Fix collection view data inconsistency

[Adlai-Holler]

This resolves #654

We could remove the flag and just call [self layoutIfNeeded] immediately after [super reloadData]

• + Reduces complexity of ASCollectionView
• - Relies on implementation details of UICollectionView
• - Performance cost

[Adlai-Holler]

Should we call completion(YES) if we suppressed the update due to a pending reload?

[eanagel]

@adly-holler, this is some great detective work! The idea of simply calling layoutIfNeeded after our reloadData is very attractive indeed. (Would that actually drop this down to a 1-line commit?) You mention performance cost as a drawback to this approach, could you expand on that a bit?

[eanagel]

Oh yes and another question, is this a potential problem for ASTableView as well? Have you explored that side of the equation?

[Adlai-Holler]

@eanagel Thanks! It would indeed make this a 1-line commit, assuming that reloadData -> setNeedsLayout which I'd bet it does. The performance cost comes from laying out the cells when they don't necessarily need to be laid out. For a simple example, consider if you called reloadData 5 times during the same frame. The collection view cells would get laid out 5 times for one frame.

As for ASTableView, I don't think it behaves the same way but I'll check it tomorrow and post back on this thread either way.

[appleguy]

Will analyze more, merging as it does fix the test project submitted recently.

[Adlai-Holler]

Note: Ported the sample project to table view and I'm not seeing the same issue.