[ios] UINavigationBar Hide back Button Text

Swift version, works perfectly globally:

 func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {

        UIBarButtonItem.appearance().setTitleTextAttributes([NSForegroundColorAttributeName:UIColor.clearColor()], forState: UIControlState.Normal)
        UIBarButtonItem.appearance().setTitleTextAttributes([NSForegroundColorAttributeName:UIColor.clearColor()], forState: UIControlState.Highlighted)

        return true
    }