NSString *originStr=@"lazazaA";
        NSMutableString *targetStr=[NSMutableString stringWithCapacity:20];
        for (long i=[originStr length]-1;i>=0;i--)
        {
            NSRange rng=NSRangeFromString([NSString stringWithFormat:@"这是location:%ld 这是长度：1}",i]);
            NSLog(@"%@",NSStringFromRange(rng));
            NSString *subStr = [originStr substringWithRange:rng];
            [targetStr appendString:subStr];
        }
        NSLog(@"%@",targetStr);

输出的结果为：
2013-07-24 16:35:35.803 Model[2978:303] {6, 1}
2013-07-24 16:35:35.804 Model[2978:303] {5, 1}
2013-07-24 16:35:35.804 Model[2978:303] {4, 1}
2013-07-24 16:35:35.804 Model[2978:303] {3, 1}
2013-07-24 16:35:35.804 Model[2978:303] {2, 1}
2013-07-24 16:35:35.805 Model[2978:303] {1, 1}
2013-07-24 16:35:35.805 Model[2978:303] {0, 1}
2013-07-24 16:35:35.805 Model[2978:303] Aazazal

求知道代码意思， substringWithRange rang 返回子字符串及 appendString: nsstring 在接受者的末尾附加nsstring的意思。也不知道怎么问，就想知道这些逐句的用处意思……