Open Radar

 
Summary:
A UICollectionView with a UICollectionViewFlowLayout should allow autolayout to allow for self-sizing cells. This works for static layouts, but when items are inserted or removed the cells resize to the estimated size before expanding again.

Steps to Reproduce:
See sample project attached.

Create a UICollectionView whose cells use autolayout to describe their size. Enable self-sizing cells by setting an estimatedItemSize on the UICollectionViewFlowLayout, e.g. layout.estimatedItemSize = CGSizeMake(10.0, 10.0);

Insert items into the UICollectionView, e.g.

[self.collectionView performBatchUpdates:^{
    [self.collectionView insertItemsAtIndexPaths:@[indexPath]];
} completion:nil];

Expected Results:
When inserting/removing items, the cells maintain their size.

Actual Results:
Cells reset to their estimated size before expanding to their actual size.

Note: if the estimatedItemSize is larger than the actual size, the app will crash. That's for another radar.

Version:
iOS 9.1

Notes:
Broken since iOS 8.0