iOSにおけるマルチスレッドのGCD応用

 GCD Grand Central Dispatch ， 。 ：  

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

    dispatch_async(dispatch_get_main_queue(), ^{
        // 
    });

static dispatch_once_t once;
    dispatch_once(&once, ^{
       // 
    });

float delaySeconds = 3.0f;
    dispatch_time_t disTime = dispatch_time(DISPATCH_TIME_NOW, delaySeconds * NSEC_PER_SEC);
    dispatch_after(disTime, dispatch_get_main_queue(), ^{
        // 
    });

    dispatch_queue_t serialQueue = dispatch_queue_create("queueName", DISPATCH_QUEUE_SERIAL);
    dispatch_async(serialQueue, ^{
        //code  
        NSLog(@" ： ");
    });
    
    dispatch_async(serialQueue, ^{
        //code  
        NSLog(@" ： ");
    });

    dispatch_queue_t concurrentQueue = dispatch_queue_create("queueName", DISPATCH_QUEUE_CONCURRENT);
    dispatch_async(concurrentQueue, ^{
        //code  
        NSLog(@" ： ");
    });
    
    dispatch_async(concurrentQueue, ^{
        //code  
        NSLog(@" ： ");
    });

    dispatch_group_t group = dispatch_group_create();
    dispatch_group_async(group, dispatch_get_global_queue(0, 0), ^{
        // 
        NSLog(@"notify: ");
    });
    dispatch_group_async(group, dispatch_get_global_queue(0, 0), ^{
        // 
        NSLog(@"notify: ");
    });
    // group 
    dispatch_group_notify(group, dispatch_get_global_queue(0, 0), ^{
        // 
        NSLog(@"notify: ");
    });
    dispatch_group_async(group, dispatch_get_global_queue(0, 0), ^{
        // 
        NSLog(@"notify: ");
    });

    dispatch_queue_t conCurrentQueue = dispatch_queue_create("conCurrentQueue", DISPATCH_QUEUE_CONCURRENT);
    dispatch_async(conCurrentQueue, ^{
        // 
        NSLog(@"barrier: ");
    });
    dispatch_async(conCurrentQueue, ^{
        // 
        NSLog(@"barrier: ");
    });
    dispatch_barrier_async(conCurrentQueue, ^{
        // 
        NSLog(@"barrier: ");
    });
    dispatch_async(conCurrentQueue, ^{
        // 
        NSLog(@"barrier: ");
    });
    dispatch_async(conCurrentQueue, ^{
        // 
        NSLog(@"barrier: ");
    });