组内异步会与组外顺序执行的事件争抢资源
1)、创建一个组
dispatch_group_t group = dispatch_group_create();
2)、组内异步ST1,DISPATCH_QUEUE_PRIORITY_DEFAULT 为默认优先级
dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ //do something 1 });
3)、组内异步ST2,DISPATCH_QUEUE_PRIORITY_DEFAULT 为默认优先级
dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ //do something 2 });
4)、组内通知,获取主线程。组内异步全部执行完就到这里
dispatch_group_notify(group, dispatch_get_main_queue(), ^{ //组内全部完成 再 do something });
5)、组外ST3
//do something 3