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* Add cell heights cache so that new contentSize calculation is more precise * Remove `_messageListDiffingEnabled` flag and diffable data source implementation * WIP DifferenceKit * Move DiffKit logic to Message List only * Improve performance by using ChatMessage directly instead of mapping always to DiffChatMessage * Improve performance of the message list by skipping channel list updates * Disable animations when loading new messages Since the this was actually not causing the messages to jump * Fix not loading previous messages when there are skipped messages * Add `ListChange` helpers * WIP Skipping Messages * Move the skipping logic to the message list view * Improve the performance of Message Content Equality * Fix Giphy not updating the UI when moved from original position * Add code docs to cell height cache + channel list skip rendering * Add comments explaining CATransaction in DiffKit reload * Update CHANGELOG.md * Update documentation of our dependencies * When skipping messages, only skip insertions, not all updates * Improve the readability of skipping messages * Always store the original messages from the data source to avoid data inconsistencies * Provide comments for the new introduced methods * Add Sentry dependency to DemoApp and remove it from StreamChat * Properly add DifferenceKit dependency * Ignore third party dependencies when formatting code with SwiftFormat * Add required declarations changes to DiffKit dependency Also adds a function to make the removePublicDeclarations.sh more readable * Undo changes on SwiftyMarkdown done by our SwiftFormat * Add missing required declaration changes to DiffKit Source files * Move DiffKit logic to the correct files * Add missing message id comparison in ChatMessage Content Equality * Fix crash when message from same user but with difference device is inserted while skipping messages This caused some data concurrency issues because a lot of data updates are triggered. In order to avoid this reloadData() is much more safe. * Remove willUpdateMessages events since it is actually not needed * Fix message cell layout options not being correctly calculated It was using the data controller directly, instead of the data source messages * Make sure to use the messages from the data source in ChatThreadVC * Intial POC for background mappings * Working POC for Background Mapping list & channel * Remove leftovers * Make messages list work * Move to custom queue * Bring back some non failing parsing * Force enable flags * Keep certain properties as lazy * Unify flags under _isBackgroundMappingEnabled * Add force flag to CoreDataLazy * Add safety to ListDatabaseObserverWrapper * Use environment in Channel List * Address small bits * Fix missing reset * Remove warnings * Use custom assertions * Add tets for BackgroundListDatabaseObserver * Add CoreDataLazy tests for _isBackgroundMappingEnabled * Add tests for LazyCachedMapCollection Co-authored-by: Nuno Vieira <nuno.fcvieira93@gmail.com>
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297
Sources/StreamChat/Controllers/BackgroundListDatabaseObserver.swift
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,297 @@ | ||
| // | ||
| // Copyright © 2022 Stream.io Inc. All rights reserved. | ||
| // | ||
|
|
||
| import CoreData | ||
| import Foundation | ||
|
|
||
| class ListDatabaseObserverWrapper<Item, DTO: NSManagedObject> { | ||
| private var foreground: ListDatabaseObserver<Item, DTO>? | ||
| private var background: BackgroundListDatabaseObserver<Item, DTO>? | ||
| let isBackground: Bool | ||
|
|
||
| var items: LazyCachedMapCollection<Item> { | ||
| if isBackground, let background = background { | ||
| return background.items | ||
| } else if let foreground = foreground { | ||
| return foreground.items | ||
| } else { | ||
| log.assertionFailure("Should have foreground or background observer") | ||
| return [] | ||
| } | ||
| } | ||
|
|
||
| /// Called with the aggregated changes after the internal `NSFetchResultsController` calls `controllerWillChangeContent` | ||
| /// on its delegate. | ||
| var onWillChange: (() -> Void)? { | ||
| didSet { | ||
| if isBackground { | ||
| background?.onWillChange = onWillChange | ||
| } else { | ||
| foreground?.onWillChange = onWillChange | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /// Called with the aggregated changes after the internal `NSFetchResultsController` calls `controllerDidChangeContent` | ||
| /// on its delegate. | ||
| var onDidChange: (([ListChange<Item>]) -> Void)? { | ||
| didSet { | ||
| if isBackground { | ||
| background?.onDidChange = onDidChange | ||
| } else { | ||
| foreground?.onChange = onDidChange | ||
| } | ||
| } | ||
| } | ||
|
|
||
| init( | ||
| isBackground: Bool, | ||
| database: DatabaseContainer, | ||
| fetchRequest: NSFetchRequest<DTO>, | ||
| itemCreator: @escaping (DTO) throws -> Item, | ||
