vector-im/element-x-ios/issues/53 - Adopt MainActors, dispatch heavy operations do detached tasks and ensure combine publisher call back on the right queue

ElementX/Sources/Other/Coordinator.swift

@@ -19,6 +19,7 @@ import UIKit
 /// Protocol describing a [Coordinator](http://khanlou.com/2015/10/coordinators-redux/).
 /// Coordinators are the objects which control the navigation flow of the application.
 /// It helps to isolate and reuse view controllers and pass dependencies down the navigation hierarchy.
+@MainActor
 protocol Coordinator: AnyObject {
     
     /// Starts job of the coordinator.

ElementX/Sources/Other/Routers/NavigationRouterStoreProtocol.swift

@@ -17,6 +17,7 @@
 import UIKit
 
 /// `NavigationRouterStoreProtocol` describes a structure that enables to get a NavigationRouter from a UINavigationController instance.
+@MainActor
 protocol NavigationRouterStoreProtocol {
     
     /// Gets the existing navigation router for the supplied controller, creating a new one if it doesn't yet exist.

ElementX/Sources/Other/Routers/NavigationRouterType.swift

@@ -18,6 +18,7 @@ import UIKit
 
 /// Protocol describing a router that wraps a UINavigationController and add convenient completion handlers. Completions are called when a Presentable is removed.
 /// Routers are used to be passed between coordinators. They handles only `physical` navigation.
+@MainActor
 protocol NavigationRouterType: AnyObject, Presentable {
 
     /// Present modally a view controller on the navigation controller

ElementX/Sources/Other/Routers/Presentable.swift

@@ -17,6 +17,7 @@
 import UIKit
 
 /// Protocol used to pass UIViewControllers to routers
+@MainActor
 protocol Presentable {
     func toPresentable() -> UIViewController
 }

ElementX/Sources/Other/Routers/RootRouterType.swift

@@ -18,6 +18,7 @@ import UIKit
 
 /// Protocol describing a router that wraps the root navigation of the application.
 /// Routers are used to be passed between coordinators. They handles only `physical` navigation.
+@MainActor
 protocol RootRouterType: AnyObject {          
     
     /// Update the root view controller

ElementX/Sources/Other/SwiftUI/ViewModel/StateStoreViewModel.swift

@@ -30,6 +30,7 @@ import Combine
 /// It provides a nice layer of consistency and also safety. As we are not passing the `ViewModel` to the view directly, shortcuts/hacks
 /// can't be made into the `ViewModel`.
 @dynamicMemberLookup
+@MainActor
 class ViewModelContext<ViewState: BindableState, ViewAction>: ObservableObject {
     // MARK: - Properties
 
@@ -70,6 +71,7 @@ class ViewModelContext<ViewState: BindableState, ViewAction>: ObservableObject {
 /// a specific portion of state that can be safely bound to.
 /// If we decide to add more features to our state management (like doing state processing off the main thread)
 /// we can do it in this centralised place.
+@MainActor
 class StateStoreViewModel<State: BindableState, ViewAction> {
 
     typealias Context = ViewModelContext<State, ViewAction>

ElementX/Sources/Screens/HomeScreen/HomeScreenCoordinator.swift

@@ -85,19 +85,15 @@ final class HomeScreenCoordinator: Coordinator, Presentable {
         Task {
             if case let .success(userAvatarURL) = await parameters.userSession.loadUserAvatarURL() {
                 if case let .success(avatar) = await parameters.mediaProvider.loadImageFromURL(userAvatarURL) {
-                    await MainActor.run {
                     self.viewModel.updateWithUserAvatar(avatar)
                 }
             }
-            }
             
             if case let .success(userDisplayName) = await parameters.userSession.loadUserDisplayName() {
-                await MainActor.run {
                 self.viewModel.updateWithUserDisplayName(userDisplayName)
             }
         }
     }
-    }
     
