chore: migrate HashtagViewModel to use `StatusFetchedResultsController`

Mastodon.xcodeproj/project.pbxproj

@@ -8,7 +8,6 @@
 
 /* Begin PBXBuildFile section */
 		0F1E2D0B2615C39400C38565 /* HashtagTimelineTitleView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0F1E2D0A2615C39400C38565 /* HashtagTimelineTitleView.swift */; };
-		0F1E2FE9261D7FD000C38565 /* StatusWithGapFetchResultController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0F1E2FE8261D7FD000C38565 /* StatusWithGapFetchResultController.swift */; };
 		0F2021FB2613262F000C64BF /* HashtagTimelineViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0F2021FA2613262F000C64BF /* HashtagTimelineViewController.swift */; };
 		0F202201261326E6000C64BF /* HashtagTimelineViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0F202200261326E6000C64BF /* HashtagTimelineViewModel.swift */; };
 		0F20220726134DA4000C64BF /* HashtagTimelineViewModel+Diffable.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0F20220626134DA4000C64BF /* HashtagTimelineViewModel+Diffable.swift */; };
@@ -357,7 +356,6 @@
 
 /* Begin PBXFileReference section */
 		0F1E2D0A2615C39400C38565 /* HashtagTimelineTitleView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = HashtagTimelineTitleView.swift; sourceTree = "<group>"; };
-		0F1E2FE8261D7FD000C38565 /* StatusWithGapFetchResultController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = StatusWithGapFetchResultController.swift; sourceTree = "<group>"; };
 		0F2021FA2613262F000C64BF /* HashtagTimelineViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = HashtagTimelineViewController.swift; sourceTree = "<group>"; };
 		0F202200261326E6000C64BF /* HashtagTimelineViewModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = HashtagTimelineViewModel.swift; sourceTree = "<group>"; };
 		0F20220626134DA4000C64BF /* HashtagTimelineViewModel+Diffable.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "HashtagTimelineViewModel+Diffable.swift"; sourceTree = "<group>"; };
@@ -1661,7 +1659,6 @@
 			isa = PBXGroup;
 			children = (
 				DBCBED1C26132E1A00B49291 /* StatusFetchedResultsController.swift */,
-				0F1E2FE8261D7FD000C38565 /* StatusWithGapFetchResultController.swift */,
 			);
 			path = FetchedResultsController;
 			sourceTree = "<group>";
@@ -2140,7 +2137,6 @@
 				DB71FD3C25F8A1C500512AE1 /* APIService+Persist+PersistCache.swift in Sources */,
 				2DA6055125F74407006356F9 /* AudioContainerViewModel.swift in Sources */,
 				0FB3D2FE25E4CB6400AAD544 /* PickServerTitleCell.swift in Sources */,
-				0F1E2FE9261D7FD000C38565 /* StatusWithGapFetchResultController.swift in Sources */,
 				DBCC3B7B261443AD0045B23D /* ViewController.swift in Sources */,
 				2D38F1DF25CD46A400561493 /* HomeTimelineViewController+StatusProvider.swift in Sources */,
 				2D206B9225F60EA700143C56 /* UIControl.swift in Sources */,

Mastodon/Diffiable/FetchedResultsController/StatusFetchedResultsController.swift

@@ -25,7 +25,7 @@ final class StatusFetchedResultsController: NSObject {
     // output
     let objectIDs = CurrentValueSubject<[NSManagedObjectID], Never>([])
     
-    init(managedObjectContext: NSManagedObjectContext, domain: String?, additionalTweetPredicate: NSPredicate) {
+    init(managedObjectContext: NSManagedObjectContext, domain: String?, additionalTweetPredicate: NSPredicate?) {
         self.domain.value = domain ?? ""
         self.fetchedResultsController = {
             let fetchRequest = Status.sortedFetchRequest
@@ -52,10 +52,11 @@ final class StatusFetchedResultsController: NSObject {
         .receive(on: DispatchQueue.main)
         .sink { [weak self] domain, ids in
             guard let self = self else { return }
-            self.fetchedResultsController.fetchRequest.predicate = NSCompoundPredicate(andPredicateWithSubpredicates: [
+            var predicates = [Status.predicate(domain: domain ?? "", ids: ids)]
-                Status.predicate(domain: domain ?? "", ids: ids),
+            if let additionalPredicate = additionalTweetPredicate {
-                additionalTweetPredicate
+                predicates.append(additionalPredicate)
-            ])
+            }
+            self.fetchedResultsController.fetchRequest.predicate = NSCompoundPredicate(andPredicateWithSubpredicates: predicates)
             do {
                 try self.fetchedResultsController.performFetch()
             } catch {

