preferredStatusBarStyle() to work within UINavigationController and UITabBarController

UITabBarController+UINavigationController.swift

extension UITabBarController {
   open override var childForStatusBarStyle: UIViewController? {
        return selectedViewController
    }
}

extension UINavigationController {
   open override var childForStatusBarStyle: UIViewController? {
        return visibleViewController
    }
}

// MARK: - Usage
class ViewController: UIViewController {

    // This will be called every time the ViewController appears
    // Works great for pushing & popping with navigation or switch tabBar item
    override var preferredStatusBarStyle: UIStatusBarStyle {
        return .lightContent
    }

}