swift3字符串替换好像麻烦了不少
研究了一下才研究出这个方法，不知道还有没有更简便的办法

extension @H_403_5@String {
 /// 替换手机号中间四位
    ///
    /// - Returns: 替换后的值
    func replacePhone() -> @H_403_5@String {
        let start = @H_403_5@self@H_403_5@.index(@H_403_5@self@H_403_5@.startIndex,offsetBy: 3)
        let end = @H_403_5@self@H_403_5@.index(@H_403_5@self@H_403_5@.startIndex,offsetBy: 7)
        let range = Range(uncheckedBounds: (lower: start,upper: end))
        return @H_403_5@self@H_403_5@.replacingCharacters(in: range,with: "****")
    }
}

使用

let str:String = "13888888888"
print(str.replacePhone())
-------分割线
138****8888