The principle of multi-threaded CGD dispatching group

Our common GCD scheduling group approach

1 //gcd Common Dispatching group2-(void) demo1{3     4     //create dispatch groups and queues5dispatch_group_t Group =dispatch_group_create ();6dispatch_queue_t queue = Dispatch_queue_create ("Changyong", dispatch_queue_concurrent);7     8     //to add a task to a dispatch group9Dispatch_group_async (group, queue, ^{TenNSLog (@"time-consuming operation _11111111"); One     }); ADispatch_group_async (group, queue, ^{ -         //simulate time-consuming operations -[Nsthread Sleepfortimeinterval:2]; theNSLog (@"time-consuming operation _22222222"); -     }); -Dispatch_group_async (group, queue, ^{ -NSLog (@"time-consuming operation _33333333"); +     }); -      +     //tasks performed after all tasks have been completed ADispatch_group_notify (Group, Dispatch_get_main_queue (), ^{ atNSLog (@"All tasks complete, update UI actions"); -     }); -}

GCD Scheduling Group principle

1 //principle and method of GCD dispatching group2-(void) demo2{3     4     //create dispatch groups and queues5dispatch_group_t Group =dispatch_group_create ();6dispatch_queue_t queue = Dispatch_queue_create ("Yuanli", dispatch_queue_concurrent);7     8     //Task 19 Dispatch_group_enter (group);TenDispatch_async (Queue, ^{ OneNSLog (@"Task 1"); A Dispatch_group_leave (group); -     }); -      the     //Task 2 - Dispatch_group_enter (group); -Dispatch_async (Queue, ^{ -[Nsthread Sleepfortimeinterval:2]; +NSLog (@"Task 2"); - Dispatch_group_leave (group); +     }); A      at     //Task 3 - Dispatch_group_enter (group); -Dispatch_async (Queue, ^{ -NSLog (@"Task 3"); - Dispatch_group_leave (group); -     }); in      -     //All Tasks completed toDispatch_group_notify (Group, Dispatch_get_main_queue (), ^{ +         -NSLog (@"The task finishes, refreshes the UI"); the     }); *      $     //wait for the above code to execute after executing the following code, Parameter 2: Wait Time outPanax Notoginseng     //dispatch_group_wait (Group, dispatch_time_forever); -      theNSLog (@"Hello"); +}

The principle of multi-threaded CGD dispatching group