Replace Combine with async/await on Image Comments feature

Author: caiozullo

EssentialApp/EssentialApp/CommentsUIComposer.swift

@@ -3,18 +3,17 @@
 //
 
 import UIKit
-import Combine
 import EssentialFeed
 import EssentialFeediOS
 
 @MainActor
 public final class CommentsUIComposer {
 	private init() {}
 
-	private typealias CommentsPresentationAdapter = LoadResourcePresentationAdapter<[ImageComment], CommentsViewAdapter>
+	private typealias CommentsPresentationAdapter = AsyncLoadResourcePresentationAdapter<[ImageComment], CommentsViewAdapter>
 
 	public static func commentsComposedWith(
-		commentsLoader: @escaping () -> AnyPublisher<[ImageComment], Error>
+		commentsLoader: @escaping () async throws -> [ImageComment]
 	) -> ListViewController {
 		let presentationAdapter = CommentsPresentationAdapter(loader: commentsLoader)
 

EssentialApp/EssentialApp/SceneDelegate.swift

@@ -5,7 +5,6 @@
 import os
 import UIKit
 import CoreData
-import Combine
 import EssentialFeed
 
 class SceneDelegate: UIResponder, UIWindowSceneDelegate {
@@ -83,16 +82,14 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate {
 
 	private func showComments(for image: FeedImage) {
 		let url = ImageCommentsEndpoint.get(image.id).url(baseURL: baseURL)
-		let comments = CommentsUIComposer.commentsComposedWith(commentsLoader: makeRemoteCommentsLoader(url: url))
+		let comments = CommentsUIComposer.commentsComposedWith(commentsLoader: loadComments(url: url))
 		navigationController.pushViewController(comments, animated: true)
 	}
 
-	private func makeRemoteCommentsLoader(url: URL) -> () -> AnyPublisher<[ImageComment], Error> {
+	private func loadComments(url: URL) -> () async throws -> [ImageComment] {
 		return { [httpClient] in
-			return httpClient
-				.getPublisher(url: url)
-				.tryMap(ImageCommentsMapper.map)
-				.eraseToAnyPublisher()
+			let (data, response) = try await httpClient.get(from: url)
+			return try ImageCommentsMapper.map(data, from: response)
 		}
 	}
 

EssentialApp/EssentialAppTests/CommentsUIIntegrationTests.swift

@@ -3,7 +3,6 @@
 //
 
 import XCTest
-import Combine
 import UIKit
 import EssentialApp
 import EssentialFeed
@@ -12,15 +11,15 @@ import EssentialFeediOS
 @MainActor
 class CommentsUIIntegrationTests: XCTestCase {
 
-	func test_commentsView_hasTitle() {
+	func test_commentsView_hasTitle() async {
 		let (sut, _) = makeSUT()
 
 		sut.simulateAppearance()
 
 		XCTAssertEqual(sut.title, commentsTitle)
 	}
 
-	func test_loadCommentsActions_requestCommentsFromLoader() {
+	func test_loadCommentsActions_requestCommentsFromLoader() async {
 		let (sut, loader) = makeSUT()
 		XCTAssertEqual(loader.loadCommentsCallCount, 0, "Expected no loading requests before view appears")
 
@@ -30,16 +29,16 @@ class CommentsUIIntegrationTests: XCTestCase {
 		sut.simulateUserInitiatedReload()
 		XCTAssertEqual(loader.loadCommentsCallCount, 1, "Expected no request until previous completes")
 
-		loader.completeCommentsLoading(at: 0)
+		await loader.completeCommentsLoading(at: 0)
 		sut.simulateUserInitiatedReload()
 		XCTAssertEqual(loader.loadCommentsCallCount, 2, "Expected another loading request once user initiates a reload")
 
-		loader.completeCommentsLoading(at: 1)
+		await loader.completeCommentsLoading(at: 1)
 		sut.simulateUserInitiatedReload()
 		XCTAssertEqual(loader.loadCommentsCallCount, 3, "Expected yet another loading request once user initiates another reload")
 	}
 
-	func test_loadCommentsActions_runsAutomaticallyOnlyOnFirstAppearance() {
+	func test_loadCommentsActions_runsAutomaticallyOnlyOnFirstAppearance() async {
 		let (sut, loader) = makeSUT()
 		XCTAssertEqual(loader.loadCommentsCallCount, 0, "Expected no loading requests before view appears")
 
@@ -50,120 +49,121 @@ class CommentsUIIntegrationTests: XCTestCase {
 		XCTAssertEqual(loader.loadCommentsCallCount, 1, "Expected no loading request the second time view appears")
 	}
 
