I was reading over the documentation of the CellProvider struct for the diffable data source initialiser, and the CellProvider is defined as a closure which takes three arguments, a table view, an index path, and an item identifier. My question is, who vends the index path and the item identifier to this closure? My thinking is that it is the data source who vends these items because it adopts the UITableViewDataSource protocol which acts as the source of data for this view.

Hello, I am trying to implement a subscriber which specifies its own demand for how many elements it wants to receive from a publisher. My code is below: import Combine var array = [1, 2, 3, 4, 5, 6, 7] struct ArraySubscriber<T>: Subscriber { typealias Input = T typealias Failure = Never let combineIdentifier = CombineIdentifier() func receive(subscription: any Subscription) { subscription.request(.max(4)) } func receive(_ input: T) -> Subscribers.Demand { print("input,", input) return .max(4) } func receive(completion: Subscribers.Completion<Never>) { switch completion { case .finished: print("publisher finished normally") case .failure(let failure): print("publisher failed due to, ", failure) } } } let subscriber = ArraySubscriber<Int>() array.publisher.subscribe(subscriber) According to Apple's documentation, I specify the demand inside the receive(subscription: any Subscription) method, see link. But when I run this code I get the following output: input, 1 input, 2 input, 3 input, 4 input, 5 input, 6 input, 7 publisher finished normally Instead, I expect the subscriber to only "receive" elements 1, 2, 3, 4 from the array. How can I accomplish this?

Hello, I have a collection view that uses a diffable data source, and I am initiating an API call while configuring a cell RuntimeCell in the cell registration block inside setupDataSource(). The cell has a runtimeLabel property whose text I am setting inside a configureLabel(movieId:) function. I noticed that the collection view does not automatically refresh the text label once this API call finishes and after setting the text property on a UILabel in the collection view cell to a value retrieved during the API call. I presume this is because I need to call dataSource.apply(snapshot) myself to reload the changes in the collection view after the API call finishes retrieving the runtime data. However, since the API call happens via the configuration of the cell in the cell registration closure, this API call ends up being called infinitely if I call dataSource.apply(snapshot) every time the API call finishes (i.e. calling dataSource.applySnapshot() calls the closure for the cell registration handler which re-triggers the API call). What is the correct architecture to apply to accomplish reloading the collection view so that the text label appears once the API finishes calling? Thank you class MovieDetailViewController: UIViewController { func setupDataSource() { // ... let runTimeCellRegistration = UICollectionView.CellRegistration<RuntimeCell, Item> { cell, indexPath, item in cell.runtimeLabelDelegate = self cell.configureLabel(movieId: self.selectedMovie.id) } dataSource = UICollectionViewDiffableDataSource(collectionView: collectionView, cellProvider: { collectionView, indexPath, itemIdentifier in let section = Section(rawValue: indexPath.section) switch section { //... case .runtime: return collectionView.dequeueConfiguredReusableCell(using: runTimeCellRegistration, for: indexPath, item: itemIdentifier) //... } return nil }) } } protocol RuntimeLabelCellDelegate: AnyObject { func didUpdateRuntime() } class RuntimeCell: UICollectionViewCell { var runtimeLabel: UILabel! //... UI Setup func configureLabel(movieId: Int) { Task { do { let details = try await movieSearchService.fetchMovieDetails(movieId: movieId) await MainActor.run { let minutes = details.runTime let durationText = "\(minutes)m" var emojiText = "" if minutes < 90 { emojiText = "Short & Sweet ⚡️" } else if minutes > 150 { emojiText = "Get the snacks ready 🍿" } runtimeLabel.text = emojiText.isEmpty ? durationText : "\(durationText) • \(emojiText)" runtimeLabelDelegate?.didUpdateRuntime() } } catch { print("Failed to load details: \(error)") } } } } extension MovieDetailViewController: RuntimeLabelCellDelegate { func didUpdateRuntime() { var snapshot = dataSource.snapshot() snapshot.appendItems([.runtime], toSection: .runtime) dataSource.apply(snapshot, animatingDifferences: true) } }

I was trying to register a UICollectionReusableView in my UICollectionView.SupplementaryRegistration handler in order to apply a content configuration to apply the text and secondaryText properties to the reusable view. However, when I try to apply the content configuration on the header view object that I return in my cell registration handler, I get an error that says: "Value of type 'UICollectionReusableView' has no member 'contentConfiguration'". How can apply content configuration to a UICollectionReusableView? This is my code: let headerRegistration = UICollectionView.SupplementaryRegistration<UICollectionReusableView>(elementKind: UICollectionView.elementKindSectionHeader) { header, elementKind, indexPath in // Header configuration is handled in the header's init var configuration = UIListContentConfiguration.plainHeader() configuration.text = "Current Emotional State" configuration.secondaryText = "What best describes how you're feeling right now?" header.contentConfiguration = configuration }

I was writing some code for a UICollectionViewCell class and I normally include this initialiser when I create a new subclass for UICollectionViewCell, and saw that frequently this is paired with a required init?(coder: NSCoder) initialiser, so I was wondering if super.init(frame: CGRect) is the designated initialiser for the UICollectionViewCell class?