     // MARK: - Public
     func start() {

ElementX/Sources/Screens/HomeScreen/HomeScreenViewModel.swift

@@ -47,11 +47,11 @@ class HomeScreenViewModel: HomeScreenViewModelType, HomeScreenViewModelProtocol
     override func process(viewAction: HomeScreenViewAction) {
         switch viewAction {
         case .logout:
-            self.completion?(.logout)
+            completion?(.logout)
         case .loadRoomData(let roomIdentifier):
-            self.loadRoomDataForIdentifier(roomIdentifier)
+            loadRoomDataForIdentifier(roomIdentifier)
         case .selectRoom(let roomIdentifier):
-            self.completion?(.selectRoom(roomIdentifier: roomIdentifier))
+            completion?(.selectRoom(roomIdentifier: roomIdentifier))
         }
     }
     

ElementX/Sources/Screens/HomeScreen/HomeScreenViewModelProtocol.swift

@@ -17,6 +17,7 @@
 import Foundation
 import UIKit
 
+@MainActor
 protocol HomeScreenViewModelProtocol {
     var completion: ((HomeScreenViewModelResult) -> Void)? { get set }
     

ElementX/Sources/Screens/LoginScreen/LoginScreenViewModelProtocol.swift

@@ -16,6 +16,7 @@
 
 import Foundation
 
+@MainActor
 protocol LoginScreenViewModelProtocol {
     var completion: ((LoginScreenViewModelResult) -> Void)? { get set }
     var context: LoginScreenViewModelType.Context { get }

ElementX/Sources/Screens/RoomScreen/RoomScreenModels.swift

@@ -39,7 +39,7 @@ struct RoomScreenViewState: BindableState {
     var isBackPaginating = false
     var bindings: RoomScreenViewStateBindings
     
-    var contextMenuBuilder: ((_ itemId: String) -> TimelineItemContextMenu)?
+    var contextMenuBuilder: (@MainActor (_ itemId: String) -> TimelineItemContextMenu)?
     
     var sendButtonDisabled: Bool {
         bindings.composerText.count == 0

ElementX/Sources/Screens/RoomScreen/RoomScreenViewModel.swift

@@ -67,16 +67,12 @@ class RoomScreenViewModel: RoomScreenViewModelType, RoomScreenViewModelProtocol
         Task {
             switch viewAction {
             case .loadPreviousPage:
-                await MainActor.run {
                 state.isBackPaginating = true
-                }
                 
                 switch await timelineController.paginateBackwards(Constants.backPaginationPageSize) {
                 default:
-                    await MainActor.run {
                     state.isBackPaginating = false
                 }
-                }
                 
             case .itemAppeared(let id):
                 await timelineController.processItemAppearance(id)
@@ -90,13 +86,10 @@ class RoomScreenViewModel: RoomScreenViewModelType, RoomScreenViewModelProtocol
                 }
                 
                 await timelineController.sendMessage(state.bindings.composerText)
-                
-                await MainActor.run {
                 state.bindings.composerText = ""
             }
         }
     }
-    }
     
     // MARK: - Private
     

ElementX/Sources/Screens/RoomScreen/RoomScreenViewModelProtocol.swift

@@ -16,6 +16,7 @@
 
 import Foundation
 
+@MainActor
 protocol RoomScreenViewModelProtocol {
     var context: RoomScreenViewModelType.Context { get }
 }

ElementX/Sources/Services/Authentication/AuthenticationCoordinator.swift

@@ -14,6 +14,7 @@ enum AuthenticationCoordinatorError: Error {
     case failedSettingUpSession
 }
 
+@MainActor
 protocol AuthenticationCoordinatorDelegate: AnyObject {
     
     func authenticationCoordinatorDidStartLoading(_ authenticationCoordinator: AuthenticationCoordinator)

ElementX/Sources/Services/Authentication/UserSession.swift

@@ -27,12 +27,13 @@ private class WeakUserSessionWrapper: ClientDelegate {
         self.userSession = userSession
     }
     
-    func didReceiveSyncUpdate() {
+    @MainActor func didReceiveSyncUpdate() {
         self.userSession?.didReceiveSyncUpdate()
     }
 }
 
