iOS开发NSString篇：字符串每隔几个字符插入某个字符

e.g

卡号：1234567890123456789
需求：将该卡号每四个字符用空格分隔
结果：1234 5678 9012 3456 789

算法思路：

遍历字符串，每隔4个字符插入一个空格

iOS代码实现：

//每隔4个字符添加一个空格的字符串算法- (NSString *)dealWithString:(NSString *)number{    NSString *doneTitle = @"";    int count = 0;    for (int i = 0; i < number.length; i++) {        count++;        doneTitle = [doneTitle stringByAppendingString:[number substringWithRange:NSMakeRange(i, 1)]];        if (count == 4) {            doneTitle = [NSString stringWithFormat:@"%@ ", doneTitle];            count = 0;        }    }    NSLog(@"%@", doneTitle);    return doneTitle;}