如何掩盖Swift中的最后一个数字？

func hideLastDigit(_ number: Int) -> String {
    let numberString = String(number)
    
    if let lastDigitIndex = numberString.index(numberString.endIndex, offsetBy: -1, limitedBy: numberString.startIndex) {
        let substring = numberString[numberString.startIndex..<lastDigitIndex]
        let hiddenString = substring + "*"
        return hiddenString
    } else {
        return ""
    }
}

// 示例用法
let number = 123456
let hiddenNumber = hideLastDigit(number)
print(hiddenNumber)  // 输出: "12345*"