| fetchedResultsControllerType: NSFetchedResultsController<DTO>.Type = NSFetchedResultsController<DTO>.self | ||
| ) { | ||
| self.isBackground = isBackground | ||
| if isBackground { | ||
| background = BackgroundListDatabaseObserver( | ||
| context: database.backgroundReadOnlyContext, | ||
| fetchRequest: fetchRequest, | ||
| itemCreator: itemCreator, | ||
| fetchedResultsControllerType: fetchedResultsControllerType | ||
| ) | ||
| } else { | ||
| foreground = ListDatabaseObserver( | ||
| context: database.viewContext, | ||
| fetchRequest: fetchRequest, | ||
| itemCreator: itemCreator, | ||
| fetchedResultsControllerType: fetchedResultsControllerType | ||
| ) | ||
| } | ||
| } | ||
|
|
||
| func startObserving() throws { | ||
| if isBackground, let background = background { | ||
| try background.startObserving() | ||
| } else if let foreground = foreground { | ||
| try foreground.startObserving() | ||
| } else { | ||
| log.assertionFailure("Should have foreground or background observer") | ||
| } | ||
| } | ||
| } | ||
|
|
||
| class BackgroundListDatabaseObserver<Item, DTO: NSManagedObject> { | ||
| /// Called with the aggregated changes after the internal `NSFetchResultsController` calls `controllerWillChangeContent` | ||
| /// on its delegate. | ||
| var onWillChange: (() -> Void)? | ||
|
|
||
| /// Called with the aggregated changes after the internal `NSFetchResultsController` calls `controllerDidChangeContent` | ||
| /// on its delegate. | ||
| var onDidChange: (([ListChange<Item>]) -> Void)? | ||
|
|
||
| /// Used to convert the `DTO`s to the resulting `Item`s. | ||
| private let itemCreator: (DTO) throws -> Item | ||
|
|
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| /// Used for observing the changes in the DB. | ||
| let frc: NSFetchedResultsController<DTO> | ||
|
|
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| /// Acts like the `NSFetchedResultsController`'s delegate and aggregates the reported changes into easily consumable form. | ||
| let changeAggregator: ListChangeAggregator<DTO, Item> | ||
|
|
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| /// When called, release the notification observers | ||
| private(set) var releaseNotificationObservers: (() -> Void)? | ||
|
|
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| private let queue = DispatchQueue(label: "io.getstream.list-database-observer", qos: .userInitiated) | ||
|
|
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| private var _items: [Item] = [] | ||
| var items: LazyCachedMapCollection<Item> { | ||
| queue.sync { LazyCachedMapCollection(source: _items, map: { $0 }) } | ||
| } | ||
|
|
||
| private var _isInitialized: Bool = false | ||
| private var isInitialized: Bool { | ||
| get { | ||
| queue.sync { _isInitialized } | ||
| } | ||
| set { | ||
| queue.async(flags: .barrier) { | ||
| self._isInitialized = newValue | ||
| } | ||
| } | ||
| } | ||
|
|
||
| deinit { | ||
| releaseNotificationObservers?() | ||
| } | ||
|
|
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| /// Creates a new `ListObserver`. | ||
| /// | ||
| /// Please note that no updates are reported until you call `startUpdating`. | ||
| /// | ||
| /// - Important: ⚠️ Because the observer uses `NSFetchedResultsController` to observe the entity in the DB, it's required | ||
| /// that the provided `fetchRequest` has at lease one `NSSortDescriptor` specified. | ||
| /// | ||
| /// - Parameters: | ||
| /// - fetchRequest: The `NSFetchRequest` that specifies the elements of the list. | ||
| /// - context: The `NSManagedObjectContext` the observer observes. | ||
| /// - fetchedResultsControllerType: The `NSFetchedResultsController` subclass the observe uses to create its FRC. You can | ||
| /// inject your custom subclass if needed, i.e. when testing. | ||
| init( | ||
| context: NSManagedObjectContext, | ||
| fetchRequest: NSFetchRequest<DTO>, | ||
| itemCreator: @escaping (DTO) throws -> Item, | ||
| fetchedResultsControllerType: NSFetchedResultsController<DTO>.Type = NSFetchedResultsController<DTO>.self | ||
| ) { | ||
| self.itemCreator = itemCreator | ||
| changeAggregator = ListChangeAggregator<DTO, Item>(itemCreator: itemCreator) | ||
| frc = fetchedResultsControllerType.init( | ||
| fetchRequest: fetchRequest, | ||
| managedObjectContext: context, | ||
| sectionNameKeyPath: nil, | ||
| cacheName: nil | ||
| ) | ||
|
|
||
| changeAggregator.onWillChange = { [weak self] in | ||
| self?.notifyWillChange() | ||
| } | ||
|
|
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| changeAggregator.onDidChange = { [weak self] changes in | ||
| self?.processItems(changes) | ||
| } | ||
|
|
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| listenForRemoveAllDataNotifications() | ||
| } | ||
|
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| /// Starts observing the changes in the database. The current items in the list are synchronously available in the | ||
