Fix potential crash on didEndDisplayingCell

EssentialApp/EssentialAppTests/FeedUIIntegrationTests.swift

@@ -78,6 +78,20 @@ final class FeedUIIntegrationTests: XCTestCase {
         assertThat(sut, isRendering: [image0, image1, image2, image3])
     }
 
+    func test_loadFeedCompletion_rendersSuccessfullyLoadedEmptyFeedAfterNonEmptyFeed() {
+        let image0 = makeImage()
+        let image1 = makeImage()
+        let (sut, loader) = makeSUT()
+
+        sut.simulateAppearance()
+        loader.completeFeedLoading(with: [image0, image1], at: 0)
+        assertThat(sut, isRendering: [image0, image1])
+
+        sut.simulateUserInitiatedFeedReload()
+        loader.completeFeedLoading(with: [], at: 1)
+        assertThat(sut, isRendering: [])
+    }
+
     func test_loadFeedCompletion_doesNotAlterCurrentRenderingStateOnError() {
         let image0 = makeImage()
         let (sut, loader) = makeSUT()

EssentialApp/EssentialAppTests/Helpers/FeedUIIntegrationTests+Assertions.swift

@@ -10,13 +10,17 @@ import EssentialFeediOS
 extension FeedUIIntegrationTests {
 
     func assertThat(_ sut: FeedViewController, isRendering feed: [FeedImage], file: StaticString = #file, line: UInt = #line) {
+        sut.view.enforceLayoutCycle()
+
         guard sut.numberOfRenderedFeedImageViews() == feed.count else {
             return XCTFail("Expected \(feed.count) images, got \(sut.numberOfRenderedFeedImageViews()) instead.", file: file, line: line)
         }
 
         feed.enumerated().forEach { index, image in
             assertThat(sut, hasViewConfiguredFor: image, at: index, file: file, line: line)
         }
+
+        executeRunLoopToCleanUpReferences()
     }
 
     func assertThat(_ sut: FeedViewController, hasViewConfiguredFor image: FeedImage, at index: Int, file: StaticString = #file, line: UInt = #line) {
@@ -34,4 +38,8 @@ extension FeedUIIntegrationTests {
         XCTAssertEqual(cell.descriptionText, image.description, "Expected description text to be \(String(describing: image.description)) for image view at index (\(index)", file: file, line: line)
     }
 
+    private func executeRunLoopToCleanUpReferences() {
+        RunLoop.current.run(until: Date())
+    }
+
 }

EssentialApp/EssentialAppTests/Helpers/FeedViewController+TestHelpers.swift

@@ -18,9 +18,14 @@ extension FeedViewController {
     }
 
     private func prepareForFirstAppearance() {
+        setSmallFrameToPreventRenderingCells()
         replaceRefreshControlWithFakeForiOS17PlusSupport()
     }
 
+    private func setSmallFrameToPreventRenderingCells() {
+        tableView.frame = CGRect(x: 0, y: 0, width: 390, height: 1)
+    }
+
     private func replaceRefreshControlWithFakeForiOS17PlusSupport() {
         let spyRefreshControl = UIRefreshControlSpy()
 

EssentialApp/EssentialAppTests/Helpers/UIView+TestHelpers.swift

@@ -0,0 +1,13 @@
+//
+// Created by Rodrigo Porto.
+// Copyright © 2025 PortoCode. All Rights Reserved.
+//
+
+import UIKit
+
+extension UIView {
+    func enforceLayoutCycle() {
+        layoutIfNeeded()
+        RunLoop.current.run(until: Date())
+    }
+}

EssentialFeed/EssentialFeediOS/Feed UI/Controllers/FeedViewController.swift

@@ -13,12 +13,14 @@ public protocol FeedViewControllerDelegate {
 public final class FeedViewController: UITableViewController, UITableViewDataSourcePrefetching, FeedLoadingView, FeedErrorView {
     @IBOutlet private(set) public var errorView: ErrorView?
 
+    private var loadingControllers = [IndexPath: FeedImageCellController]()
+
     private var tableModel = [FeedImageCellController]() {
         didSet { tableView.reloadData() }
     }
 
     private var onViewIsAppearing: ((FeedViewController) -> Void)?
-        
+
     public var delegate: FeedViewControllerDelegate?
 
     public override func viewDidLoad() {
@@ -43,6 +45,7 @@ public final class FeedViewController: UITableViewController, UITableViewDataSou
     }
 
     public func display(_ cellControllers: [FeedImageCellController]) {
+        loadingControllers = [:]
         tableModel = cellControllers
     }
 
@@ -83,10 +86,13 @@ public final class FeedViewController: UITableViewController, UITableViewDataSou
     }
 
     private func cellController(forRowAt indexPath: IndexPath) -> FeedImageCellController {
-        return tableModel[indexPath.row]
+        let controller = tableModel[indexPath.row]
+        loadingControllers[indexPath] = controller
+        return controller
     }
 
     private func cancelCellControllerLoad(forRowAt indexPath: IndexPath) {
-        cellController(forRowAt: indexPath).cancelLoad()
+        loadingControllers[indexPath]?.cancelLoad()
+        loadingControllers[indexPath] = nil
     }
 }

EssentialFeed/EssentialFeediOS/Feed UI/Views/Feed.storyboard

@@ -20,7 +20,7 @@
                             <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMaxY="YES"/>
                             <subviews>
                                 <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Error label" textAlignment="center" lineBreakMode="tailTruncation" numberOfLines="0" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="5A2-jn-0GF">
-                                    <rect key="frame" x="0.0" y="0.0" width="393" height="34"/>
+                                    <rect key="frame" x="0.0" y="8" width="393" height="18"/>
                                     <gestureRecognizers/>
                                     <fontDescription key="fontDescription" type="system" pointSize="17"/>
                                     <color key="textColor" white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
@@ -33,9 +33,9 @@
                             <color key="backgroundColor" red="1" green="0.41568627450980389" blue="0.41568627450980389" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                             <gestureRecognizers/>
                             <constraints>
-                                <constraint firstItem="5A2-jn-0GF" firstAttribute="top" secondItem="4rO-dP-KUh" secondAttribute="top" id="LuN-ci-cAl"/>
+                                <constraint firstItem="5A2-jn-0GF" firstAttribute="top" secondItem="4rO-dP-KUh" secondAttribute="top" constant="8" id="LuN-ci-cAl"/>
                                 <constraint firstItem="5A2-jn-0GF" firstAttribute="leading" secondItem="4rO-dP-KUh" secondAttribute="leading" id="SKs-H9-mIi"/>
-                                <constraint firstAttribute="bottom" secondItem="5A2-jn-0GF" secondAttribute="bottom" id="aPC-fa-cWF"/>
+                                <constraint firstAttribute="bottom" secondItem="5A2-jn-0GF" secondAttribute="bottom" constant="8" id="aPC-fa-cWF"/>
                                 <constraint firstAttribute="trailing" secondItem="5A2-jn-0GF" secondAttribute="trailing" id="fXX-CP-YAQ"/>
                             </constraints>
                             <connections>