多个请求加载完成后，才做进一步操作，用到了dispatch_semaphore_t

不多说直接上代码

// 已经同意并且加入群组后的回调
- (void)didAcceptInvitationFromGroup:(EMGroup *)group
                               error:(EMError *)error
{
    dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
    __block NSString *aliasName;
    dispatch_group_t group1 = dispatch_group_create();
    dispatch_group_async(group1, dispatch_get_global_queue(0,0), ^{
        // 并行执行的线程一
        NSString *identify = [NSString stringWithFormat:@"%@",[[NSUserDefaults standardUserDefaults] objectForKey:@"identifySaves"]];
        NSMutableDictionary *dic = [NSMutableDictionary new];
        [dic setValue:[ToolUtils readToken]  forKey:@"token"];
        [dic setValue:[ToolUtils getPreferredLanguage] forKey:@"lang"];
        [dic setValue:identify forKey:@"id"];

        [AFHttpManager postJSONWithUrl: MainUrl(@"/im/getInfoById")  parameters:dic success:^(id responseObject) {
            if (responseObject) {
                NSNumber *cid = [[responseObject objectForKey:@"opResult"] objectForKey:@"retCode"];
                if ([cid intValue] == Success) {
                    NSArray *arr = [responseObject objectForKey:@"PersonInfo"];
                    NSDictionary* Datadic;
                    if (arr.count>0) {
                        Datadic = arr[0];
                    }
                    NSString *str = [Datadic objectForKey:@"aliasName"];
                    aliasName = str;

                    //请求成功，获取完昵称，  发送一个信号
                    dispatch_semaphore_signal(semaphore);
                }
            }
        } failure:^(NSError *error) {
            aliasName = identify;
        }];
    });
    
    __block NSInteger blockType = 1;
    dispatch_group_async(group1, dispatch_get_global_queue(0,0), ^{
        // 并行执行的线程二
        NSMutableDictionary *dic = [NSMutableDictionary new];
        [dic setValue:[ToolUtils readToken]  forKey:@"token"];
        [dic setValue:group.groupId forKey:@"imname"];//[array componentsJoinedByString:@","] forKey:@"imname"];
        [dic setValue:@"2" forKey:@"type"];
        [dic setValue:[ToolUtils getPreferredLanguage] forKey:@"lang"];
        [AFHttpManager postJSONWithUrl:MainUrl(Post_imGetListInfo) parameters:dic success:^(id responseObject) {
            [[BaseViewController sharedManager] waitView].hidden = YES;
            if (responseObject) {
                //  注意要加限制
                NSNumber *cid = [[responseObject objectForKey:@"opResult"] objectForKey:@"retCode"];
                if([cid intValue] == Success){
                    NSString *ID;
                    for( NSDictionary *findAllInfo in [responseObject objectForKey:@"findAllInfo"]){
                        ID = [[findAllInfo objectForKey:@"id"] stringValue];
                    }
                    NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
                    [dict setValue:[ToolUtils readToken]  forKey:@"token"];
                    [dict setValue:ID forKey:@"id"];
                    [dict setValue:[ToolUtils getPreferredLanguage] forKey:@"lang"];
                    [AFHttpManager postJSONWithUrl:MainUrl(Post_imLookGroupInfo) parameters:dict success:^(id responseObject) {
                        if (responseObject) {
                            NSNumber *cid = [[responseObject objectForKey:@"opResult"] objectForKey:@"retCode"];
                            if ([cid intValue] == Success) {
                                blockType = [[responseObject objectForKey:@"type"] integerValue];

                                //获取blockType的判定条件， 发送另一个信号
                                dispatch_semaphore_signal(semaphore);
                            }
                        }
                    } failure:^(NSError *error) {

                    }];
                }
            }
        } failure:^(NSError *error) {

        }];

    });
    
    dispatch_group_notify(group1,dispatch_get_global_queue(0, 0), ^{
        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);//信号量 -1
        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);//信号量 -1

        //注意：    n个 dispatch_semaphore_signal(semaphore)  
        // 要对应   n个 dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);

        //汇总结果
        EMChatText *txtChat;
        if (blockType == 1) {//请求获取的  aliasName  和判定条件  blockType
            txtChat = [[EMChatText alloc] initWithText:[NSString stringWithFormat:@"%@加入了群",aliasName]];
        }
        
        //环信发送消息的方法
        EMTextMessageBody *body = [[EMTextMessageBody alloc] initWithChatObject:txtChat];
        NSDictionary *loginInfo = [[[EaseMob sharedInstance] chatManager] loginInfo];
        NSString *username = [loginInfo objectForKey:kSDKUsername];
        EMMessage *message = [[EMMessage alloc] initWithReceiver:username bodies:@[body]];
        message.from = group.groupSubject;
        message.to = group.groupId;
        message.messageType = eConversationTypeGroupChat;// 设置为群聊消息
        message.deliveryState = eMessageDeliveryState_Delivered;
        message.ext = @{@"action":@"join_group"};
        [[EaseMob sharedInstance].chatManager asyncResendMessage:message progress:nil];
     });
}