Adopting walkarounds for UICollectionView

[Timur Yusipov]

The original implementation of the diffing algorythm has some walkarounds to respect UICollectionView's internal behaviour and prevent UICollectionView from throwing exceptions in performBatchUpdates function:

https://github.com/Instagram/IGListKit/blob/master/Source/Common/IGListIndexPathResult.m#L41
https://github.com/Instagram/IGListKit/blob/master/Source/Common/IGListIndexSetResult.m#L43

Without those walkarounds I receive lots of

attempt to perform a delete and a move from the same index path (<NSIndexPath: 0xc00000000ce00016> {length = 2, path = 0 - 103})

in a stress test with a collection of 1000 elements being under repeated random inserts, deletes, moves and updates repeated

So, I wonder, were there any reasons for loosing that functionality in this port?

[Stan Chang Khin Boon]

Hey! It’s very likely that the port was based on an older version of the algorithm.

I’ll have to re-review the 2 codebase to see if I miss out anything.

Originally, this is a 1-1 reference implementation of the IGListKit and I intend to keep it that way though. Do you have any idea what part of the code is missing?

[Stan Chang Khin Boon]

If you can share with me a stress testing code I can try to spend some time on this over the weekend!

[Timur Yusipov]

Thanks for such a fast reply!

I linked to the missing parts in the original message. These are the functions called resultForBatchUpdates
I will try to share the test or the missing code for a batch updates soon

[Timur Yusipov]

I also see, that original diffing algorythm supports index paths diff in complement with index diff, while the ported algorythm supports only index diff
Again, see the links in the original message

[Stan Chang Khin Boon]

#7 and #8 are now merged.

This is great!

Is there a way you could provide useful guide on the readme on how to use this on collection view? (or table view)

[Timur Yusipov]

Just use

let diff = List.diffing(
     oldArray: from,
     newArray: to
).forBatchUpdates()

instead of

let diff = List.diffing(
     oldArray: from,
     newArray: to
)

Note .forBatchUpdates() in the end.
Sorry, I do not have time for pull requests at the moment.