升序判断，拼接参数

1：升序

NSArray * sra = [parDic.allKeys sortedArrayUsingComparator:^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2) {

        return [(NSString *)obj1 compare:obj2];
    }];
 2：   //拼接请求链接
    NSMutableString *parameUrl = [NSMutableString new];
    for (int i = 0; i < keys.count; i++) {
        NSString *key = [keys objectAtIndex:i];
        if (i == keys.count-1) {
            [parameUrl appendFormat:@"%@=%@",key,[parDic objectForKey:key]];
        }else{
            [parameUrl appendFormat:@"%@=%@&",key,[parDic objectForKey:key]];
        }
    }