本片分两部分

1、使用正则表达式过滤表情
2、处理苹果自带键盘无法输入汉字问题

先记录下，后面完善：

override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        
        NotificationCenter.default.addObserver(self, selector: #selector(self.textFieldEditChanged(noti:)), name: Notification.Name.UITextFieldTextDidChange, object: self.inputTextField)
    }
    
    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
        
        NotificationCenter.default.removeObserver(self, name: Notification.Name.UITextFieldTextDidChange, object: self.inputTextField)
    }

@objc fileprivate func textFieldEditChanged(noti: Notification) {
        
        guard let textField = noti.object as? UITextField else {
            return
        }
        
        // 有高亮的正在输入的字符，不做任何处理
        if let _ = textField.markedTextRange {
            return
        }
        
        guard let endRange = textField.selectedTextRange?.end else {
            return
        }
        
        guard let regexStr = self.stepType.inputRegex else {
            return
        }
        
        let cursorPositon = textField.offset(from: textField.endOfDocument, to: endRange)
        
        // 使用正则过滤字符串
        let resultStr = Utils.regularRepalce(regexStr, origin: textField.text ?? "")
        textField.text = resultStr
        
        if let targetPosition = textField.position(from: textField.endOfDocument, offset: cursorPositon) {
            textField.selectedTextRange = textField.textRange(from: targetPosition, to: targetPosition)
        }
        
    }

使用给定的正则匹配，不匹配的字符使用空串过滤

 /// 对给入的字符串进行正则，未匹配的使用相应的字符替换
    ///
    /// - Parameters:
    ///   - regexStr: 正则
    ///   - origin: 原始字符串
    ///   - template: 喜欢的字符串
    /// - Returns: 返回正则处理之后的字符串
    public static func regularRepalce(_ regexStr: String, origin: String, template: String = "") -> String {
        
        guard let regex = try? NSRegularExpression(pattern: regexStr, options: []) else {
            return origin
        }
        return regex.stringByReplacingMatches(in: origin, options: [], range: NSRange(location: 0, length: origin.count), withTemplate: template)
        
    }

我使用的正则
1、匹配所有非 空格大小写字母数字中文和下划线 -

"[^ A-Za-z0-9\\u4E00-\\u9FA5_-]"                  // 中英文空格_-,其他过滤
"[^A-Za-z0-9]"    // 非英文数字