GCD

- (void)viewDidLoad {
    [super viewDidLoad];
//    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
//        NSLog(@"%@", [NSThread currentThread]);
//    });
//   
//    dispatch_apply(4, DISPATCH_QUEUE_PRIORITY_DEFAULT, ^(size_t index) {
//        NSLog(@"%zu", index);
//    });
    // Do any additional setup after loading the view, typically from a nib.
   
    //GCD异步线程的创建
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
       
    });
 
    //GCD 重复执行线程
    dispatch_apply(4, DISPATCH_QUEUE_PRIORITY_DEFAULT, ^(size_t index) {
       
    });
  
    //GCD 创建串行队列
   
    dispatch_queue_t queue = dispatch_queue_create("com.changtu.be", DISPATCH_QUEUE_CONCURRENT);
   
    //线程ABC 一次执行.因为它是一个串行队列
    dispatch_async(queue, ^{
        [NSThread sleepForTimeInterval:1];
    });
    dispatch_barrier_async(queue, ^{
        [NSThread sleepForTimeInterval:3];
    });
    dispatch_async(queue, ^{
       
    });
   
//    GCD群组通知等所有线程都完成工作后.在做通知
    dispatch_group_t group = dispatch_group_create();
    //线程AB
    dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [NSThread sleepForTimeInterval:2];
    });
    dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
       
    });
   
    //待群组里的线程都完成之后调用的通知
    dispatch_group_notify(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
       
    });
    //GCD 实现计时器
    __block int time = 30;
    CGFloat reSecond = 1.0;
    dispatch_queue_t queueTime = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queueTime);
    dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, reSecond * NSEC_PER_SEC, 0);
    dispatch_source_set_event_handler(timer, ^{
        time--;
        NSLog(@"%d", time);
        if (time == 0) {
            dispatch_source_cancel(timer);
        }
    });
    dispatch_resume(timer);
//    GCD线程间通信－调用主线程修改UI：
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        NSLog(@"异步数据处理 - %@", [NSThread currentThread]);
        [NSThread sleepForTimeInterval:2];
        NSLog(@"数据处理完成");
       
        // 调用主线程更新UI
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"更新UI - %@", [NSThread currentThread]);
//            [self editUINow];
        });
    });
    // 获取主线程
    dispatch_get_main_queue();
   
    // 创建队列：第一个参数是队列的名称，它会出现在调试程序等之中，是个内部名称。第二个参数代表它是串行队列还是并并发队列，NULL代表串行队列。
    dispatch_queue_t dispatch_queue_create(const char *label, dispatch_queue_attr_t attr);
   
    // 创建异步调度队列
    void dispatch_async(dispatch_queue_t queue, dispatch_block_t block);
   
    // 恢复队列
    void dispatch_resume(dispatch_object_t object);
   
    // 暂停队列
    void dispatch_suspend(dispatch_object_t object);
 
   

}