dispatch_queue

dispatch_group_notify方法调用执行时，如果没有添加到group的任务在执行，那么直接执行notify的Block，如果有则等待现有的任务执行完之后执行notify的Block

- (void)test_1 {
    dispatch_group_t group = dispatch_group_create();
    dispatch_queue_t queue = dispatch_queue_create("test_for_group_events", DISPATCH_QUEUE_CONCURRENT);
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        NSLog(@"=========> finsh running 00");
    });
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        NSLog(@"=========> finsh running 01");
    });
    dispatch_group_async(group, queue, ^{
        [NSThread sleepForTimeInterval:1.0];
        NSLog(@"============> 1");
    });
    dispatch_group_enter(group);
    dispatch_async(queue, ^{
        [NSThread sleepForTimeInterval:0.6];
        NSLog(@"============> 2");
        dispatch_group_leave(group);
    });
    dispatch_group_notify(group, queue, ^{
        NSLog(@"=========> finsh running 02");
    });
    dispatch_group_enter(group);
    dispatch_async(dispatch_get_main_queue(), ^{
        [NSThread sleepForTimeInterval:0.3];
        NSLog(@"============> 3");
        dispatch_group_leave(group);
    });
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        NSLog(@"=========> finsh running 03");
    });
    dispatch_group_notify(group, dispatch_get_main_queue(), ^{
        NSLog(@"=========> finsh running 04");
    });
}

给dispatch_queue增加属性

dispatch_queue_set_specific(_queue, kDispatchQueueSpecificKey, (__bridge void *)self, NULL);

dispatch_sync(dispatch_get_global_queue(0, 0), ^{
        NSLog(@"是否在主线程执行：%d",[NSThread isMainThread]);
        NSLog(@"%@",[NSOperationQueue currentQueue]);
    });

在主线程调用同步，输出为是主线程、为主队列