在应用程序出口上关闭模态视图控制器

self.dismiss(animated: true, completion: nil)

protocol ModalViewControllerDelegate: class {
    func closeModalViewController()
}

weak var delegate: ModalViewControllerDelegate?

@IBAction func closeButtonTapped(_ sender: UIButton) {
    delegate?.closeModalViewController()
}

extension ParentViewController: ModalViewControllerDelegate {
    func closeModalViewController() {
        dismiss(animated: true, completion: nil)
    }
}

@IBAction func closeButtonTapped(_ sender: UIButton) {
    NotificationCenter.default.post(name: NSNotification.Name("CloseModalViewController"), object: nil)
}

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: #selector(closeModalViewController), name: NSNotification.Name("CloseModalViewController"), object: nil)
}

@objc func closeModalViewController() {
    dismiss(animated: true, completion: nil)
}