Our DNA is written in Swift

Bug: NSCollectionView Move Sections Crash

We are so foolhardy that we are using NSCollectionView in an internal project that gets widely used by an enterprise client of ours. We found this latest crashing bug while updating the application for macOS 10.12 wich is where the issue first appeared.

The only workaround at this time is to remove animation via animator() and replace it with a reloadData. Thus we vote NSCollectionView for worst Apple API on macOS.

This bug is filed as rdar://28337446 and on Open Radar.


When you move 1 section to another section NSCollectionView crashes on animation (for example 0 to 1)

Steps to Reproduce

  1. Run sample
  2. Press Move Section 0 down
  3. Crash on animation

Expected Results

  • Animation without crash

Actual Results

  • Crash


  • This sample works on 10.11 (El Capitan)
  • It crashes on 10.12 (Sierra)

The mentioned CollectionViewMoveBug sample app is on our Radar Samples GitHub repo.

Also published on Medium.

Categories: Bug Reports

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