ios - 嵌套的 dispatch_async(dispatch_async 在另一个 dispatch_async 中)

Question

我如何在 dispatch_async 中正确调用 dispatch_async 调用

dispatch_group_t downloadQueue = dispatch_group_create();
dispatch_group_async(downloadQueue,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {

NSLog(@"Main");
[NSThread sleepForTimeInterval:5.0];
NSLog(@"End");

    [self myMethod];

});
dispatch_group_notify(downloadQueue,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,0), ^ {

    NSLog(@"FINAL");

});

这是我的方法:

-(void)myMethod
{
    dispatch_group_t group = dispatch_group_create();
    dispatch_group_async(group,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
        // block1
        NSLog(@"Block1");
        [NSThread sleepForTimeInterval:5.0];
        NSLog(@"Block1 End");
    });
    dispatch_group_async(group,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
        // block2
        NSLog(@"Block2");
        [NSThread sleepForTimeInterval:8.0];
        NSLog(@"Block2 End");
    });

    dispatch_group_notify(group,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
        // block3
        NSLog(@"Block3");
    });
}

我的输出是:
主要
结束
block 1
Block2
决赛
Block1结束
Block2结束
Block3

但我需要
主要
结束
block 1
Block2
Block1结束
Block2结束
Block3
最后的

Answer 1

您只需要收到您的 myMethod 组的通知。您的代码将是:

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {

    NSLog(@"Main");
    [NSThread sleepForTimeInterval:5.0];
    NSLog(@"End");

    dispatch_group_notify([self myMethod],dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,0), ^ {

        NSLog(@"FINAL");

    });
});

-(dispatch_group_t)myMethod{

    dispatch_group_t group = dispatch_group_create();

    dispatch_group_async(group,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
        // block1
        NSLog(@"Block1");
        [NSThread sleepForTimeInterval:5.0];
        NSLog(@"Block1 End");
    });


    dispatch_group_async(group,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
        // block2
        NSLog(@"Block2");
        [NSThread sleepForTimeInterval:8.0];
        NSLog(@"Block2 End");
    });

    dispatch_group_notify(group,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
        // block3
        NSLog(@"Block3");
    });
    return group;
}