implementation discussion: why to use dispatch_group_async along with dispatch_group_enter/leave?

[Josscii]

I dug into the source, and found that you use dispatch_group_async along with dispatch_group_enter/leave, is this the right way to use GCD group?

I googled it and find an blog explaining the concept: Using dispatch groups to wait for multiple web services, it says use either dispatch_group_async OR dispatch_group_enter/leave.

Anyone can explain it?

If it is not appropriate to ask there, sorry for that, I will close it.

[shoumikhin]

Thank you for digging into the code, Josscii!
We're always happy to clarify any non-trivial aspects.

The docs mention that dispatch_group_async is just a convenience wrapper for dispatch_group_enter/leave, so the two are not mutually exclusive.

We use dispatch groups primarily to facilitate testing with FBLWaitForPromisesWithTimeout.

Hope that helps.

[Josscii]

Thanks for your information.

It seems that I didn't understand your intention to use dipatch_group, sorry for the stupid question.

Now it becomes more clear, I will read your code and learn more from it.