微信支付集成相关的东西我就不在这里复述了，网上一大堆文章，大家搜索一下按照步骤应该都没啥问题，两个商户的回调处理我还没做，有时间会更新，废话不多说，直接开整

记得把2个商户号都填写到 URL Schemes中

1、在AppDelegation didFinishLaunchingWithOptions 中设置

1、注册通知
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(wechatPayResigerNotifi:) name:@"wechatPayResiger" object:nil];


2、通知回调
#pragma mark  -------------- 微信注册通知回调
- (void)wechatPayResigerNotifi:(NSNotification *)notifi
{
    NSDictionary *dict =notifi.userInfo;
    if ([dict[@"key"] intValue] == 1) {
        //.商户1
        [WXApi registerApp:@"wxx124124xx1241412"];

    } else {
        //.商户2
        [WXApi registerApp:@"wxx124124xx1242141"];
    }
}

2、在支付界面（或者自定义界面）中设置

dict中的参数是后台返回的参数（商户1，商户2全都用这一个方法就可以）

[[NSNotificationCenter defaultCenter] postNotificationName:@"wechatPayResiger" object:@"" userInfo:@{@"key" : @"1"}];
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
dict[@"partnerId"] = @"1";
dict[@"prepayId"] = @"2";
dict[@"nonceStr"] = @"3";
dict[@"api_key"] = @"4";
dict[@"timeStamp"] = @"5";
dict[@"appId"] = @"6";
[self wxpay:dict];

3、因为后台没有进行2次签名，所以前天做了2次签名，建议签名全部由后台做 ，我项目中是需要进行2次签名的，如果读者不需要2次签名，直接用后台返回的参数调起微信就可以

 记得导入 #import <CommonCrypto/CommonDigest.h>

- (void)wxpay:(NSDictionary *)wechatDic {
    time_t now;
    time(&now);
    NSString *timestamp = [NSString stringWithFormat:@"%ld",now];
    NSString *noncestr = [self md5:timestamp];
    NSDictionary *dict = @{
                           @"appid":[wechatDic objectForKey:@"appId"],
                           @"noncestr":noncestr,
                           @"package":@"Sign=WXPay",
                           @"partnerid":[wechatDic objectForKey:@"partnerId"],
                           @"prepayid":[wechatDic objectForKey:@"prepayId"],
                           @"timestamp":timestamp
                           };
    NSMutableString *contentString = [NSMutableString string];
    NSArray *keys = [dict allKeys];
    // 按照ASCII 码排序
    NSArray *sortedArray = [keys sortedArrayUsingComparator:^NSComparisonResult(id  _Nonnull obj1, id  _Nonnull obj2) {
        return [obj1 compare:obj2 options:NSNumericSearch];
    }];
    // 拼接字符串
    for (NSString *categoryId in sortedArray) {
        if (![[dict objectForKey:categoryId] isEqualToString:@""]&&![[dict objectForKey:categoryId] isEqualToString:@"key"]&&![[dict objectForKey:categoryId] isEqualToString:@"sign"]) {
            [contentString appendFormat:@"%@=%@&",categoryId,dict[categoryId]];
        }
    }
    
    // 添加商户key字段
    NSString *secretkey = [wechatDic objectForKey:@"api_key"];
    [contentString appendFormat:@"key=%@",secretkey];
    // 加密
    NSString *md5Sign = [self md5:contentString];
    // 支付数据
    PayReq *req = [[PayReq alloc] init];
    req.openID = [wechatDic objectForKey:@"appId"];
    req.partnerId = [wechatDic objectForKey:@"partnerId"];
    req.prepayId = [wechatDic objectForKey:@"prepayId"];
    req.package = @"Sign=WXPay";
    req.nonceStr = noncestr;
    req.timeStamp = [timestamp intValue];
    req.sign = md5Sign;
    [WXApi sendReq:req];
}

- (NSString *)md5:(NSString *)str {
    const char *cStr = [str UTF8String];
    unsigned char digest[CC_MD5_DIGEST_LENGTH];
    CC_MD5(cStr,(unsigned int)strlen(cStr),digest);
    NSMutableString *output = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i ++) {
        [output appendFormat:@"%02X",digest[i]];
    }
    return output;
}