TopMostViewController

UIViewControllerExtensions.swift

import UIKit

extension UIViewController {

    /// Returns the current application's top most view controller.
    public class func topMostViewController() -> UIViewController? {
        let rootViewController = UIApplication.sharedApplication().windows.first?.rootViewController
        return self.topMostViewControllerOfViewController(rootViewController)
    }

    /// Returns the top most view controller from given view controller's stack.
    class func topMostViewControllerOfViewController(viewController: UIViewController?) -> UIViewController? {
        // presented view controller. It should be considered at the first.
        if let presentedViewController = viewController?.presentedViewController {
            return self.topMostViewControllerOfViewController(presentedViewController)
        }

        // UITabBarController
        if let tabBarController = viewController as? UITabBarController,
           let selectedViewController = tabBarController.selectedViewController {
            return self.topMostViewControllerOfViewController(selectedViewController)
        }

        // UINavigationController
        if let navigationController = viewController as? UINavigationController,
           let visibleViewController = navigationController.visibleViewController {
            return self.topMostViewControllerOfViewController(visibleViewController)
        }

        // child view controller
        for subview in viewController?.view?.subviews ?? [] {
            if let childViewController = subview.nextResponder() as? UIViewController {
                return self.topMostViewControllerOfViewController(childViewController)
            }
        }

        return viewController
    }

}