Swift判断金额只能输入.后面2位

    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        guard string == "." || string == "0" else {
            let newString = (textField.text! as NSString).replacingCharacters(in: range, with: string)

            let expression = "^[0-9]*((\\.|,)[0-9]{0,2})?$"
            let regex = try! NSRegularExpression(pattern: expression, options: NSRegularExpression.Options.allowCommentsAndWhitespace)
            let numberOfMatches = regex.numberOfMatches(in: newString, options:.reportProgress, range: NSMakeRange(0, (newString as NSString).length))
            return numberOfMatches != 0
        }
        guard let text = textField.text else { return true }
        if text.count == 0 {
            textField.text = "0."
            return false
        }
        if text.range(of: ".") != nil && string == "." {
            return false
        }
        if text.range(of: ".") != nil{
            let list = textField.text!.components(separatedBy: ".")
            let last = list.last!
            return (last as NSString).length < 2
        }
        return true
    }