Xcode iPhone/iPad find the top View Controller in the current View Hierarchy

There are three possiblities. 

Case 1: If the view controller is embedded in UINavigationController

Case 2: If the view controller is embedded in UITabControllerBar

Case 3: If the view controller is presented  via other UIViewController

So we have to traverse through the possible combination until we reach the topmost layer.

#pragma mark- View Hierarchy-

+ (UIViewController*)topViewController {

    return [self topViewControllerWithRootViewController:[UIApplication sharedApplication].keyWindow.rootViewController];

}

+ (UIViewController*)topViewControllerWithRootViewController:(UIViewController*)rootViewController {

//Type 1: Travese in tabbar controller-

    if ([rootViewController isKindOfClass:[UITabBarController class]]) {

        UITabBarController* tabBarController = (UITabBarController*)rootViewController;

        return [self topViewControllerWithRootViewController:tabBarController.selectedViewController];

//Type 2: Travese in navigation controller-

    } else if ([rootViewController isKindOfClass:[UINavigationController class]]) {

        UINavigationController* navigationController = (UINavigationController*)rootViewController;

        return [self topViewControllerWithRootViewController:navigationController.visibleViewController];

//Type 3: Travese in view controller-

    } else if (rootViewController.presentedViewController) {

        UIViewController* presentedViewController = rootViewController.presentedViewController;

        return [self topViewControllerWithRootViewController:presentedViewController];

    } else {

        return rootViewController;

    }

}