Fix for iOS 15 cell lifecycle behavior change

EssentialApp/EssentialAppTests/FeedUIIntegrationTests.swift

@@ -164,6 +164,23 @@ final class FeedUIIntegrationTests: XCTestCase {
         XCTAssertEqual(loader.cancelledImageURLs, [image0.url, image1.url], "Expected two cancelled image URL requests once second image is also not visible anymore")
     }
 
+    func test_feedImageView_reloadsImageURLWhenBecomingVisibleAgain() {
+        let image0 = makeImage(url: URL(string: "http://url-0.com")!)
+        let image1 = makeImage(url: URL(string: "http://url-1.com")!)
+        let (sut, loader) = makeSUT()
+
+        sut.simulateAppearance()
+        loader.completeFeedLoading(with: [image0, image1])
+
+        sut.simulateFeedImageBecomingVisibleAgain(at: 0)
+
+        XCTAssertEqual(loader.loadedImageURLs, [image0.url, image0.url], "Expected two image URL request after first view becomes visible again")
+
+        sut.simulateFeedImageBecomingVisibleAgain(at: 1)
+
+        XCTAssertEqual(loader.loadedImageURLs, [image0.url, image0.url, image1.url, image1.url], "Expected two new image URL request after second view becomes visible again")
+    }
+
     func test_feedImageViewLoadingIndicator_isVisibleWhileLoadingImage() {
         let (sut, loader) = makeSUT()
 
@@ -182,6 +199,10 @@ final class FeedUIIntegrationTests: XCTestCase {
         loader.completeImageLoadingWithError(at: 1)
         XCTAssertEqual(view0?.isShowingImageLoadingIndicator, false, "Expected no loading indicator state change for first view once second image loading completes with error")
         XCTAssertEqual(view1?.isShowingImageLoadingIndicator, false, "Expected no loading indicator for second view once second image loading completes with error")
+
+        view1?.simulateRetryAction()
+        XCTAssertEqual(view0?.isShowingImageLoadingIndicator, false, "Expected no loading indicator state change for first view once second image loading completes with error")
+        XCTAssertEqual(view1?.isShowingImageLoadingIndicator, true, "Expected loading indicator state change for second view on retry action")
     }
 
     func test_feedImageView_rendersImageLoadedFromURL() {
@@ -326,6 +347,26 @@ final class FeedUIIntegrationTests: XCTestCase {
         XCTAssertEqual(newView.renderedImage, imageData)
     }
 
+    func test_feedImageView_configuresViewCorrectlyWhenCellBecomingVisibleAgain() {
+        let (sut, loader) = makeSUT()
+
+        sut.simulateAppearance()
+        loader.completeFeedLoading(with: [makeImage()])
+
+        let view0 = sut.simulateFeedImageBecomingVisibleAgain(at: 0)
+
+        XCTAssertEqual(view0?.renderedImage, nil, "Expected no rendered image when view becomes visible again")
+        XCTAssertEqual(view0?.isShowingRetryAction, false, "Expected no retry action when view becomes visible again")
+        XCTAssertEqual(view0?.isShowingImageLoadingIndicator, true, "Expected loading indicator when view becomes visible again")
+
+        let imageData = UIImage.make(withColor: .red).pngData()!
+        loader.completeImageLoading(with: imageData, at: 1)
+
+        XCTAssertEqual(view0?.renderedImage, imageData, "Expected rendered image when image loads successfully after view becomes visible again")
+        XCTAssertEqual(view0?.isShowingRetryAction, false, "Expected no retry when image loads successfully after view becomes visible again")
+        XCTAssertEqual(view0?.isShowingImageLoadingIndicator, false, "Expected no loading indicator when image loads successfully after view becomes visible again")
+    }
+
     func test_feedImageView_doesNotRenderLoadedImageWhenNotVisibleAnymore() {
         let (sut, loader) = makeSUT()
 

EssentialApp/EssentialAppTests/Helpers/FeedViewController+TestHelpers.swift → EssentialApp/EssentialAppTests/Helpers/ListViewController+TestHelpers.swift

@@ -47,6 +47,17 @@ extension ListViewController {
         return feedImageView(at: index) as? FeedImageCell
     }
 
+    @discardableResult
+    func simulateFeedImageBecomingVisibleAgain(at row: Int) -> FeedImageCell? {
+        let view = simulateFeedImageViewNotVisible(at: row)
+
+        let delegate = tableView.delegate
+        let index = IndexPath(row: row, section: feedImagesSection)
+        delegate?.tableView?(tableView, willDisplay: view!, forRowAt: index)
+
+        return view
+    }
+
     @discardableResult
     func simulateFeedImageViewNotVisible(at row: Int) -> FeedImageCell? {
         let view = simulateFeedImageViewVisible(at: row)

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

@@ -43,6 +43,11 @@ extension FeedImageCellController: UITableViewDataSource, UITableViewDelegate, U
         return cell!
     }
 
+    public func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
+        self.cell = cell as? FeedImageCell
+        delegate.didRequestImage()
+    }
+
     public func tableView(_ tableView: UITableView, didEndDisplaying cell: UITableViewCell, forRowAt indexPath: IndexPath) {
         cancelLoad()
     }

EssentialFeed/EssentialFeediOS/Shared UI/Controllers/ListViewController.swift

@@ -82,6 +82,11 @@ public final class ListViewController: UITableViewController, UITableViewDataSou
         onViewIsAppearing?(self)
     }
 
+    public override func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
+        let dl = cellController(at: indexPath)?.delegate
+        dl?.tableView?(tableView, willDisplay: cell, forRowAt: indexPath)
+    }
+
     public override func tableView(_ tableView: UITableView, didEndDisplaying cell: UITableViewCell, forRowAt indexPath: IndexPath) {
         let dl = cellController(at: indexPath)?.delegate
         dl?.tableView?(tableView, didEndDisplaying: cell, forRowAt: indexPath)