-class UserSession: ClientDelegate {
+@MainActor
+class UserSession {
     
     private let client: Client
     
@@ -74,26 +75,26 @@ class UserSession: ClientDelegate {
     }
     
     func loadUserDisplayName() async -> Result<String, UserSessionError> {
-        await withCheckedContinuation { continuation in
+        await Task.detached { () -> Result<String, UserSessionError> in
             do {
                 let displayName = try self.client.displayName()
-                continuation.resume(returning: .success(displayName))
+                return .success(displayName)
             } catch {
-                continuation.resume(returning: .failure(.failedRetrievingDisplayName))
+                return .failure(.failedRetrievingDisplayName)
             }
             
-        }
+        }.value
     }
         
     func loadUserAvatarURL() async -> Result<String, UserSessionError> {
-        await withCheckedContinuation { continuation in
+        await Task.detached { () -> Result<String, UserSessionError> in
             do {
                 let avatarURL = try self.client.avatarUrl()
-                continuation.resume(returning: .success(avatarURL))
+                return .success(avatarURL)
             } catch {
-                continuation.resume(returning: .failure(.failedRetrievingDisplayName))
+                return .failure(.failedRetrievingDisplayName)
-            }
             }
+        }.value
     }
     
     // MARK: ClientDelegate
@@ -101,8 +102,8 @@ class UserSession: ClientDelegate {
     func didReceiveSyncUpdate() {
         Benchmark.logElapsedDurationForIdentifier("ClientSync", message: "Received sync update")
         
-        Task {
+        Task.detached {
-            await updateRooms()
+            await self.updateRooms()
         }
     }
     

ElementX/Sources/Services/Media/MediaProvider.swift

@@ -46,33 +46,33 @@ struct MediaProvider: MediaProviderProtocol {
             return .success(image)
         }
         
-        return await withCheckedContinuation { continuation in
+        let cachedImageLoadResult = await withCheckedContinuation({ continuation in
             imageCache.retrieveImage(forKey: source.underlyingSource.url()) { result in
-                if case let .success(cacheResult) = result,
+                continuation.resume(returning: result)
+            }
+        })
+            
+        if case let .success(cacheResult) = cachedImageLoadResult,
            let image = cacheResult.image {
-                    continuation.resume(returning: .success(image))
+            return .success(image)
-                    return
         }
         
-                processingQueue.async {
+        return await Task.detached { () -> Result<UIImage, MediaProviderError> in
             do {
                 let imageData = try client.getMediaContent(source: source.underlyingSource)
                 
                 guard let image = UIImage(data: Data(bytes: imageData, count: imageData.count)) else {
                     MXLog.error("Invalid image data")
-                            continuation.resume(returning: .failure(.invalidImageData))
+                    return .failure(.invalidImageData)
-                            return
                 }
                 
                 imageCache.store(image, forKey: source.underlyingSource.url())
                 
-                        continuation.resume(returning: .success(image))
+                return .success(image)
             } catch {
                 MXLog.error("Failed retrieving image with error: \(error)")
-                        continuation.resume(returning: .failure(.failedRetrievingImage))
+                return .failure(.failedRetrievingImage)
-                    }
-                }
-            }
             }
+        }.value
     }
 }

ElementX/Sources/Services/Media/MediaProviderProtocol.swift

@@ -14,6 +14,7 @@ enum MediaProviderError: Error {
     case invalidImageData
 }
 
+@MainActor
 protocol MediaProviderProtocol {
     func imageFromSource(_ source: MediaSource?) -> UIImage?
     

