disabling autorotate

ViewController.Swift

class MainNavigationController: UINavigationController {
  
    // autorotate by top viewController 
    override var shouldAutorotate: Bool {
        if !viewControllers.isEmpty {
            return self.topViewController!.shouldAutorotate
        } else {
            return true
        }
    }
    
    // orientation by top viewController
    override var supportedInterfaceOrientations: UIInterfaceOrientationMask{
        if !viewControllers.isEmpty {
            return self.topViewController!.supportedInterfaceOrientations
        } else {
            return self.supportedInterfaceOrientations
        }
    }

}
  

class ViewController: UIViewController {
   
    // disable autoratation
    override var shouldAutorotate : Bool {
        return false
    }
  
    //only portrait allowed 
    override var supportedInterfaceOrientations : UIInterfaceOrientationMask {
        return UIInterfaceOrientationMask.portrait
    }
  
}