-[UICollectionView reloadSections:] does not remove displaying cells from UICollectionView

Originator:crazygemini.Lee
Number:rdar://21473823 Date Originated:
Status:Close Resolved:
Product:iOS Product Version:
Classification: Reproducible:
 
Summary:
The cells displayed in `UICollectionView` are not removed from it after calling `-[UICollectionView reloadSections:]`.

Steps to Reproduce:
Use this gist to reproduce this bug: https://gist.github.com/crazytonyli/2b340ca9b49143366938

1. Put the `ViewController.m` file into an iOS Xcode project.
2. Create an instance of `ViewController` and present it.
3. Run the iOS demo project, present `ViewController`.
3. Checkout the console log.
4. After the 'reload' log is shown, use Xcode's Debug View Hierarchy tool to checkout UICollectionView's subviews. 

Expected Results:
The cells count should be same before and after `reloadSections` message is sent.
Number of cells in `UICollectionView` instance should not be greater than the number of items in section 0.

Actual Results:
If run the demo project in iPhone 6 Simulator, the console output will be:

```
cells: 4
reload
cells: 8
```

Use Debug View Hierarchy tool to checkout `UICollectionView`'s subviews, we will see 8 cells, but we should only have 5 items for section 0.



Version:
iOS 8

Notes:


Configuration:
Tested on iPhone 6 Simulator

Attachments:
'Screen Shot 2015-06-20 at 7.43.20 PM.png' was successfully uploaded.

Comments

Collection view does not always remove cells from the superview when they are reused - they become hidden instead. This is correct behavior designed for maximum performance.

By crazygemini.Lee at July 8, 2015, 2:10 a.m. (reply...)

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