Mastodon/Diffiable/FetchedResultsController/StatusWithGapFetchResultController.swift

@@ -1,85 +0,0 @@
-//
-//  StatusWithGapFetchResultController.swift
-//  Mastodon
-//
-//  Created by BradGao on 2021/4/7.
-//
-
-import os.log
-import UIKit
-import Combine
-import CoreData
-import CoreDataStack
-import MastodonSDK
-
-class StatusWithGapFetchResultController: NSObject {
-    var disposeBag = Set<AnyCancellable>()
-    
-    let fetchedResultsController: NSFetchedResultsController<Status>
-
-    // input
-    let domain = CurrentValueSubject<String?, Never>(nil)
-    let statusIDs = CurrentValueSubject<[Mastodon.Entity.Status.ID], Never>([])
-    
-    var needLoadMiddleIndex: Int? = nil
-    
-    // output
-    let objectIDs = CurrentValueSubject<[NSManagedObjectID], Never>([])
-    
-    init(managedObjectContext: NSManagedObjectContext, domain: String?, additionalTweetPredicate: NSPredicate) {
-        self.domain.value = domain ?? ""
-        self.fetchedResultsController = {
-            let fetchRequest = Status.sortedFetchRequest
-            fetchRequest.returnsObjectsAsFaults = false
-            fetchRequest.fetchBatchSize = 20
-            let controller = NSFetchedResultsController(
-                fetchRequest: fetchRequest,
-                managedObjectContext: managedObjectContext,
-                sectionNameKeyPath: nil,
-                cacheName: nil
-            )
-
-            return controller
-        }()
-        super.init()
-        
-        fetchedResultsController.delegate = self
-        
-        Publishers.CombineLatest(
-            self.domain.removeDuplicates().eraseToAnyPublisher(),
-            self.statusIDs.removeDuplicates().eraseToAnyPublisher()
-        )
-        .receive(on: DispatchQueue.main)
-        .sink { [weak self] domain, ids in
-            guard let self = self else { return }
-            self.fetchedResultsController.fetchRequest.predicate = NSCompoundPredicate(andPredicateWithSubpredicates: [
-                Status.predicate(domain: domain ?? "", ids: ids),
-                additionalTweetPredicate
-            ])
-            do {
-                try self.fetchedResultsController.performFetch()
-            } catch {
-                assertionFailure(error.localizedDescription)
-            }
-        }
-        .store(in: &disposeBag)
-    }
-}
-
-// MARK: - NSFetchedResultsControllerDelegate
-extension StatusWithGapFetchResultController: NSFetchedResultsControllerDelegate {
-    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: NSDiffableDataSourceSnapshotReference) {
-        os_log("%{public}s[%{public}ld], %{public}s", ((#file as NSString).lastPathComponent), #line, #function)
-        
-        let indexes = statusIDs.value
-        let objects = fetchedResultsController.fetchedObjects ?? []
-        
-        let items: [NSManagedObjectID] = objects
-            .compactMap { object in
-                indexes.firstIndex(of: object.id).map { index in (index, object) }
-            }
-            .sorted { $0.0 < $1.0 }
-            .map { $0.1.objectID }
-        self.objectIDs.value = items
-    }
-}

Mastodon/Scene/HashtagTimeline/HashtagTimelineViewController.swift

@@ -108,6 +108,8 @@ extension HashtagTimelineViewController {
             }
             .store(in: &disposeBag)
         
