iOSマルチスレッド開発シリーズの(3)Grand Central Dispatch(GCD)

dispatch_queue_t  dispatch_queue_create(const char *label,  dispatch_queue_attr_t attr);  

    dispatch_queue_t queue = dispatch_get_main_queue()；       （  ）

dispatch_queue_t  dispatch_queue_create(const char *label,  dispatch_queue_attr_t attr);  

                DISPATCH_QUEUE_CONCURRENT

dispatch_queue_t queue=dispatch_get_global_queue(long identifier, unsigned long flags)； 

#define DISPATCH_QUEUE_PRIORITY_HIGH 2 
#define DISPATCH_QUEUE_PRIORITY_DEFAULT 0
#define DISPATCH_QUEUE_PRIORITY_LOW (-2)
#define DISPATCH_QUEUE_PRIORITY_BACKGROUND INT16_MIN

dispatch_sync(queue, ^{
    //block    
}); 

dispatch_async(queue, ^{
    //block    
});  

static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
// code to be executed once
});

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

　　//            

　　dispatch_sync(dispatch_get_main_queue(), ^{
    //       UI  

　　});
});

double delayInSeconds = N;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
// code to be executed on the main queue after delay
}); 

    dispatch_async(dispatch_get_global_queue(0, 0), ^{
    });

    dispatch_barrier_async(dispatch_queue_t queue, ^{

}); 

   dispatch_group_t group = dispatch_group_create();
dispatch_group_async(group, dispatch_get_global_queue(0,0), ^{
 //       
});
dispatch_group_async(group, dispatch_get_global_queue(0,0), ^{
   //       
});
dispatch_group_notify(group, dispatch_get_global_queue(0,0), ^{
 //     
});