I want to share something about my misunderstanding about typeof.

The story goes from my pull request to mopub repo. I found following code occurs in a block. It seems not using weakSelf for weak-strong dance, but capturing self by the __typeof__(self).

__strong __typeof__(self) strongSelf = weakSelf;

So I create a pull request and change it to

__strong __typeof__(weakSelf) strongSelf = weakSelf;

In fact, my PR had a mistake. The typeof, __typeof and __typeof__ are compile-time flag. Thus self in this block is not retained.

Another thing is that, __typeof__(weakSelf) is not a good pattern. This will carry __weak attribute, thus we need an explicit __strong attribute to overwrite it. Thus using __typeof__(self) is better, to prevent accidentally creating a strongSelf which is actually not.