Iglistkit: IGListGridCollectionViewLayout crashes when setting MinimumInteritemSpacing

[MarvinNazari]

minimumInteritemSpacing on IGListGridCollectionViewLayout dosent work properly, if the section width is equal to collectionview width (full width), and the minimumInteritemSpacing is > 0, it crashes.
an example layout can be like Instagram explore page, the video section is full width, and the grid has minimumInteritemSpacing = 1

cc @zhubofei

[zhubofei]

@MarvinNazari This is weird, I just wrote a test for full-width items with non-zero interitem spacing set up and it works. Could you check if your item width exceeds the collectionView width first()? If the problem still exists, would you mind posting a sample project so that I can dig into it?

[zhubofei]

And we should definitely add a check in here. If item width exceeds collectionView width we should throw an error. 🤔

[MarvinNazari]

@zhubofei yeah not getting the crash on the sample code, but definitly still something wrong, here can u still see that layout is not how it supposed to be. try to comment out this part so the cells appears again

[MarvinNazari]

@zhubofei ah found the crash, it happens when performing an update, so look at my latest commit at the sample code, and press "Add more" on navbar.

2016-12-23 00:41:36.602 IGListKitIssue[49325:3478853] *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 3 beyond bounds [0 .. 2]'
*** First throw call stack:
(
    0   CoreFoundation                      0x000000011287dd4b __exceptionPreprocess + 171
    1   libobjc.A.dylib                     0x000000011012921e objc_exception_throw + 48
    2   CoreFoundation                      0x00000001127af2eb -[__NSArrayM objectAtIndex:] + 203
    3   IGListKit                           0x000000010fb869a4 -[_IGListGridLayoutLine attributesForItemAtIndexPath:withXOffset:] + 196
    4   IGListKit                           0x000000010fb86494 -[_IGListGridLayoutLine attributesForItemAtIndexPath:] + 820
    5   IGListKit                           0x000000010fb84224 -[IGListGridCollectionViewLayout layoutAttributesForItemAtIndexPath:] + 388
    6   UIKit                               0x0000000110f9cfa7 -[UICollectionViewData layoutAttributesForItemAtIndexPath:] + 341
    7   UIKit                               0x0000000110f9d160 -[UICollectionViewData layoutAttributesForGlobalItemIndex:] + 57
    8   UIKit                               0x0000000110f53206 -[UICollectionView _viewAnimationsForCurrentUpdate] + 6084
    9   UIKit                               0x0000000110f58899 __71-[UICollectionView _updateWithItems:tentativelyForReordering:animator:]_block_invoke.1993 + 197
    10  UIKit                               0x00000001106b2239 +[UIView(Animation) performWithoutAnimation:] + 90
    11  UIKit                               0x0000000110f573ef -[UICollectionView _updateWithItems:tentativelyForReordering:animator:] + 3942
    12  UIKit                               0x0000000110f51421 -[UICollectionView _endItemAnimationsWithInvalidationContext:tentativelyForReordering:animator:] + 17765
    13  UIKit                               0x0000000110f59e72 -[UICollectionView _endUpdatesWithInvalidationContext:tentativelyForReordering:animator:] + 71
    14  UIKit                               0x0000000110f5a1b4 -[UICollectionView _performBatchUpdates:completion:invalidationContext:tentativelyForReordering:animator:] + 432
    15  UIKit                               0x0000000110f59fe1 -[UICollectionView _performBatchUpdates:completion:invalidationContext:tentativelyForReordering:] + 91
    16  UIKit                               0x0000000110f59f63 -[UICollectionView _performBatchUpdates:completion:invalidationContext:] + 74
    17  UIKit                               0x0000000110f59eb8 -[UICollectionView performBatchUpdates:completion:] + 53
    18  IGListKit                           0x000000010fb6919c -[IGListAdapterUpdater performBatchUpdatesWithCollectionView:] + 2956
    19  IGListKit                           0x000000010fb6bf15 __54-[IGListAdapterUpdater queueUpdateWithCollectionView:]_block_invoke + 357
    20  libdispatch.dylib                   0x00000001134a5978 _dispatch_call_block_and_release + 12
    21  libdispatch.dylib                   0x00000001134cf0cd _dispatch_client_callout + 8
    22  libdispatch.dylib                   0x00000001134af8a4 _dispatch_main_queue_callback_4CF + 406
    23  CoreFoundation                      0x0000000112841e49 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
    24  CoreFoundation                      0x000000011280737d __CFRunLoopRun + 2205
    25  CoreFoundation                      0x0000000112806884 CFRunLoopRunSpecific + 420
    26  GraphicsServices                    0x00000001146f5a6f GSEventRunModal + 161
    27  UIKit                               0x00000001105f8c68 UIApplicationMain + 159
    28  IGListKitIssue                      0x000000010fa9bc2f main + 111
    29  libdyld.dylib                       0x000000011351b68d start + 1
    30  ???                                 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

[zhubofei]

@MarvinNazari I think I just caught the :bug:. I will post a PR tomorrow.

[MarvinNazari]

@zhubofei just tested #361, and works pefectly! ❤️