MacOS 開發 — 線程依賴

• 等待多個異步函數執行完畢之後，在執行某段代碼

dispatch_group_t group = dispatch_group_create(); 

for (ALUser *user in self.users) { 
dispatch_group_enter(group); 
[ALFeed updateByUser:user completion:^{ 
dispatch_group_leave(group); 
}]; 
} 

dispatch_group_notify(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{ 
[self.tableView reloadData]; 
});