swift - 正则表达式与textField保留两位小数

  func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        //        //第一个参数，被替换字符串的range，第二个参数，即将键入或者粘贴的string，返回的是改变过后的新str，即textfield的新的文本内容

        let oldText: NSString = textField.text! as NSString
        let checkStr = oldText.replacingCharacters(in: range, with: string)
        if checkStr.count == 0 {
            return true
        }
        if textField == self.tf_money{
            let regex = "^\\-?([1-9]\\d*|0)(\\.\\d{0,2})?$"
            let predicte = NSPredicate(format: "SELF MATCHES %@", regex)
            let isValid = predicte.evaluate(with: checkStr)
            return isValid
        }

        return true
    }