为每个视图控制器指定后退按钮的行为

func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
    let backButton = UIBarButtonItem(title: "返回", style: .plain, target: self, action: #selector(backButtonPressed))
    viewController.navigationItem.backBarButtonItem = backButton
}

@objc func backButtonPressed() {
    // 执行自定义的后退按钮行为
    // 例如，保存表单数据或者执行其他操作
}

override func viewDidLoad() {
    super.viewDidLoad()

    let backButton = UIBarButtonItem(title: "返回", style: .plain, target: self, action: #selector(backButtonPressed))
    navigationItem.backBarButtonItem = backButton
}

@objc func backButtonPressed() {
    // 执行特定的后退按钮行为
    // 例如，返回上一个页面或者执行其他操作
}