Ensure previous cells' prepareForReuse doesn't affect new cells by re…

…moving the `onReuse` closure reference when releasing the cell for reuse.

Every time we update the table view state, existing cells can be reused for different index paths, where they'll be managed by different cell controllers - so we need to remove all references to the previous cell controllers when releasing the cell for reuse. Since the `onReuse` closure references the cell controller via `self`, we need to set `onReuse` to `nil` when releasing the cell for reuse by another cell controller. This way, we ensure there are no references to the cell controller so there will be no side effects.

EssentialApp/EssentialAppTests/FeedUIIntegrationTests.swift

@@ -518,6 +518,23 @@ class FeedUIIntegrationTests: XCTestCase {
 		XCTAssertEqual(view0.renderedImage, .none, "Expected no image state change for reused view once image loading completes successfully")
 	}
 
+	func test_feedImageView_showsDataForNewViewRequestAfterPreviousViewIsReused() throws {
+		let (sut, loader) = makeSUT()
+
+		sut.simulateAppearance()
+		loader.completeFeedLoading(with: [makeImage(), makeImage()])
+
+		let previousView = try XCTUnwrap(sut.simulateFeedImageViewNotVisible(at: 0))
+
+		let newView = try XCTUnwrap(sut.simulateFeedImageViewVisible(at: 0))
+		previousView.prepareForReuse()
+
+		let imageData = UIImage.make(withColor: .red).pngData()!
+		loader.completeImageLoading(with: imageData, at: 1)
+
+		XCTAssertEqual(newView.renderedImage, imageData)
+	}
+
 	func test_feedImageView_doesNotRenderLoadedImageWhenNotVisibleAnymore() {
 		let (sut, loader) = makeSUT()
 		sut.simulateAppearance()

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

@@ -76,6 +76,7 @@ extension FeedImageCellController: UITableViewDataSource, UITableViewDelegate, U
 	}
 
 	private func releaseCellForReuse() {
+		cell?.onReuse = nil
 		cell = nil
 	}
 }