+        
+
     }
     
     override func viewWillAppear(_ animated: Bool) {

Mastodon/Scene/HashtagTimeline/HashtagTimelineViewModel+Diffable.swift

@@ -33,14 +33,9 @@ extension HashtagTimelineViewModel {
     }
 }
 
-// MARK: - NSFetchedResultsControllerDelegate
+// MARK: - Compare old & new snapshots and generate new items
-extension HashtagTimelineViewModel: NSFetchedResultsControllerDelegate {
+extension HashtagTimelineViewModel {
-    
+    func generateStatusItems(newObjectIDs: [NSManagedObjectID]) {
-    func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
-        os_log("%{public}s[%{public}ld], %{public}s", ((#file as NSString).lastPathComponent), #line, #function)
-    }
-    
-    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: NSDiffableDataSourceSnapshotReference) {
         os_log("%{public}s[%{public}ld], %{public}s", ((#file as NSString).lastPathComponent), #line, #function)
         
         guard let tableView = self.tableView else { return }
@@ -48,12 +43,12 @@ extension HashtagTimelineViewModel: NSFetchedResultsControllerDelegate {
         
         guard let diffableDataSource = self.diffableDataSource else { return }
         
-        let parentManagedObjectContext = fetchedResultsController.managedObjectContext
+        let parentManagedObjectContext = fetchedResultsController.fetchedResultsController.managedObjectContext
         let managedObjectContext = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
         managedObjectContext.parent = parentManagedObjectContext
         
         let oldSnapshot = diffableDataSource.snapshot()
-        let snapshot = snapshot as NSDiffableDataSourceSnapshot<Int, NSManagedObjectID>
+//        let snapshot = snapshot as NSDiffableDataSourceSnapshot<Int, NSManagedObjectID>
         
         var oldSnapshotAttributeDict: [NSManagedObjectID : Item.StatusAttribute] = [:]
         for item in oldSnapshot.itemIdentifiers {
@@ -61,9 +56,7 @@ extension HashtagTimelineViewModel: NSFetchedResultsControllerDelegate {
             oldSnapshotAttributeDict[objectID] = attribute
         }
         
-        let statusItemList: [Item] = snapshot.itemIdentifiers.map {
+        let statusItemList: [Item] = newObjectIDs.map {
-            let status = managedObjectContext.object(with: $0) as! Status
-            
             let attribute = oldSnapshotAttributeDict[$0] ?? Item.StatusAttribute()
             return Item.status(objectID: $0, attribute: attribute)
         }
@@ -75,7 +68,7 @@ extension HashtagTimelineViewModel: NSFetchedResultsControllerDelegate {
         if let needLoadMiddleIndex = needLoadMiddleIndex, needLoadMiddleIndex < (statusItemList.count - 1) {
             // If yes, insert a `middleLoader` at the index
             var newItems = statusItemList
-            newItems.insert(.homeMiddleLoader(upperTimelineIndexAnchorObjectID: snapshot.itemIdentifiers[needLoadMiddleIndex]), at: (needLoadMiddleIndex + 1))
+            newItems.insert(.homeMiddleLoader(upperTimelineIndexAnchorObjectID: newObjectIDs[needLoadMiddleIndex]), at: (needLoadMiddleIndex + 1))
             newSnapshot.appendItems(newItems, toSection: .main)
         } else {
             newSnapshot.appendItems(statusItemList, toSection: .main)
@@ -112,6 +105,7 @@ extension HashtagTimelineViewModel: NSFetchedResultsControllerDelegate {
         newSnapshot: NSDiffableDataSourceSnapshot<StatusSection, T>
     ) -> Difference<T>? {
         guard oldSnapshot.numberOfItems != 0 else { return nil }
+        guard let item = oldSnapshot.itemIdentifiers.first as? Item, case Item.status = item else { return nil }
         
         let oldItemAtBeginning = oldSnapshot.itemIdentifiers(inSection: .main).first!
         
@@ -127,5 +121,4 @@ extension HashtagTimelineViewModel: NSFetchedResultsControllerDelegate {
         }
         return nil
     }
-    
 }

Mastodon/Scene/HashtagTimeline/HashtagTimelineViewModel+LoadLatestState.swift

@@ -73,18 +73,18 @@ extension HashtagTimelineViewModel.LoadLatestState {
                     // 1. is not empty
                     // 2. last status are not recorded
                     // Then we may have middle data to load
-                    if !viewModel.hashtagStatusIDList.isEmpty, let lastNewStatusID = newStatusIDList.last,
+                    var oldStatusIDs = viewModel.fetchedResultsController.statusIDs.value
-                       !viewModel.hashtagStatusIDList.contains(lastNewStatusID) {
+                    if !oldStatusIDs.isEmpty, let lastNewStatusID = newStatusIDList.last,
+                       !oldStatusIDs.contains(lastNewStatusID) {
                         viewModel.needLoadMiddleIndex = (newStatusIDList.count - 1)
                     } else {
                         viewModel.needLoadMiddleIndex = nil
                     }
                     
