swift 3:单击后退导航按钮时如何绕过textFieldShouldEndEditing功能

class YourViewController: UIViewController, UITextFieldDelegate {
    // ...
    yourTextField.delegate = self
    // ...
}

class YourViewController: UIViewController, UITextFieldDelegate {
    // ...
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesBegan(touches, with: event)
        let touch = touches.first
        let touchPoint = touch?.location(in: self.view)
        
        if let backButtonFrame = self.navigationController?.navigationBar.backItem?.leftBarButtonItem?.customView?.frame,
           backButtonFrame.contains(touchPoint ?? CGPoint.zero) {
            yourTextField.resignFirstResponder()
        }
    }
    // ...
}