GCD多个接口请求完之后刷新UI

- (void)loadHttpData {

    dispatch_group_t group = dispatch_group_create();

    dispatch_queue_t searialQueue = dispatch_queue_create("com.hmc.www", DISPATCH_QUEUE_SERIAL);

    dispatch_group_enter(group);

    dispatch_group_async(group, searialQueue, ^{

        //网络请求1

        //成功失败 离开组

        dispatch_group_leave(group);

    });

    dispatch_group_enter(group);

    dispatch_group_async(group, searialQueue, ^{

        //网络请求2

        //成功失败 离开组

        dispatch_group_leave(group);

    });

    dispatch_group_enter(group);

    dispatch_group_async(group, searialQueue, ^{

        //网络请求3

        //成功失败 离开组

        dispatch_group_leave(group);

    });

    //三个网络请求结束，更新UI

    dispatch_group_notify(group, searialQueue, ^{

        dispatch_async(dispatch_get_global_queue(0, 0), ^{

            dispatch_async(dispatch_get_main_queue(), ^{

                //更新UI

            });

        });

    });

}