如：123456789

变为：123,456,789

直接上代码

+(NSString *)countNumAndChangeformat:(NSString *)num{    int count = 0;    long long int a = num.longLongValue;    while (a != 0)    {        count++;        a /= 10;    }    NSMutableString *string = [NSMutableString stringWithString:num];    NSMutableString *newstring = [NSMutableString string];    while (count > 3) {        count -= 3;        NSRange rang = NSMakeRange(string.length - 3, 3);        NSString *str = [string substringWithRange:rang];        [newstring insertString:str atIndex:0];        [newstring insertString:@"," atIndex:0];        [string deleteCharactersInRange:rang];    }    [newstring insertString:string atIndex:0];    return newstring;}