How to swizzle viewDidLoad method in UIViewController in swift 4? initialize() is deprecated in swift 4

I want to swizzle viewDidLoad in a UIViewController extension but initialize() method which was overridden in swift3 and was working is not supported by swift4. Can anyone give me any solution to this? My code in swift3 was as below.

    extension UIViewController {

    open override class func initialize() {

        guard self === UIViewController.self else { return }
        swizzling(self)
    }

    // MARK: - Method Swizzling

    func nsh_viewDidLoad() {
        self.nsh_viewDidLoad()

        self.navigationItem.backBarButtonItem = UIBarButtonItem(title: "", style: .plain, target: nil, action: nil)
    }
    }

and have a global method

private let swizzling: (UIViewController.Type) -> () = { viewController in

    let originalSelector = #selector(viewController.viewDidLoad)
    let swizzledSelector = #selector(viewController.nsh_viewDidLoad)

    let originalMethod = class_getInstanceMethod(viewController, originalSelector)
    let swizzledMethod = class_getInstanceMethod(viewController, swizzledSelector)

    let didAddMethod = class_addMethod(viewController, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))

    if didAddMethod {
        class_replaceMethod(viewController, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod))
    } else {
        method_exchangeImplementations(originalMethod, swizzledMethod)
    }
}

I added the below code in AppDelegate instead if swizzling

let barButtonItemAppearance = UIBarButtonItem.appearance()
        barButtonItemAppearance.setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor.clear], for: .normal)
        barButtonItemAppearance.setTitleTextAttributes([NSAttributedStringKey.foregroundColor: UIColor.clear], for: .highlighted)