cellForItemAtIndexPath: firing in iOS7 but not iOS6 - ios

Question

When recently adding a UICollectionView with a custom UICollectionViewFlowLayout subclass, the collectionView:cellForItemAtIndexPath: method is only being called on iOS7, and not on iOS6. In other words, everything works great in iOS7 but my custom collectionView items are not showing up in iOS6. Interestingly, the cells appear to be there (the collectionView scrolls), but all items are empty with a white background.
The collectionView was set up in a .xib file, dataSource and delegate were attached, and UICollectionViewDataSource and UICollectionViewDelegateFlowLayout were added after the #interface call in the view controller .h file.
The collectionView item size, section inset, line spacing, and inter-item spacing are all being set in the custom flow layout init method.
Some code:
- (void)viewDidLoad
{
[super viewDidLoad];
self.collectionView.collectionViewLayout = [[TFSpringFlowLayout alloc] init];
[self.collectionView registerClass:[TFWorkoutCell class] forCellWithReuseIdentifier:CellIdentifier];
}
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section
{
// This method is returning a value > 0
return _workouts.count;
}
- (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView
{
return 1;
}
-(UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
// This is being called on iOS7, but is never being called on iOS6
...removed for clarity
return cell;
}
EDIT: Issue Solved. My custom Flow Layout included some iOS7-specific overrides utilizing the new UIDynamicAnimator class. These were not causing a crash, but were preventing the cells from being drawn in iOS6.

Answer 1

Here is what the issue was for me, in case anybody else runs into this problem in the future.
My custom UICollectionViewFlowLayout contained several method overrides to implement iOS7's new UIKit Dynamics. These did not cause the application to crash, but prevented the cells from being drawn in iOS6.
Here is the offending code:
-(NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
return [self.dynamicAnimator itemsInRect:rect];
}
-(UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath {
return [self.dynamicAnimator layoutAttributesForCellAtIndexPath:indexPath];
}
And the simple change required for the fix:
-(NSArray *)layoutAttributesForElementsInRect:(CGRect)rect {
if ([UIDynamicAnimator class])
return [self.dynamicAnimator itemsInRect:rect];
else
return [super layoutAttributesForElementsInRect:rect];
}
-(UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath {
if ([UIDynamicAnimator class])
return [self.dynamicAnimator layoutAttributesForCellAtIndexPath:indexPath];
else
return [super layoutAttributesForItemAtIndexPath:indexPath];
}
Adding an if/else statement to check for iOS6 or iOS7 and only returning the appropriate response fixed the issue for me. Hope this helps someone else!