iOS NSdata的部分数据转换成 字符串

• NSdata 转换成 字符串

- (NSString *)hexStringFromString:(NSData *)data{
    Byte *bytes = (Byte *)[data bytes];
    //下面是Byte转换为16进制。
    NSString *hexStr=@"";
    for(int i=0;i<[data length];i++){
        NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes[i]&0xff];///16进制数
        if([newHexStr length]==1)
            hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr];
        else
            hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr];
    }
    return hexStr;
}