-	func test_loadingCommentsIndicator_isVisibleWhileLoadingComments() {
+	func test_loadingCommentsIndicator_isVisibleWhileLoadingComments() async {
 		let (sut, loader) = makeSUT()
 
 		sut.simulateAppearance()
 		XCTAssertTrue(sut.isShowingLoadingIndicator, "Expected loading indicator once view appears")
 
-		loader.completeCommentsLoading(at: 0)
+		await loader.completeCommentsLoading(at: 0)
 		XCTAssertFalse(sut.isShowingLoadingIndicator, "Expected no loading indicator once loading completes successfully")
 
 		sut.simulateUserInitiatedReload()
 		XCTAssertTrue(sut.isShowingLoadingIndicator, "Expected loading indicator once user initiates a reload")
 
-		loader.completeCommentsLoadingWithError(at: 1)
+		await loader.completeCommentsLoadingWithError(at: 1)
 		XCTAssertFalse(sut.isShowingLoadingIndicator, "Expected no loading indicator once user initiated loading completes with error")
 	}
 
-	func test_loadCommentsCompletion_rendersSuccessfullyLoadedComments() {
+	func test_loadCommentsCompletion_rendersSuccessfullyLoadedComments() async {
 		let comment0 = makeComment(message: "a message", username: "a username")
 		let comment1 = makeComment(message: "another message", username: "another username")
 		let (sut, loader) = makeSUT()
 
 		sut.simulateAppearance()
 		assertThat(sut, isRendering: [ImageComment]())
 
-		loader.completeCommentsLoading(with: [comment0], at: 0)
+		await loader.completeCommentsLoading(with: [comment0], at: 0)
 		assertThat(sut, isRendering: [comment0])
 
 		sut.simulateUserInitiatedReload()
-		loader.completeCommentsLoading(with: [comment0, comment1], at: 1)
+		await loader.completeCommentsLoading(with: [comment0, comment1], at: 1)
 		assertThat(sut, isRendering: [comment0, comment1])
 	}
 
-	func test_loadCommentsCompletion_rendersSuccessfullyLoadedEmptyCommentsAfterNonEmptyComments() {
+	func test_loadCommentsCompletion_rendersSuccessfullyLoadedEmptyCommentsAfterNonEmptyComments() async {
 		let comment = makeComment()
 		let (sut, loader) = makeSUT()
 
 		sut.simulateAppearance()
-		loader.completeCommentsLoading(with: [comment], at: 0)
+		await loader.completeCommentsLoading(with: [comment], at: 0)
 		assertThat(sut, isRendering: [comment])
 
 		sut.simulateUserInitiatedReload()
-		loader.completeCommentsLoading(with: [], at: 1)
+		await loader.completeCommentsLoading(with: [], at: 1)
 		assertThat(sut, isRendering: [ImageComment]())
 	}
 
-	func test_loadCommentsCompletion_doesNotAlterCurrentRenderingStateOnError() {
+	func test_loadCommentsCompletion_doesNotAlterCurrentRenderingStateOnError() async {
 		let comment = makeComment()
 		let (sut, loader) = makeSUT()
 
 		sut.simulateAppearance()
-		loader.completeCommentsLoading(with: [comment], at: 0)
+		await loader.completeCommentsLoading(with: [comment], at: 0)
 		assertThat(sut, isRendering: [comment])
 
 		sut.simulateUserInitiatedReload()
-		loader.completeCommentsLoadingWithError(at: 1)
+		await loader.completeCommentsLoadingWithError(at: 1)
 		assertThat(sut, isRendering: [comment])
 	}
 
-	func test_loadCommentsCompletion_rendersErrorMessageOnErrorUntilNextReload() {
+	func test_loadCommentsCompletion_rendersErrorMessageOnErrorUntilNextReload() async {
 		let (sut, loader) = makeSUT()
 
 		sut.simulateAppearance()
 		XCTAssertEqual(sut.errorMessage, nil)
 
-		loader.completeCommentsLoadingWithError(at: 0)
+		await loader.completeCommentsLoadingWithError(at: 0)
 		XCTAssertEqual(sut.errorMessage, loadError)
 
 		sut.simulateUserInitiatedReload()
 		XCTAssertEqual(sut.errorMessage, nil)
 	}
 
-	func test_tapOnErrorView_hidesErrorMessage() {
+	func test_tapOnErrorView_hidesErrorMessage() async {
 		let (sut, loader) = makeSUT()
 
 		sut.simulateAppearance()
 		XCTAssertEqual(sut.errorMessage, nil)
 
