我想限制允许用户在UITextView中输入的字符数。为此，我使用委托方法shouldChangeTextInRange。
我现在遇到的问题是如何检测退格键逃逸。工作很好，但退格不。
如何检测退格键？
有什么想法吗？
这是我的代码

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool
    {
        if textField == biofield
        {
            if biofield.text == ""
            {
                self.countLbl.text = "0/40"
            }
            else
            {
                let count = self.biofield.text!.count + string.count
                print("Count is ", count)
                self.countLbl.text = "\(count)/40"
            }
            let maxLength = 40          // Set your need
            let currentString: NSString = biofield.text! as NSString
            let newString: NSString = currentString.replacingCharacters(in: range, with: string) as NSString
            return newString.length <= maxLength
            //return false
        }
        else
        {
            return true
        }
    }

非常感谢！