DemoPerformBatchUpdates

In this demo, we'll do an experiment about UICollectionView.performBatchUpdates() func. We'll try 2 ways to implement this func

1. Remove element at index (1) 3 times in data source and also in collection view
2. Remove element at index (3) (2) (1) in data source and in collection view

Try it yourself by these actions:

• Tap Wrong Action button to try action (1)
• Tap Correct Action button to try action (2)
• Remember to Reset after each action.

So some sequences you can try:

1. Wrong Action => Reset => Correct Action
2. Wrong Action => Reset => Wrong Action => ... (Loop)
3. Correct Action => Reset => Correct Action => ... (Loop)

Some behaviors can be observed according to each sequence

1. Sequence 1: Wrong Action shows wrong UI, Correct Action shows correct UI
2. Sequence 2: App crashes, exception raises at the 2nd or 3rd loop.
3. Sequence 3: Correct UI, app works well.

The crash for Sequence 2 maybe either one of these