-		loader.completeCommentsLoadingWithError(at: 0)
+		await loader.completeCommentsLoadingWithError(at: 0)
 		XCTAssertEqual(sut.errorMessage, loadError)
 
 		sut.simulateErrorViewTap()
 		XCTAssertEqual(sut.errorMessage, nil)
 	}
 
-	func test_deinit_cancelsRunningRequest() {
-		var cancelCallCount = 0
-		
+	func test_deinit_cancelsRunningRequest() async throws {
+		let loader = LoaderSpy<Void, [ImageComment]>()
 		var sut: ListViewController?
 
 		autoreleasepool {
-			sut = CommentsUIComposer.commentsComposedWith(commentsLoader: {
-				PassthroughSubject<[ImageComment], Error>()
-					.handleEvents(receiveCancel: {
-						cancelCallCount += 1
-					}).eraseToAnyPublisher()
-			})
-			
+			sut = CommentsUIComposer.commentsComposedWith(commentsLoader: loader.loadComments)
+
 			sut?.simulateAppearance()
 		}
 
-		XCTAssertEqual(cancelCallCount, 0)
+		XCTAssertEqual(loader.cancelledCommentsRequestsCount, 0)
 
 		sut = nil
+		let result = try await loader.result(at: 0)
 
-		XCTAssertEqual(cancelCallCount, 1)
+		XCTAssertEqual(result, .cancelled)
+		XCTAssertEqual(loader.cancelledCommentsRequestsCount, 1)
 	}
 
 	// MARK: - Helpers
 
-	private func makeSUT(file: StaticString = #filePath, line: UInt = #line) -> (sut: ListViewController, loader: LoaderSpy) {
-		let loader = LoaderSpy()
-		let sut = CommentsUIComposer.commentsComposedWith(commentsLoader: loader.loadPublisher)
+	private func makeSUT(file: StaticString = #filePath, line: UInt = #line) -> (sut: ListViewController, loader: LoaderSpy<Void, [ImageComment]>) {
+		let loader = LoaderSpy<Void, [ImageComment]>()
+		let sut = CommentsUIComposer.commentsComposedWith(commentsLoader: loader.loadComments)
 		trackForMemoryLeaks(loader, file: file, line: line)
 		trackForMemoryLeaks(sut, file: file, line: line)
+		
+		addTeardownBlock { [weak loader] in
+			try await loader?.cancelPendingRequests()
+		}
+
 		return (sut, loader)
 	}
 
@@ -182,28 +182,27 @@ class CommentsUIIntegrationTests: XCTestCase {
 			XCTAssertEqual(sut.commentUsername(at: index), comment.username, "username at \(index)", file: file, line: line)
 		}
 	}
+}
+
+private extension LoaderSpy where Param == Void, Resource == [ImageComment] {
+	var loadCommentsCallCount: Int {
+		return requests.count
+	}
 
-	private class LoaderSpy {
-		private var requests = [PassthroughSubject<[ImageComment], Error>]()
-		
-		var loadCommentsCallCount: Int {
-			return requests.count
-		}
-		
-		func loadPublisher() -> AnyPublisher<[ImageComment], Error> {
-			let publisher = PassthroughSubject<[ImageComment], Error>()
-			requests.append(publisher)
-			return publisher.eraseToAnyPublisher()
-		}
-		
-		func completeCommentsLoading(with comments: [ImageComment] = [], at index: Int = 0) {
-			requests[index].send(comments)
-			requests[index].send(completion: .finished)
-		}
-		
-		func completeCommentsLoadingWithError(at index: Int = 0) {
-			let error = NSError(domain: "an error", code: 0)
-			requests[index].send(completion: .failure(error))
-		}
+	var cancelledCommentsRequestsCount: Int {
+		requests.count { $0.result == .cancelled }
+	}
+	
+	func loadComments() async throws -> [ImageComment] {
+		try await load(())
+	}
+	
+	func completeCommentsLoading(with comments: [ImageComment] = [], at index: Int = 0) async {
+		await complete(with: comments, at: index)
+	}
+	
+	func completeCommentsLoadingWithError(at index: Int = 0) async {
+		let error = NSError(domain: "an error", code: 0)
+		await fail(with: error, at: index)
 	}
 }

EssentialFeed/EssentialFeed/Image Comments Feature/ImageComment.swift

@@ -4,7 +4,7 @@
 
 import Foundation
 
-public struct ImageComment: Equatable {
+public struct ImageComment: Equatable, Sendable {
 	public let id: UUID
 	public let message: String
 	public let createdAt: Date