iOS gcd some ways to use

1- (void) gcdmethed{2     //Background Execution3Dispatch_async (Dispatch_get_global_queue (Dispatch_queue_priority_high,0), ^{4         5         //actions performed in the background6NSLog (@"Background Operation");7     });8     9     //Main thread ExecutionTenDispatch_async (Dispatch_get_main_queue (), ^{ One         A         //operations performed by the main thread -NSLog (@"Main thread Operation"); -     }); the      -      -     //Disposable Execution -      for(intI=0; i<2; i++) { +         Staticdispatch_once_t Oncetoken; -Dispatch_once (&oncetoken, ^{ +             //code executes once ANSLog (@"code executes once"); at         }); -     } -      - //2 seconds delay execution -     DoubleDelayinseconds =2.0; -dispatch_time_t poptime = Dispatch_time (Dispatch_time_now, (int64_t) (Delayinseconds *nsec_per_sec)); inDispatch_after (Poptime, Dispatch_get_main_queue (), ^ (void){ -NSLog (@"delayed 2 seconds of execution"); to     }); +      -     //Custom dispatch_queue_t thedispatch_queue_t Urls_queue = Dispatch_queue_create ("blog.devtang.com", NULL); *dispatch_queue_t urls_queue2 = Dispatch_queue_create ("TEST", dispatch_queue_concurrent);//Parallel Queue dispatch_queue_serial Walkthrough Queue $Dispatch_async (Urls_queue, ^{Panax Notoginseng          -     }); the //dispatch_release (Urls_queue); ARC does not need +      A      the     //Merge Summary Results +      -dispatch_group_t Group =dispatch_group_create (); $Dispatch_group_async (Group, Dispatch_get_global_queue (0,0), ^{ $             //thread one in parallel execution -     }); -Dispatch_group_async (Group, Dispatch_get_global_queue (0,0), ^{ the             //threads executed in parallel two -     });WuyiDispatch_group_notify (Group, Dispatch_get_global_queue (0,0), ^{ the             //Summary Results -     }); Wu      -Dispatch_async (Dispatch_get_global_queue (Dispatch_queue_priority_default,0), ^{ About         $Dispatch_async (Dispatch_get_main_queue (), ^{ -              -         }); -     }); A      +}

iOS gcd some ways to use