-                    viewModel.hashtagStatusIDList.insert(contentsOf: newStatusIDList, at: 0)
+                    oldStatusIDs.insert(contentsOf: newStatusIDList, at: 0)
-                    viewModel.hashtagStatusIDList.removeDuplicates()
+                    let newIDs = oldStatusIDs.removingDuplicates()
                     
-                    let newPredicate = Status.predicate(domain: activeMastodonAuthenticationBox.domain, ids: viewModel.hashtagStatusIDList)
+                    viewModel.fetchedResultsController.statusIDs.value = newIDs
-                    viewModel.timelinePredicate.send(newPredicate)
                 }
                 .store(in: &viewModel.disposeBag)
         }

Mastodon/Scene/HashtagTimeline/HashtagTimelineViewModel+LoadMiddleState.swift

@@ -54,11 +54,11 @@ extension HashtagTimelineViewModel.LoadMiddleState {
                 return
             }
             
-            guard let upperStatusObject = (viewModel.fetchedResultsController.fetchedObjects ?? []).first(where: { $0.objectID == upperStatusObjectID }) else {
+            guard let upperStatusObject = (viewModel.fetchedResultsController.fetchedResultsController.fetchedObjects ?? []).first(where: { $0.objectID == upperStatusObjectID }) else {
                 stateMachine.enter(Fail.self)
                 return
             }
-            let statusIDs = (viewModel.fetchedResultsController.fetchedObjects ?? []).compactMap { status in
+            let statusIDs = (viewModel.fetchedResultsController.fetchedResultsController.fetchedObjects ?? []).compactMap { status in
                 status.id
             }
 
@@ -86,27 +86,27 @@ extension HashtagTimelineViewModel.LoadMiddleState {
                     
                     let newStatusIDList = response.value.map { $0.id }
                     
-                    if let indexToInsert = viewModel.hashtagStatusIDList.firstIndex(of: maxID) {
+                    var oldStatusIDs = viewModel.fetchedResultsController.statusIDs.value
+                    if let indexToInsert = oldStatusIDs.firstIndex(of: maxID) {
                         // When response data:
                         // 1. is not empty
                         // 2. last status are not recorded
                         // Then we may have middle data to load
                         if let lastNewStatusID = newStatusIDList.last,
-                           !viewModel.hashtagStatusIDList.contains(lastNewStatusID) {
+                           !oldStatusIDs.contains(lastNewStatusID) {
                             viewModel.needLoadMiddleIndex = indexToInsert + newStatusIDList.count
                         } else {
                             viewModel.needLoadMiddleIndex = nil
                         }
-                        viewModel.hashtagStatusIDList.insert(contentsOf: newStatusIDList, at: indexToInsert + 1)
+                        oldStatusIDs.insert(contentsOf: newStatusIDList, at: indexToInsert + 1)
-                        viewModel.hashtagStatusIDList.removeDuplicates()
+                        oldStatusIDs.removeDuplicates()
                     } else {
                         // Only when the hashtagStatusIDList changes, we could not find the `loadMiddleState` index
                         // Then there is no need to set a `loadMiddleState` cell
                         viewModel.needLoadMiddleIndex = nil
                     }
                     
-                    let newPredicate = Status.predicate(domain: activeMastodonAuthenticationBox.domain, ids: viewModel.hashtagStatusIDList)
+                    viewModel.fetchedResultsController.statusIDs.value = oldStatusIDs
-                    viewModel.timelinePredicate.send(newPredicate)
                     
                 }
                 .store(in: &viewModel.disposeBag)

Mastodon/Scene/HashtagTimeline/HashtagTimelineViewModel+LoadOldestState.swift

@@ -29,7 +29,7 @@ extension HashtagTimelineViewModel.LoadOldestState {
     class Initial: HashtagTimelineViewModel.LoadOldestState {
         override func isValidNextState(_ stateClass: AnyClass) -> Bool {
             guard let viewModel = viewModel else { return false }
-            guard !(viewModel.fetchedResultsController.fetchedObjects ?? []).isEmpty else { return false }
+            guard !(viewModel.fetchedResultsController.fetchedResultsController.fetchedObjects ?? []).isEmpty else { return false }
             return stateClass == Loading.self
         }
     }
@@ -48,7 +48,7 @@ extension HashtagTimelineViewModel.LoadOldestState {
                 return
             }
             
