Fix crash upon SwiftUICollectionViewCell deinit and add some more breadcrumbs and optimization in HomeViewModel snapshot calculation and rendering

PocketKit/Sources/PocketKit/Collections/CollectionViewController.swift

@@ -309,7 +309,7 @@ private extension CollectionViewController {
             return cell
         case .error:
             let cell: EmptyStateCollectionViewCell = collectionView.dequeueCell(for: indexPath)
-            cell.configure(parent: self, model.errorEmptyState)
+            cell.configure(viewModel: model.errorEmptyState)
             return cell
         }
     }

PocketKit/Sources/PocketKit/Home/HomeViewController.swift

@@ -19,7 +19,7 @@ struct HomeViewControllerSwiftUI: UIViewControllerRepresentable {
 
     func makeUIViewController(context: UIViewControllerRepresentableContext<Self>) -> UINavigationController {
         let homeViewController = HomeViewController(model: model)
-        homeViewController.updateHeroCardCount()
+        homeViewController.updateLayout()
         let navigationController = UINavigationController(rootViewController: homeViewController)
         navigationController.navigationBar.prefersLargeTitles = true
         navigationController.navigationBar.barTintColor = UIColor(.ui.white1)
@@ -154,6 +154,7 @@ class HomeViewController: UIViewController {
                     return
                 }
                 dataSource.apply(snapshot)
+                Log.breadcrumb(category: "home", level: .debug, message: "➡️ Applying snapshot - #sections: \(snapshot.numberOfSections), #items: \(snapshot.numberOfItems)")
             }.store(in: &subscriptions)
     }
 
@@ -216,14 +217,14 @@ class HomeViewController: UIViewController {
     }
 
     override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
-        updateHeroCardCount()
+        updateLayout()
     }
 
-    func updateHeroCardCount() {
+    fileprivate func updateLayout() {
         if traitCollection.shouldUseWideLayout() {
-            self.model.numberOfHeroItems = 2
+            model.useWideLayout()
         } else {
-            self.model.numberOfHeroItems = 1
+            model.useCompactLayout()
         }
     }
 }

PocketKit/Sources/PocketKit/Home/HomeViewModel.swift

@@ -124,11 +124,7 @@ class HomeViewModel: NSObject {
 
     @Published var tappedSeeAll: SeeAll?
 
-    var numberOfHeroItems: Int = 1 {
-        didSet {
-            self.snapshot = buildSnapshot()
-        }
-    }
+    private var numberOfHeroItems: Int = 1
 
     private let source: Source
     let tracker: Tracker
@@ -311,6 +307,27 @@ extension HomeViewModel {
         }
         return snapshot
     }
+
+    /// Updates the collection view layout for compact or wide layout, if this changed.
+    /// Wide layout has two columns and two hero items per recommendation section.
+    /// - Parameter heroItems: the number of hero items to use.
+    private func updateLayout(_ heroItems: Int) {
+        guard heroItems != numberOfHeroItems else {
+            return
+        }
+        numberOfHeroItems = heroItems
+        snapshot = buildSnapshot()
+    }
+
+    /// Updates the layout to wide, if the previous layout was compact.
+    func useWideLayout() {
+        updateLayout(2)
+    }
+
+    /// Updates the layout to compact, if the previpus layout was wide.
+    func useCompactLayout() {
+        updateLayout(1)
+    }
 }
 
 // MARK: - Cell Selection
@@ -618,10 +635,11 @@ extension HomeViewModel {
 
 // MARK: - Loading Section
 extension HomeViewModel {
-    static func loadingSnapshot() -> Snapshot {
+    private static func loadingSnapshot() -> Snapshot {
         var snapshot = Snapshot()
         snapshot.appendSections([.loading])
         snapshot.appendItems([.loading], toSection: .loading)
+        Log.breadcrumb(category: "home", level: .debug, message: "➡️ Sending loading snapshot.")
         return snapshot
     }
 }

PocketKit/Sources/PocketKit/MyList/EmptyStates/EmptyStateView.swift

@@ -6,37 +6,33 @@ import SwiftUI
 import Textile
 
 open class SwiftUICollectionViewCell<T>: UICollectionViewCell where T: View {
-    private(set) var hosting: UIHostingController<T>?
-
-    func embed(in parent: UIViewController, withView content: T) {
-        if let hosting = self.hosting {
-            hosting.rootView = content
-            hosting.view.layoutIfNeeded()
-        } else {
-            let hosting = UIHostingController(rootView: content)
-            parent.addChild(hosting)
-            hosting.didMove(toParent: parent)
-            self.contentView.addSubview(hosting.view)
-            self.hosting = hosting
-        }
-    }
-
-    deinit {
-        Task { @MainActor in
-            hosting?.willMove(toParent: nil)
-            hosting?.view.removeFromSuperview()
-            hosting?.removeFromParent()
-            hosting = nil
-        }
+    /// Conveets  a `SwiftUI View` in a `UIKit UIView`
+    /// - Parameters:
+    ///   - content: the `SwiftUI View`
+    /// - Returns: the `UIKit View` that embeds the original `SwiftUI View`
+    func uiView(from content: T) -> UIView {
+        let controller = UIHostingController(rootView: content)
+        controller.view.translatesAutoresizingMaskIntoConstraints = false
+        controller.view.backgroundColor = .clear
+        return controller.view
     }
 }
 
 class EmptyStateCollectionViewCell: SwiftUICollectionViewCell<EmptyStateView<EmptyView>> {
-    func configure(parent: UIViewController, _ viewModel: EmptyStateViewModel) {
-        embed(in: parent, withView: EmptyStateView(viewModel: viewModel))
-        hosting?.view.frame = self.contentView.bounds
-        hosting?.view.backgroundColor = .clear
-        hosting?.view.accessibilityIdentifier = viewModel.accessibilityIdentifier
+    func configure(viewModel: EmptyStateViewModel) {
+        let view = uiView(from: EmptyStateView(viewModel: viewModel))
+        contentView.addSubview(view)
+        contentView.pinSubviewToAllEdges(view)
+        view.accessibilityIdentifier = viewModel.accessibilityIdentifier
+    }
+
+    override func prepareForReuse() {
+        // default implementation does nothing, adding it here just in case it changes in the future
+        super.prepareForReuse()
+        // clear up any existing content from the view before adding one
+        contentView.subviews.forEach {
+            $0.removeFromSuperview()
+        }
     }
 }
 

PocketKit/Sources/PocketKit/MyList/ItemsList/UIKit/ItemsListViewController.swift

@@ -379,7 +379,7 @@ class ItemsListViewController<ViewModel: ItemsListViewModel>: UIViewController,
         guard let viewModel = model.emptyState else {
             return
         }
-        cell.configure(parent: self, viewModel)
+        cell.configure(viewModel: viewModel)
     }
 
     private func handle(savesEvent event: ItemsListEvent<ViewModel.ItemIdentifier>) {