ElementX/Sources/Services/Room/Members/MemberDetailProviderManager.swift

@@ -8,6 +8,7 @@
 
 import Foundation
 
+@MainActor
 class MemberDetailProviderManager {
     
     private var memberDetailProviders: [String: MemberDetailProviderProtocol] = [:]

ElementX/Sources/Services/Room/Members/MemberDetailsProviderProtocol.swift

@@ -14,6 +14,7 @@ enum MemberDetailProviderError: Error {
     case failedRetrievingUserDisplayName
 }
 
+@MainActor
 protocol MemberDetailProviderProtocol {
     func avatarURLForUserId(_ userId: String) -> String?
     func loadAvatarURLForUserId(_ userId: String) async -> Result<String?, MemberDetailProviderError>

ElementX/Sources/Services/Room/RoomProxy.swift

@@ -44,10 +44,8 @@ class RoomProxy: RoomProxyProtocol {
         
         room.setDelegate(delegate: WeakRoomProxyWrapper(roomProxy: self))
         
-        Task {
         backwardStream = room.startLiveEventListener()
     }
-    }
     
     var id: String {
         room.id()
@@ -86,50 +84,48 @@ class RoomProxy: RoomProxyProtocol {
     }
     
     func loadAvatarURLForUserId(_ userId: String) async -> Result<String?, RoomProxyError> {
-        await withCheckedContinuation({ continuation in
+        await Task.detached { () -> Result<String?, RoomProxyError> in
             do {
                 let avatarURL = try self.room.memberAvatarUrl(userId: userId)
-                continuation.resume(returning: .success(avatarURL))
+                return .success(avatarURL)
             } catch {
-                continuation.resume(returning: .failure(.failedRetrievingMemberAvatarURL))
+                return .failure(.failedRetrievingMemberAvatarURL)
             }
-        })
+        }.value
     }
     
     func loadDisplayNameForUserId(_ userId: String) async -> Result<String?, RoomProxyError> {
-        await withCheckedContinuation({ continuation in
+        await Task.detached { () -> Result<String?, RoomProxyError> in
             do {
                 let displayName = try self.room.memberDisplayName(userId: userId)
-                continuation.resume(returning: .success(displayName))
+                return .success(displayName)
             } catch {
-                continuation.resume(returning: .failure(.failedRetrievingMemberDisplayName))
+                return .failure(.failedRetrievingMemberDisplayName)
             }
-        })
+        }.value
     }
         
     func loadDisplayName() async -> Result<String, RoomProxyError> {
-        await withCheckedContinuation({ continuation in
+        await Task.detached { () -> Result<String, RoomProxyError> in
-            if let displayName = displayName {
+            if let displayName = self.displayName {
-                continuation.resume(returning: .success(displayName))
+                return .success(displayName)
-                return
             }
             
             do {
                 let displayName = try self.room.displayName()
                 self.displayName = displayName
                 
-                continuation.resume(returning: .success(displayName))
+                return .success(displayName)
             } catch {
-                continuation.resume(returning: .failure(.failedRetrievingDisplayName))
+                return .failure(.failedRetrievingDisplayName)
             }
-        })
+        }.value
     }
     
     func paginateBackwards(count: UInt) async -> Result<Void, RoomProxyError> {
-        await withCheckedContinuation { continuation in
+        await Task.detached { () -> Result<Void, RoomProxyError> in
             guard let backwardStream = self.backwardStream else {
-                continuation.resume(returning: .failure(.backwardStreamNotAvailable))
+                return .failure(RoomProxyError.backwardStreamNotAvailable)
-                return
             }
 
             Benchmark.startTrackingForIdentifier("BackPagination \(self.id)", message: "Backpaginating \(count) message(s) in room \(self.id)")
@@ -142,22 +138,22 @@ class RoomProxy: RoomProxyProtocol {
 
             self.messages.insert(contentsOf: messages, at: 0)
             
-            continuation.resume(returning: .success(()))
+            return .success(())
-        }
+        }.value
     }
     
     func sendMessage(_ message: String) async -> Result<Void, RoomProxyError> {
         let messageContent = messageEventContentFromMarkdown(md: message)
         let transactionId = genTransactionId()
         