-            guard let last = viewModel.fetchedResultsController.fetchedObjects?.last else {
+            guard let last = viewModel.fetchedResultsController.fetchedResultsController.fetchedObjects?.last else {
                 stateMachine.enter(Idle.self)
                 return
             }
@@ -79,10 +79,10 @@ extension HashtagTimelineViewModel.LoadOldestState {
                     } else {
                         stateMachine.enter(Idle.self)
                     }
-                    let newStatusIDList = statuses.map { $0.id }
+                    var newStatusIDs = viewModel.fetchedResultsController.statusIDs.value
-                    viewModel.hashtagStatusIDList.append(contentsOf: newStatusIDList)
+                    let fetchedStatusIDList = statuses.map { $0.id }
-                    let newPredicate = Status.predicate(domain: activeMastodonAuthenticationBox.domain, ids: viewModel.hashtagStatusIDList)
+                    newStatusIDs.append(contentsOf: fetchedStatusIDList)
-                    viewModel.timelinePredicate.send(newPredicate)
+                    viewModel.fetchedResultsController.statusIDs.value = newStatusIDs
                 }
                 .store(in: &viewModel.disposeBag)
         }

Mastodon/Scene/HashtagTimeline/HashtagTimelineViewModel.swift

@@ -19,12 +19,11 @@ final class HashtagTimelineViewModel: NSObject {
     
     var disposeBag = Set<AnyCancellable>()
     
-    var hashtagStatusIDList = [Mastodon.Entity.Status.ID]()
     var needLoadMiddleIndex: Int? = nil
     
     // input
     let context: AppContext
-    let fetchedResultsController: NSFetchedResultsController<Status>
+    let fetchedResultsController: StatusFetchedResultsController
     let isFetchingLatestTimeline = CurrentValueSubject<Bool, Never>(false)
     let timelinePredicate = CurrentValueSubject<NSPredicate?, Never>(nil)
     let hashtagEntity = CurrentValueSubject<Mastodon.Entity.Tag?, Never>(nil)
@@ -69,39 +68,14 @@ final class HashtagTimelineViewModel: NSObject {
     init(context: AppContext, hashTag: String) {
         self.context  = context
         self.hashTag = hashTag
-        self.fetchedResultsController = {
+        let activeMastodonAuthenticationBox = context.authenticationService.activeMastodonAuthenticationBox.value
-            let fetchRequest = Status.sortedFetchRequest
+        self.fetchedResultsController = StatusFetchedResultsController(managedObjectContext: context.managedObjectContext, domain: activeMastodonAuthenticationBox?.domain, additionalTweetPredicate: nil)
-            fetchRequest.returnsObjectsAsFaults = false
-            fetchRequest.fetchBatchSize = 20
-            let controller = NSFetchedResultsController(
-                fetchRequest: fetchRequest,
-                managedObjectContext: context.managedObjectContext,
-                sectionNameKeyPath: nil,
-                cacheName: nil
-            )
-
-            return controller
-        }()
         super.init()
         
-        fetchedResultsController.delegate = self
+        fetchedResultsController.objectIDs
-        
-        timelinePredicate
             .receive(on: DispatchQueue.main)
-            .compactMap { $0 }
+            .sink { [weak self] objectIds in
-            .sink { [weak self] predicate in
+                self?.generateStatusItems(newObjectIDs: objectIds)
-                guard let self = self else { return }
-                self.fetchedResultsController.fetchRequest.predicate = predicate
-                do {
-                    self.diffableDataSource?.defaultRowAnimation = .fade
-                    try self.fetchedResultsController.performFetch()
-                    DispatchQueue.main.asyncAfter(deadline: .now() + 3) { [weak self] in
-                        guard let self = self else { return }
-                        self.diffableDataSource?.defaultRowAnimation = .automatic
-                    }
-                } catch {
-                    assertionFailure(error.localizedDescription)
-                }
             }
             .store(in: &disposeBag)
     }