController];

    }

    if ([rootViewController.presentedViewController isKindOfClass:[UITabBarController class]])

    {

        UITabBarController *tabBarController = (UITabBarController *)rootViewController.presentedViewController;

        UIViewController *selectedViewController = tabBarController.selectedViewController;

        

        return [self visibleViewController:selectedViewController];

    }

    UIViewController *presentedViewController = (UIViewController *)rootViewController.presentedViewController;

    

    return [self visibleViewController:presentedViewController];

}

// Call viewcontroller

       UIViewController *vc = [self visibleViewController:[UIApplication sharedApplication].keyWindow.rootViewController];

        

        NextViewController *next = [[NextViewController alloc]initWithNibName:@"NextViewController" bundle:nil];

        [vc presentViewController:next animated:YES completion:nil];