微信支付开发中走过的坑

• 写在前面的话：楼主现在一家小公司任职，公司一直没有招到满意的后台，所以楼主的微信支付所有的逻辑处理全部写在了前端，希望这篇文章能对那些跟楼主处境相似的伙伴们提供点思路。好了，进入正题

• 楼主自己总结的微信支付的基本步骤

• 1、获取订单的基本数据（字典类型的，一般就是订单价格、描述、详情等基础信息）

NSMutableDictionary *packageParams = [NSMutableDictionary dictionary];
    
    [packageParams setObject: APP_ID             forKey:@"appid"];       //开放平台appid
    [packageParams setObject: MCH_ID             forKey:@"mch_id"];      //商户号
    [packageParams setObject: @"APP-001"        forKey:@"device_info"]; //支付设备号或门店号
    [packageParams setObject: noncestr          forKey:@"nonce_str"];   //随机串
    [packageParams setObject: @"APP"            forKey:@"trade_type"];  //支付类型，固定为APP
    [packageParams setObject: body              forKey:@"body"];        //订单描述，展示给用户
    [packageParams setObject: @"www.baidu.com"  forKey:@"notify_url"];  //支付结果异步通知
    [packageParams setObject: orderID           forKey:@"out_trade_no"];//商户订单号
    [packageParams setObject: spbill_ip    forKey:@"spbill_create_ip"];//发器支付的机器ip
    [packageParams setObject: totalFee          forKey:@"total_fee"];  // 价格，微信价格单位是分，这点注意和支付宝区分

• 2、将上述基本数据字典，按照key=value的形式转换拼接成字符串
• 3、在第二步的字符串末尾拼接上key（商户API密钥）
• 4、MD5加密第三步生成的字符串，生成的是prePayid（在第五步中签名的作用），字符串类型

- (NSString*)createMd5Sign:(NSMutableDictionary*)dict
{
    NSMutableString *contentString  =[NSMutableString string];
    NSArray *keys = [dict allKeys];
    //按字母顺序排序
    NSArray *sortedArray = [keys sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
        return [obj1 compare:obj2 options:NSNumericSearch];
    }];
    //拼接字符串
    for (NSString *categoryId in sortedArray) {
        if (![[dict objectForKey:categoryId] isEqualToString:@""]
            && ![categoryId isEqualToString:@"sign"]
            && ![categoryId isEqualToString:@"key"]
            )
        {
            [contentString appendFormat:@"%@=%@&", categoryId, [dict objectForKey:categoryId]];
        }    
    }
    //添加key字段
    [contentString appendFormat:@"key=%@", PARTNER_key];
    //得到MD5 sign签名
    NSString *md5Sign =[NSString stringWithMD5:contentString];
    
    return md5Sign;
}

• 5、由于微信服务器希望我们传给它的是xml格式的数据，所以我们需要把基本的字典数据（第一步中的字典）转换成xml格式，末尾用第四步中的字符串在进行签名，生成新的字符串

- (NSString *)getPackage:(NSMutableDictionary*)packageParams prePayString:(NSString *)sign
{
    NSMutableString *reqPars=[NSMutableString string];
    //生成xml的package
    NSArray *keys = [packageParams allKeys];
    [reqPars appendString:@"\n"];
    for (NSString *categoryId in keys) {
        [reqPars appendFormat:@"<%@>%@\n", categoryId, [packageParams objectForKey:categoryId],categoryId];
    }
    [reqPars appendFormat:@"%@\n", sign];
    
    return [NSString stringWithString:reqPars];
}

• 6、第5步生成的就是预支付订单，用它向微信服务器请求我们需要的订单

    NSString *urlStr = @"https://api.mch.weixin.qq.com/pay/unifiedorder";
    urlStr = [urlStr stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    
    NSURL *url = [NSURL URLWithString:urlStr];
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:5];
    request.HTTPMethod = @"POST";
    //设置数据类型
    [request addValue:@"text/xml" forHTTPHeaderField:@"Content-Type"];
    //设置编码
    [request setValue:@"UTF-8" forHTTPHeaderField:@"charset"];
    //如果是POST
    [request setHTTPBody:[orderString dataUsingEncoding:NSUTF8StringEncoding]];
    NSURLSession *session = [NSURLSession sharedSession];
    NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {

}];

• 7、将请求下来的数据转成字典数据,这个data就是第6步中的data

  NSString *xmlStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
  NSDictionary *dic = [NSDictionary dictionaryWithXMLString:xmlStr];

• 8、判断return_code和``result_code都是成功的，我们再从字典取出prepay_id`对应的值

• 8、重新拼接生成一个字典属性（里面有7个键值对）大概和上面前3部一样，也是先字典转字符串md5加密，签名

                NSString *package, *time_stamp, *nonce_str;
                //设置支付参数
                time_t now;
                time(&now);
                time_stamp  = [NSString stringWithFormat:@"%ld", now];
                nonce_str = [NSString stringWithMD5:time_stamp];
                package         = @"Sign=WXPay";
                //第二次签名参数列表
                NSMutableDictionary *signParams = [NSMutableDictionary dictionary];
                [signParams setObject: APP_ID        forKey:@"appid"];
                [signParams setObject: nonce_str    forKey:@"noncestr"];
                [signParams setObject: package      forKey:@"package"];
                [signParams setObject: MCH_ID        forKey:@"partnerid"];
                [signParams setObject: time_stamp   forKey:@"timestamp"];
                [signParams setObject: prePayid     forKey:@"prepayid"];
                /**
                 *  把
                 */
                NSString *signStr = [self createMd5Sign:signParams];
                [signParams setObject:signStr forKey:@"sign"];

• 9、把重新生成的字典传回去

 resultblock(signParams, nil);

• 10、这个字典中就和微信给我们的类中需要的信息一一对应起来了，这样就可以吊起微信支付了

• 11、最后给个Demo，里面有支付宝和微信两种支付

[我是链接][1]
[1]:https://github.com/liyang123/LYPayDemo.git