隐藏导航按钮

Question

我有一个简单的应用程序，允许用户通过相机胶卷从他们的设备中选择图像或拍摄新图像。容易。

我有两个按钮;

名为Set Image的导航栏上的

1）将图像保存到核心数据

打开图像选择器控制器的主视图上的

2）。

我的问题;

如果图片选择 不 ，如何隐藏导航栏上的按钮？

    import UIKit

class CameraRollViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

    @IBOutlet weak var imageView: UIImageView!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
    }

    override func viewWillAppear(_ animated: Bool) {

        self.navigationController?.navigationBar.setBackgroundImage(UIImage(),for: .default)
        self.navigationController?.navigationBar.shadowImage = UIImage()
        self.navigationController?.navigationBar.isTranslucent = true

    }

    @IBAction func addImage(_ sender: Any) {
        let imagePickerController = UIImagePickerController()
        imagePickerController.delegate = self

        let actionSheet = UIAlertController(title: "Lets customize your Reminders Page", message: "Choose a source", preferredStyle: .actionSheet)

        actionSheet.addAction(UIAlertAction(title: "Camera", style: .default, handler: { (action:UIAlertAction) in

            if UIImagePickerController.isSourceTypeAvailable(.camera) {
                imagePickerController.sourceType = .camera
                self.present(imagePickerController, animated: true, completion: nil)
            }else{
                print("Camera not available")
            }


        }))

        actionSheet.addAction(UIAlertAction(title: "Photo Library", style: .default, handler: { (action:UIAlertAction) in
            imagePickerController.sourceType = .photoLibrary
            self.present(imagePickerController, animated: true, completion: nil)
        }))

        actionSheet.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))

        self.present(actionSheet, animated: true, completion: nil)


    }

    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
        let image = info[UIImagePickerControllerOriginalImage] as! UIImage

        imageView.image = image

        picker.dismiss(animated: true, completion: nil)
    }

    func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
        picker.dismiss(animated: true, completion: nil)
    }


    }

任何人都知道如何做到这一点？