ios控制异步顺序(group使用)

dispatch_group_t group = dispatch_group_create();
dispatch_group_enter(group);
[self networkGetBanners:group];
dispatch_group_enter(group);
[self networkGetNavigation:group];
dispatch_group_notify(group, dispatch_get_global_queue(0, 0), ^{
    NSLog(@"任务完成");
});

dispatch_group_leave(group);