Скачать или смотреть Solving the UICollectionView Data Source Issue in NSObject Class

Learn how to properly implement a `UICollectionView` within an `NSObject` class in Swift, ensuring it displays data correctly in your views.
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This video is based on the question https://stackoverflow.com/q/71261124/ asked by the user 'Mach' ( https://stackoverflow.com/u/18305061/ ) and on the answer https://stackoverflow.com/a/71261557/ provided by the user 'Shawn Frank' ( https://stackoverflow.com/u/1619193/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding UICollectionView Issues in NSObject Class

If you've been working with Swift and have tried to implement a UICollectionView within an NSObject class, you may find yourself facing a frustrating issue: the collection view displays, but the cells' data never appear, and you can't change the cell's background color as intended. In this guide, we will discuss why this happens and provide a clear solution to ensure your UICollectionView works as expected.

The Problem

When you create a UICollectionView in an NSObject-derived class, one common mistake is to instantiate your collection view controller in viewDidLoad as a local variable. For example:

[[See Video to Reveal this Text or Code Snippet]]

The problem arises because local variables like this do not persist beyond their immediate scope. Once the viewDidLoad method finishes executing, the object you created is released from memory, which means it no longer acts as the data source or delegate for the UICollectionView. Consequently, your cells do not display the expected data.

The Solution

To resolve this issue, follow these steps to ensure that your UICollectionView can access the data source and delegate correctly throughout its lifecycle.

1. Maintain a Strong Reference

Instead of creating a local variable, you need to maintain a strong reference to the CellClass instance in your view controller. This can be done by making it a property of your view controller class. Here's how:

[[See Video to Reveal this Text or Code Snippet]]

2. Check for Proper Deinitialization

To further troubleshoot, you can add a deinit to the CellClass to verify that it's being properly allocated and deallocated:

[[See Video to Reveal this Text or Code Snippet]]

This helps you ensure that your instance is not being prematurely released, which would indicate that you still have issues with its lifecycle management.

3. Register and Configure the Collection View Correctly

Your existing implementation where you register the cell and assign delegates is mostly correct. Just ensure those parts are executed as intended:

Make sure you register your Cell class with the correct identifier.

Ensure you set the delegate and dataSource of the UICollectionView to self, which you seem to have done properly already.

4. Testing Changes

After making the aforementioned changes, run your application again. You should see the cells being populated correctly with the sample text "test," and they should have the black background as specified in your cellForItemAt method.

Conclusion

By maintaining a strong reference to the CellClass instance within your view controller, you can ensure that your UICollectionView displays the intended data and behaves correctly. This approach will save you from the pitfalls of local variables that vanish after viewDidLoad and keep your application running smoothly.

By following these structured steps, you’ll troubleshoot and fix the issue of the non-displaying UICollectionView cells, ensuring a seamless user experience in your app. Happy coding!