iOS 字符串数字中整数位，每三位添加一个逗号

- (NSString *)insetDouhao:(NSString *)str{    NSString *intStr;    NSString *floStr;    if ([strcontainsString:@"."]) {        NSRange range = [strrangeOfString:@"."];         floStr = [str substringFromIndex:range.location];         intStr = [str substringToIndex:range.location];    }else{        floStr = @"";        intStr = str;    }    if (intStr.length <=3) {        return [intStrstringByAppendingString:floStr];    }else{        NSInteger length = intStr.length;        NSInteger count = length/3;        NSInteger y = length%3;        NSString *tit = [intStrsubstringToIndex:y] ;        NSMutableString *det = [[intStrsubstringFromIndex:y] mutableCopy];        for (int i =0; i < count; i ++) {            NSInteger index = i + i *3;            [det insertString:@","atIndex:index];        }        if (y ==0) {            det = [[det substringFromIndex:1]mutableCopy];        }        intStr = [tit stringByAppendingString:det];        return [intStrstringByAppendingString:floStr];    }}