-        return await withCheckedContinuation { continuation in
+        return await Task(priority: .high) { () -> Result<Void, RoomProxyError> in
             do {
                 try self.room.send(msg: messageContent, txnId: transactionId)
-                continuation.resume(returning: .success(()))
+                return .success(())
             } catch {
-                continuation.resume(returning: .failure(.failedSendingMessage))
+                return .failure(.failedSendingMessage)
-            }
             }
+        }.value
     }
     
     // MARK: - Private

ElementX/Sources/Services/Room/RoomSummary/EventBriefFactoryProtocol.swift

@@ -8,6 +8,7 @@
 
 import Foundation
 
+@MainActor
 protocol EventBriefFactoryProtocol {
     func eventBriefForMessage(_ message: RoomMessageProtocol?) async -> EventBrief?
 }

ElementX/Sources/Services/Room/RoomSummary/RoomSummary.swift

@@ -98,13 +98,13 @@ class RoomSummary: RoomSummaryProtocol {
         }
         
         await withTaskGroup(of: Void.self) { group in
-            group.addTask {
+            group.addTask(priority: .medium) {
                 await self.loadDisplayName()
             }
-            group.addTask {
+            group.addTask(priority: .medium) {
                 await self.loadAvatar()
             }
-            group.addTask {
+            group.addTask(priority: .medium) {
                 await self.loadLastMessage()
             }
         }

ElementX/Sources/Services/Room/RoomSummary/RoomSummaryProtocol.swift

@@ -13,6 +13,7 @@ enum RoomSummaryCallback {
     case updatedData
 }
 
+@MainActor
 protocol RoomSummaryProtocol {
     var id: String { get }
     var name: String? { get }

ElementX/Sources/Services/Timeline/RoomTimelineController.swift

@@ -31,7 +31,10 @@ class RoomTimelineController: RoomTimelineControllerProtocol {
         self.mediaProvider = mediaProvider
         self.memberDetailProvider = memberDetailProvider
         
-        self.timelineProvider.callbacks.sink { [weak self] callback in
+        self.timelineProvider
+            .callbacks
+            .receive(on: DispatchQueue.main)
+            .sink { [weak self] callback in
             guard let self = self else { return }
             
             switch callback {

ElementX/Sources/Services/Timeline/RoomTimelineControllerProtocol.swift

@@ -18,6 +18,7 @@ enum RoomTimelineControllerError: Error {
     case generic
 }
 
+@MainActor
 protocol RoomTimelineControllerProtocol {
     var timelineItems: [RoomTimelineItemProtocol] { get }
     var callbacks: PassthroughSubject<RoomTimelineControllerCallback, Never> { get }

ElementX/Sources/Services/Timeline/RoomTimelineProviderProtocol.swift

@@ -18,6 +18,7 @@ enum RoomTimelineProviderError: Error {
     case generic
 }
 
+@MainActor
 protocol RoomTimelineProviderProtocol {
     var callbacks: PassthroughSubject<RoomTimelineProviderCallback, Never> { get }
     

ElementX/Sources/Services/Timeline/TimelineItems/RoomTimelineItemFactory.swift

@@ -9,6 +9,7 @@
 import Foundation
 import UIKit
 
+@MainActor
 struct RoomTimelineItemFactory {
     private let mediaProvider: MediaProviderProtocol
     private let memberDetailProvider: MemberDetailProviderProtocol

ElementX/Sources/Services/Timeline/TimelineItems/RoomTimelineViewFactory.swift

@@ -8,6 +8,7 @@
 
 import Foundation
 
+@MainActor
 struct RoomTimelineViewFactory {
     func buildTimelineViewFor(_ timelineItem: RoomTimelineItemProtocol) -> RoomTimelineViewProvider {
         switch timelineItem {

Tools/Scripts/Templates/SimpleScreenExample/ElementX/TemplateSimpleScreenViewModelProtocol.swift

@@ -16,6 +16,7 @@
 
 import Foundation
 
+@MainActor
 protocol TemplateSimpleScreenViewModelProtocol {
     var completion: ((TemplateSimpleScreenViewModelResult) -> Void)? { get set }
     var context: TemplateSimpleScreenViewModelType.Context { get }