Hi, I have two views in my view hierarchy searchButtonView and searchBarView. I am trying to fade out the searchButtonView while animating the change in the frame of searchBarView simultaneously within a UIView.animate block. However, when I run the app, the frame of searchBarView resizes correctly while the alpha of searchButtonView does not animate to 0 as expected. How can I fix this so that both view animate simultaneously? Please see my code below. Thank you class MovieTitlesViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view. } var searchButtonView: UIView! var searchBarView: UIView! override func viewDidLayoutSubviews() { createSearchButtonView() createSearchBarView() } func createSearchButtonView() { searchButtonView = UIView(frame: CGRect(x: 23, y: view.safeAreaInsets.top, width: 48, height: 48)) let searchImageView = UIImageView(image: UIImage(named: "Search Icon")!) searchImageView.frame = CGRect(x: searchButtonView.frame.width / 2 - 16, y: searchButtonView.frame.height / 2 - 16, width: 32, height: 32) searchButtonView.addSubview(searchImageView) searchButtonView.backgroundColor = .blue searchButtonView.layer.cornerRadius = 24 searchButtonView.layer.borderColor = UIColor.gray.cgColor searchButtonView.layer.borderWidth = 0.5 let tapGesture = UITapGestureRecognizer(target: self, action: #selector(tappedSearchView)) tapGesture.numberOfTapsRequired = 1 searchButtonView.addGestureRecognizer(tapGesture) searchButtonView.isUserInteractionEnabled = true view.addSubview(searchButtonView) } func createSearchBarView() { searchBarView = UIView(frame: CGRect(x: 23, y: view.safeAreaInsets.top, width: 0, height: 48)) searchBarView.backgroundColor = .red // searchBarView.backgroundColor = UIColor(red: 217/255, green: 217/255, blue: 217/255, alpha: 1.0) searchBarView.layer.cornerRadius = 24 searchBarView.layer.borderColor = UIColor.gray.cgColor searchBarView.layer.borderWidth = 0.5 view.addSubview(searchBarView) } func animateExpandSearchView() { UIView.animate(withDuration: 0.25, delay: 0.0, options: .curveEaseInOut) { self.searchButtonView.alpha = 0.0 self.searchBarView.frame = CGRect(x: 23, y: self.view.safeAreaInsets.top, width: UIScreen.main.bounds.width - 46, height: 48) } } @objc func tappedSearchView() { print("tapped search view") animateExpandSearchView() } }

Hi, I have added a UILabel to my collection view cell programmatically and have set up constraints using auto layout. The centerX and centerY constraints of the label are equal to the centerX and centerY anchors of the content view. However, the label is appearing in the top left corner of the cell rather than in the center where I expect it to be. Here is my code: protocol TapLabelCollectionViewCellDelegate: AnyObject { func incrementNumberOfTaps(index: Int) } class TapLabelCollectionViewCell: UICollectionViewCell { var taplabel: UILabel! var delegate: TapLabelCollectionViewCellDelegate? var index: Int! static let identifier = "tapLabelCellIdentifier" override init(frame: CGRect) { super.init(frame: frame) taplabel = UILabel() taplabel.translatesAutoresizingMaskIntoConstraints = false addSubview(taplabel) NSLayoutConstraint.activate([ taplabel.centerXAnchor.constraint(equalTo: contentView.centerXAnchor), taplabel.centerYAnchor.constraint(equalTo: contentView.centerYAnchor) ]) setUpTapGestureRecognizer() } required init?(coder: NSCoder) { super.init(coder: coder) } func setUpTapGestureRecognizer() { let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(incrementNumberOfTaps)) print("tap Label,", taplabel) taplabel.addGestureRecognizer(tapGestureRecognizer) } @objc func incrementNumberOfTaps() { delegate?.incrementNumberOfTaps(index: index) } } I am also getting the following warning in Xcode

I connected a tap gesture recogniser to a label in storyboard by dragging a tap gesture recogniser object onto the label. When I connect the outlet to the gesture recogniser I get this error: How can I connect the tap gesture recogniser in storyboard to my code?

