GCD-group、notify、wait

最新推荐文章于 2024-09-14 08:31:55 发布

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最新推荐文章于 2024-09-14 08:31:55 发布

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分类专栏： GCD

本文链接：https://blog.youkuaiyun.com/lcx_love_yx/article/details/89004199

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本文通过两个实例深入解析了GCD (Grand Central Dispatch) 中dispatch_group_notify和dispatch_group_wait的功能与用法。第一个例子展示了如何使用dispatch_group_notify实现任务完成后的回调通知。第二个例子则演示了dispatch_group_wait如何让后续代码等待所有分组任务完成后继续执行。

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1 dispatch_group_notify，dispatch_group_async执行完后再执行notify；

2 dispatch_group_wait后代码等group执行完，再执行；

例1 dispatch_group_notify

- (void)groupAsyncSummit_notify{
dispatch_group_t group = dispatch_group_create();

    dispatch_group_async(group, _mainQueue, ^{
        [self doSometing:@"1"];
        });
    dispatch_group_async(group, _mainQueue, ^{
        [self doSometing:@"2"];
    });

    dispatch_group_notify(group, _globalQueue, ^{
        [self doSometing:@"notify"];
    });

    dispatch_group_async(group, _globalQueue, ^{
        [self doSometing:@"3"];
        [self doSometing:@"3-1"];

});
[self doSometing:@"4"];
}

输出：43并发，再3-1、1并发，再执行2，最后执行notify；

说明：

dispatch_group_async搭_globalQueue，异步并发执行；

dispatch_group_async搭 _mainQueue，异步串行，加在_mainQueue队列的最后；

例2 dispatch_group_wait，

- (void)groupAsyncSummit_wait{
    dispatch_group_t group = dispatch_group_create();

    dispatch_group_async(group, _globalQueue, ^{
        [self doSometing:@"1"];
    });
    dispatch_group_async(group, _globalQueue, ^{
        [self doSometing:@"2"];
    });
    dispatch_group_async(group, _globalQueue, ^{
        [self doSometing:@"3"];
    });

    dispatch_group_wait(group, DISPATCH_TIME_FOREVER);

    [self doSometing:@"4"];
}