Apple GCD问题

九变形战士

已于 2025-02-14 13:44:11 修改

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文章标签： ios

于 2023-04-06 23:52:52 首次发布

本文链接：https://blog.youkuaiyun.com/callauxiliary/article/details/130001612

1.在主线程执行下面代码的输出顺序是：
主队列异步执行:

	NSLog(@"1");
    dispatch_async(dispatch_get_main_queue(), ^{
        NSLog(@"2");
    });
    NSLog(@"3");

—Output：132—
主队列同步执行:

	NSLog(@"1");
    dispatch_sync(dispatch_get_main_queue(), ^{
        NSLog(@"2");
    });
    NSLog(@"3");

—Output：主线程执行异步任务造成死锁，程序挂了—
全局队列异步执行：

	NSLog(@"1");
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        NSLog(@"2");
    });
    NSLog(@"3");

—Output：132—
全局队列同步执行：

	NSLog(@"1");
    dispatch_sync(dispatch_get_global_queue(0, 0), ^{
        NSLog(@"2");
    });
    NSLog(@"3");

—Output：123—

	NSLog(@"1");
    dispatch_queue_t queue = dispatch_queue_create("com.queue.serial", DISPATCH_QUEUE_SERIAL);
    dispatch_async(queue, ^{
        NSLog(@"2");
    });
    NSLog(@"3");

—Output：132—

	NSLog(@"1");
    dispatch_queue_t queue = dispatch_queue_create("com.queue.serial", DISPATCH_QUEUE_SERIAL);
    dispatch_sync(queue, ^{
        NSLog(@"2");
    });
    NSLog(@"3");

—Output：123—

	dispatch_queue_t queue = dispatch_queue_create("com.queue.serial", 		DISPATCH_QUEUE_SERIAL);
    NSLog(@"1");
    dispatch_async(queue, ^{
        NSLog(@"2");
        dispatch_async(queue, ^{
            NSLog(@"3");
        });
    });
    NSLog(@"4");

—Output：1423—

	dispatch_queue_t queue = dispatch_queue_create("com.queue.serial", DISPATCH_QUEUE_SERIAL);
    NSLog(@"1");
    dispatch_sync(queue, ^{
        NSLog(@"2");
        dispatch_async(queue, ^{
            NSLog(@"3");
        });
    });
    NSLog(@"4");

—Output：1243—

	dispatch_queue_t queue = dispatch_queue_create("com.queue.serial", DISPATCH_QUEUE_SERIAL);
    NSLog(@"1");
    dispatch_sync(queue, ^{
        NSLog(@"2");
        dispatch_sync(queue, ^{
            NSLog(@"3");
        });
    });
    NSLog(@"4");

—Output：程序挂了—

	dispatch_queue_t queue = dispatch_queue_create("com.queue.serial", DISPATCH_QUEUE_CONCURRENT);
    NSLog(@"1");
    dispatch_sync(queue, ^{
        NSLog(@"2");
        dispatch_sync(queue, ^{
            NSLog(@"3");
        });
    });
    NSLog(@"4");

—Output：1234—

	dispatch_queue_t queue = dispatch_queue_create("com.queue.serial", DISPATCH_QUEUE_CONCURRENT);
    NSLog(@"1");
    dispatch_async(queue, ^{
        NSLog(@"2");
        dispatch_async(queue, ^{
            NSLog(@"3");
        });
    });
    NSLog(@"4");

—Output：1423—

	dispatch_queue_t queue = dispatch_queue_create("com.queue.serial", DISPATCH_QUEUE_CONCURRENT);
    NSLog(@"1");
    dispatch_async(queue, ^{
        NSLog(@"2");
        dispatch_sync(queue, ^{
            NSLog(@"3");
        });
    });
    NSLog(@"4");

—Output：1423—

	dispatch_queue_t queue = dispatch_queue_create("com.queue.serial", DISPATCH_QUEUE_CONCURRENT);
    NSLog(@"1");
    dispatch_sync(queue, ^{
        NSLog(@"2");
        dispatch_async(queue, ^{
            NSLog(@"3");
        });
    });
    NSLog(@"4");

—Output：1243—

	dispatch_queue_t serial = dispatch_queue_create("com.queue.serial", DISPATCH_QUEUE_SERIAL);
    NSLog(@"1");
    dispatch_queue_t concurrent = dispatch_queue_create("com.queue.concurrent", DISPATCH_QUEUE_CONCURRENT);
    dispatch_async(serial, ^{
        NSLog(@"2");
        dispatch_sync(concurrent, ^{
            NSLog(@"3");
        });
        NSLog(@"4");
    });
    NSLog(@"5");