Swift UItextField、UITextView限制字数

extension LUserInfoEditCtrl: UITextFieldDelegate,YYTextViewDelegate {
    
    //限制TF开头不能输入空格
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        if string == " " {
            return false
        }
        return true
    }
    
    @objc func tfDidChange(textField: UITextField) {
        let maxLength = 10
        let toBeString : String = textField.text ?? ""
        let lang = textField.textInputMode?.primaryLanguage
        if lang == "zh-Hans" {
            //简体中文输入

            //获取高亮部分
            let selRange = textField.markedTextRange
            let position = textField.position(from: selRange!.start, offset: 0)

            //没有高亮选择的字，则对已输入的文字进行字数统计和限制
            if (position == nil) {
                if toBeString.count > maxLength {
                    textField.text = String(toBeString.prefix(maxLength))
                }
            }

        }else {
            //中文输入法以外的直接对其统计限制即可，不考虑其他语种情况
            if toBeString.count > maxLength {
                let aaa = toBeString as NSString
                let rangeIndex = aaa.rangeOfComposedCharacterSequence(at: maxLength)
                if rangeIndex.length == 1 {
                    textField.text = String(toBeString.prefix(maxLength))
                }else {
                    let rangeRange = aaa.rangeOfComposedCharacterSequences(for: NSMakeRange(0, maxLength))
                    textField.text = aaa.substring(with: rangeRange)
                }
            }
        }
        
        nameCountLab.text = "\(textField.text?.count ?? 0)/10"
    }
    
    
    func textViewDidChangeSelection(_ textView: YYTextView) {
        let num = textView.text.count
        let maxLength = 50
        if num > maxLength {
            textView.text = String(textView.text.prefix(maxLength))
        }
        
        infoCountLab.text = "\(num)/\(maxLength)"
    }
    
    
}