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POCollectionView + UIKit Dynamics crashing on performBatchUpdates:
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  1. POCollectionView + UIKit Dynamics crashing on performBatchUpdates:
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    copied!<p>I'm stucked with a strange crash and trying to fix it all day long. I have a custom UICollectionViewLayout that basically adds gravity and collision behavious to the cells.</p> <p>The implementation works great! The problem happens when I try to delete one cell using: [self.collectionView performBatchUpdates:].</p> <p>It gives me the following error:</p> <pre><code>2013-12-12 21:15:35.269 APPNAME[97890:70b] *** Assertion failure in -[UICollectionViewData validateLayoutInRect:], /SourceCache/UIKit_Sim/UIKit-2935.58/UICollectionViewData.m:357 2013-12-12 20:55:49.739 APPNAME[97438:70b] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'UICollectionView recieved layout attributes for a cell with an index path that does not exist: &lt;NSIndexPath: 0x975d290&gt; {length = 2, path = 0 - 4}' </code></pre> <p><strong>My model is being handled correctly and I can see it removing the item from it!</strong></p> <p>The indexPaths of the item to delete is being passed correctly between objects. The only time the collectionView update doen't crash is when I delete the last cell on it, otherwise, the crash happens.</p> <p>Here's the code I'm using to delete the cell.</p> <pre><code>- (void)removeItemAtIndexPath:(NSIndexPath *)itemToRemove completion:(void (^)(void))completion { UICollectionViewLayoutAttributes *attributes = [self.dynamicAnimator layoutAttributesForCellAtIndexPath:itemToRemove]; [self.gravityBehaviour removeItem:attributes]; [self.itemBehaviour removeItem:attributes]; [self.collisionBehaviour removeItem:attributes]; [self.collectionView performBatchUpdates:^{ [self.fetchedBeacons removeObjectAtIndex:itemToRemove.row]; [self.collectionView deleteItemsAtIndexPaths:@[itemToRemove]]; } completion:nil]; } </code></pre> <p>The CollectionView delegates that handles the cell attibutes are the basic ones below.</p> <pre><code>- (CGSize)collectionViewContentSize { return self.collectionView.bounds.size; } - (NSArray *)layoutAttributesForElementsInRect:(CGRect)rect { return [self.dynamicAnimator itemsInRect:rect]; } - (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath { return [self.dynamicAnimator layoutAttributesForCellAtIndexPath:indexPath]; } </code></pre> <p>Things I already tried with no success: - Invalidating the layout - Reloading the data - Removing the behaviours from the UIDynamicAnimator and adding them again after the update</p> <p>Any insights?</p> <p>A source code with the problem is available on this repository. Please check it out. <a href="https://github.com/ghvillasboas/CollectionViewDynamics" rel="noreferrer">Code Repository</a></p> <p>Best. George.</p>
 

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