When I set up a UICollectionReusableView cell in storyboard and try to dequeue a cell of this type, my app crashes with this error message: Steps I've gone through to add my collection reusable view in storyboard: I added a collection reusable view by dragging the item from the panel of objects to my collection view. I created a class called EmotionFiltersHeaderView which subclasses UICollectionReusableView that contains a reference to an IBOutlet var for the label I added to the reusable view (also in storyboard). I changed the class name of the reusable view in the storyboard to my custom class name, EmotionFiltersHeaderView. I added an identifier to the reusable view and called it "emotionFiltersHeaderReusableView". I've included the header view in the boundary supplementary items property of the section where I'm adding the header view. This is my code: `let headerSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1.0), heightDimension: .estimated(37.0)) let header = NSCollectionLayoutBoundarySupplementaryItem( layoutSize: headerSize, elementKind: UICollectionView.elementKindSectionHeader, alignment: .topLeading) section.boundarySupplementaryItems = [header] emotionFiltersDataSource.supplementaryViewProvider = { collectionView, kind, indexPath in guard let headerView = collectionView.dequeueReusableSupplementaryView( ofKind: ElementKind.sectionHeader.rawValue, withReuseIdentifier: "emotionFiltersHeaderReusableView", for: indexPath ) as? EmotionFiltersHeaderView else { fatalError("Could not dequeue header view as EmotionFiltersHeaderView") } let sectionTitle = Section.allCases[indexPath.section].rawValue headerView.sectionTitleLabel.text = sectionTitle return headerView } enum ElementKind: String { case sectionHeader = "section-header-element-kind" }`

The documentation for UIListContentConfiguration states that I can get the default content configuration of a UICollectionViewCell by getting the cells default content configuration. In practice, however, this presents an error in the compiler: let choiceRegistration = UICollectionView.CellRegistration<UICollectionViewCell, SurveyItem> { cell, indexPath, item in cell.configurationUpdateHandler = { cell, state in switch item.type { case .choice(let letter, let text): cell.defaultContentConfiguration() ... } The error shown when calling cell.defaultContentConfiguration() is Value of type 'UICollectionViewCell' has no member 'defaultContentConfiguration'. Instead, I need to initialise a content configuration using UIListContentConfiguration.cell() to get the default content configuration. This needs to be reflected in the documentation in UIKit.

Hi, I would like to modify an associated value of an existing enum instance of the the following enum: enum FilterItem: Equatable, Hashable { case work(isSelected: Bool) ... var filterName: String { switch self { case .work: return "Work" ... } } var isSelected: Bool { switch self { case .work(let isSelected): return isSelected ... } } I want to be able to switch on the FilterItem type and then to be able to modify the isSelected property of the instance like: let itemToChange: FilterItem switch item { case .work(let isSelected): itemToChange.isSelected = !isSelected I know the above code doesn't compile, but I was wondering if there was a way I could modify my enum instance without creating a totally new enum instance.

I have added a UICollectionViewCell to my storyboard, and I added a UILabel to my UICollectionViewCell in storyboard. I have created a cell registration using UICollectionView.CellRegistration and have implemented the cellProvider closure for the datasource which dequeue a collection view cell of type TapLabelCollectionViewCell(I have subclassed the cell in my storyboard to this class). In my TapLabelCollectionViewCell, I am trying to set the tap gesture recogniser on the label, but the label appears nil, which I've connected using an @IBOutlet. Why is this and how can I fix it? My code : // UI View Controller: class TapGridViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view. tapGridCollectionView.collectionViewLayout = createLayout() configureDataSource() applySnapshot() } func configureDataSource() { let cellRegistration = UICollectionView.CellRegistration<TapLabelCollectionViewCell, CellItem>(handler: { (cell: TapLabelCollectionViewCell, indexPath: IndexPath, item: CellItem) in cell.taplabel.text = String(item.labelCount) }) dataSource = UICollectionViewDiffableDataSource(collectionView: tapGridCollectionView, cellProvider: { (collectionView: UICollectionView, indexPath: IndexPath, item: CellItem) in let cell = collectionView.dequeueConfiguredReusableCell(using: cellRegistration, for: indexPath, item: item) cell.delegate = self cell.index = indexPath.row return cell }) } } // UI Collection View Cell: protocol TapLabelCollectionViewCellDelegate: AnyObject { func incrementNumberOfTaps(index: Int) } class TapLabelCollectionViewCell: UICollectionViewCell { @IBOutlet var taplabel: UILabel! var delegate: TapLabelCollectionViewCellDelegate? var index: Int! static let identifier = "tapLabelCellIdentifier" override init(frame: CGRect) { super.init(frame: frame) setUpTapGestureRecognizer() } required init?(coder: NSCoder) { super.init(coder: coder) } func setUpTapGestureRecognizer() { let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(incrementNumberOfTaps)) print("tap Label,", taplabel) taplabel.addGestureRecognizer(tapGestureRecognizer) } @objc func incrementNumberOfTaps() { delegate?.incrementNumberOfTaps(index: index) } }

I have set up a collection view cell programmatically which I am registering in the cell registration of a diffable data source. I have set up a delegate for the cell, and the view controller which contains the collection view as the delegate for the cell. However, calling the cell delegate method from the cell is not calling the method in the view controller. This is my code: `// in my view controller: cell.delegate = self // in my collection view cell: delegate?.repromptLLMForIconName(iconName, index: index, emotion: emotion, red: red, green: green, blue: blue) ` But although the delegate method in the collection view gets called, my method implementation in the view controller does not. What could possibly be going wrong?