How do I properly return a CollectionViewCell with reuseIdentifier if weak self is nil in RxDataSource function?

Question

I have an issue where [unowned self] was changed to [weak self] within the dataSource function used for a CollectionView using RxDataSource due to a memory leak. I now received a crash from returning a blank collectionViewCell that doesn't have a reuseIdentifier. I understand that I need to return a cell with a reuseID.

What changes are suggested to deal with this properly?

Someone suggested making collectionView.dataSource = nil in viewDidLoad() would fix this...

I was thinking instead of returning CanvasItemCollectionViewCell() in the 'guard' check, I return collectionView.dequeueReusableCell(for: indexPath, cellType: CanvasItemCollectionViewCell.self), but if self = self fails wouldn't that mean the collectionView is garbage?

This is a difficult problem to debug because this crash doesn't happen consistently.

Here are some screenshots to portray what I am looking at.

RxDataSource code:

func dataSource()
        -> RxCollectionViewSectionedAnimatedDataSource<CanvasSectionModel> {
        RxCollectionViewSectionedAnimatedDataSource<CanvasSectionModel>(
            animationConfiguration: AnimationConfiguration(
                insertAnimation: .fade,
                reloadAnimation: .fade,
                deleteAnimation: .fade
            ),
            configureCell: { [weak self] dataSource, collectionView, indexPath, _ in
                guard let self = self else { return CanvasItemCollectionViewCell() }
                
                switch dataSource[indexPath] {
                case let .CellModel(model):
                    let cell = collectionView
                        .dequeueReusableCell(
                            for: indexPath,
                            cellType: CanvasItemCollectionViewCell.self
                        )

                    cell.model = model

                    cell.onDeleteHandler = { _ in
                        self.presentDeleteConfirmation { deleteConfirmed in
                            guard deleteConfirmed else { return }
                            self.viewModel.inputs.deletePage(withProofID: model.id)
                        }
                    }

                    return cell
                }
            }

Crash:

score 1 · Accepted Answer · answered Jun 10 '21 at 18:58

Ultimately, the problem is here:

cell.onDeleteHandler = { _ in
    self.presentDeleteConfirmation { deleteConfirmed in
        guard deleteConfirmed else { return }
        self.viewModel.inputs.deletePage(withProofID: model.id)
    }
}

Don't use self and you won't have a problem with self references so you won't need to import a weak self and then worry about the guard let self...

For the first self reference, replace it with UIViewController.top() (see below for implementation.)
For the second self reference, capture viewModel instead.

extension UIViewController {
    static func top() -> UIViewController {
        guard let rootViewController = UIApplication.shared.delegate?.window??.rootViewController else { fatalError("No view controller present in app?") }
        var result = rootViewController
        while let vc = result.presentedViewController, !vc.isBeingDismissed {
            result = vc
        }
        return result
    }
}

I ended up just encapsulating the entire assignment of the `onDeleteHandler` to a closure like so `func dataSource(onDelete: @escaping (CanvasEntity)->() )` and `cell.onDeleteHandler = { _ in onDelete(model) }` allowing me to remove both self references. Thanks — Weston Mitchell, Jun 10 '21 at 21:01

How do I properly return a CollectionViewCell with reuseIdentifier if weak self is nil in RxDataSource function?

RxDataSource code:

Crash:

1 Answers1