多线程同步任务

GCD组任务三部曲，

1. 创建组
2. 创建队列（一般选择自定义串行、并行、或者全局）
3. 开启任务组任务
4. 监听notify回调，处理后续逻辑

   dispatch_group_t group = dispatch_group_create();
    dispatch_queue_t queue = dispatch_queue_create("queueByZxh", DISPATCH_QUEUE_SERIAL);

    dispatch_group_async(group, queue, ^{
        [NetWorkTool requestWithType:HttpRequestTypePost withHttpHeaderFieldDict:HYUSERTOKEN withUrlString:url withParaments:params withSuccessBlock:^(NSDictionary *responseObject) {
            NSLog(@"1111");
        } withFailureBlock:^(NSString *errorMsg) {
        } progress:^(float progress) {
        }];
    });

    dispatch_group_async(group, queue, ^{
        [Advertisement getAdsListByModelType:ModelType_ZHI_BO withResultBlock:^(NSDictionary *adverisementDict) {
            NSLog(@"2222");
        }];
    });
    
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        NSLog(@"3333");
    });
//实际输出是3333、1111/2222、2222/1111

//理想状态输出是 1111 、 2222、 3333，可并不是。 3333先输出了，因为AFN网络请求又开启了新的异步线程，所以要增加信号量控制

 dispatch_group_t group = dispatch_group_create();
    dispatch_queue_t queue = dispatch_queue_create("queueByZxh", DISPATCH_QUEUE_SERIAL);
    dispatch_group_async(group, queue, ^{
        dispatch_semaphore_t sem = dispatch_semaphore_create(0);
        [NetWorkTool requestWithType:HttpRequestTypePost withHttpHeaderFieldDict:HYUSERTOKEN withUrlString:url withParaments:params withSuccessBlock:^(NSDictionary *responseObject) {
            NSLog(@"1111");
            dispatch_semaphore_signal(sem);
        } withFailureBlock:^(NSString *errorMsg) {
            dispatch_semaphore_signal(sem);
        } progress:^(float progress) {
        }];
        dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
    });

    dispatch_group_async(group, queue, ^{
        dispatch_semaphore_t sem = dispatch_semaphore_create(0);
        [Advertisement getAdsListByModelType:ModelType_ZHI_BO withResultBlock:^(NSDictionary *adverisementDict) {
            NSLog(@"2222");
            dispatch_semaphore_signal(sem);
        }];
        dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
    });
    
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        NSLog(@"3333");
    });

//实际输出 最后执行的3333