Objectivec iOS 块和对自身的强弱引用

我有一个关于iOS中块中self的强引用和弱引用的问题.我知道在块内引用self的正确方法是在块外创建一个弱引用，然后在块内创建一个弱引用的强引用，如下所示:

__weak typeof(self) weakSelf = self;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^ {
    typeof(self) strongSelf = weakSelf;
    NSLog(@"%@", strongSelf.someProperty);
});

但是，如果有嵌套块，会发生什么？一套参考资料够了吗？还是每个街区都需要一套新的？例如，以下哪项是正确的？

这是:

__weak typeof(self) weakSelf = self;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^ {
    typeof(self) strongSelf = weakSelf;
    NSLog(@"%@", strongSelf.someProperty);
    dispatch_async(dispatch_get_main_queue(), ^ {
        strongSelf.view.frame = CGRectZero;
    });
});

或者这个:

__weak typeof(self) weakSelf = self;
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^ {
        typeof(self) strongSelf = weakSelf;
        NSLog(@"%@", strongSelf.someProperty);
        __weak typeof(strongSelf) weakSelf1 = strongSelf;
        dispatch_async(dispatch_get_main_queue(), ^ {
            typeof(strongSelf) strongSelf1 = weakSelf1;
            strongSelf1.view.frame = CGRectZero;
        });
    });

任何信息或解释都将不胜感激！