| /// `item` variable, after this function returns. | ||
| /// | ||
| /// - Throws: An error if the provided fetch request fails. | ||
| func startObserving() throws { | ||
| guard !isInitialized else { return } | ||
| isInitialized = true | ||
|
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| onWillChange?() | ||
|
|
||
| do { | ||
| try frc.performFetch() | ||
| } catch { | ||
| log.error("Failed to start observing database: \(error). This is an internal error.") | ||
| throw error | ||
| } | ||
|
|
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| frc.delegate = changeAggregator | ||
|
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| processItems() | ||
| } | ||
|
|
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| private func notifyWillChange() { | ||
| DispatchQueue.main.async { [weak self] in | ||
| self?.onWillChange?() | ||
| } | ||
| } | ||
|
|
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| private func notifyDidChange(changes: [ListChange<Item>]) { | ||
| DispatchQueue.main.async { [weak self] in | ||
| self?.onDidChange?(changes) | ||
| } | ||
| } | ||
|
|
||
| private func mapItems(completion: @escaping ([Item]) -> Void) { | ||
| let objects = frc.fetchedObjects ?? [] | ||
| let context = frc.managedObjectContext | ||
|
|
||
| var items = [Item?](repeating: nil, count: objects.count) | ||
|
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| let group = DispatchGroup() | ||
| for (i, dto) in objects.enumerated() { | ||
| group.enter() | ||
| context.perform { [weak self] in | ||
| items[i] = try? self?.itemCreator(dto) | ||
| group.leave() | ||
| } | ||
| } | ||
|
|
||
| group.notify(queue: queue) { | ||
| completion(items.compactMap { $0 }) | ||
| } | ||
| } | ||
|
|
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| private func processItems(_ changes: [ListChange<Item>] = []) { | ||
| mapItems { [weak self] items in | ||
| self?._items = items | ||
| self?.notifyDidChange(changes: changes) | ||
| } | ||
| } | ||
|
|
||
| /// Listens for `Will/DidRemoveAllData` notifications from the context and simulates the callback when the notifications | ||
| /// are received. | ||
| private func listenForRemoveAllDataNotifications() { | ||
| let notificationCenter = NotificationCenter.default | ||
| let context = frc.managedObjectContext | ||
|
|
||
| // When `WillRemoveAllDataNotification` is received, we need to simulate the callback from change observer, like all | ||
| // existing entities are being removed. At this point, these entities still existing in the context, and it's safe to | ||
| // access and serialize them. | ||
| let willRemoveAllDataNotificationObserver = notificationCenter.addObserver( | ||
| forName: DatabaseContainer.WillRemoveAllDataNotification, | ||
| object: context, | ||
| queue: .main | ||
| ) { [weak self] _ in | ||
| // Technically, this should rather be `unowned`, however, `deinit` is not always called on the main thread which can | ||
| // cause a race condition when the notification observers are not removed at the right time. | ||
| guard let self = self else { return } | ||
| guard let fetchResultsController = self.frc as? NSFetchedResultsController<NSFetchRequestResult> else { return } | ||
|
|
||
| // Simulate ChangeObserver callbacks like all data are being removed | ||
| self.changeAggregator.controllerWillChangeContent(fetchResultsController) | ||
|
|
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| self.frc.fetchedObjects?.enumerated().forEach { index, item in | ||
| self.changeAggregator.controller( | ||
| fetchResultsController, | ||
| didChange: item, | ||
| at: IndexPath(item: index, section: 0), | ||
| for: .delete, | ||
| newIndexPath: nil | ||
| ) | ||
| } | ||
|
|
||
| // Remove the cached items since they're now deleted, technically. It is important for it to be reset before | ||
| // calling `controllerDidChangeContent` so it properly reflects the state | ||
| self.queue.sync { | ||
| self._items = [] | ||
| } | ||
|
|
||
| // Publish the changes | ||
| self.changeAggregator.controllerDidChangeContent(fetchResultsController) | ||
|
|
||
| // Remove delegate so it doesn't get further removal updates | ||
| self.frc.delegate = nil | ||
| } | ||
|
|
||
| // When `DidRemoveAllDataNotification` is received, we need to reset the FRC. At this point, the entities are removed but | ||
| // the FRC doesn't know about it yet. Resetting the FRC removes the content of `FRC.fetchedObjects`. | ||
| let didRemoveAllDataNotificationObserver = notificationCenter.addObserver( | ||
| forName: DatabaseContainer.DidRemoveAllDataNotification, | ||
| object: context, | ||
| queue: .main | ||
| ) { [weak self] _ in | ||
| // Technically, this should rather be `unowned`, however, `deinit` is not always called on the main thread which can | ||
| // cause a race condition when the notification observers are not removed at the right time. | ||
| guard let self = self else { return } | ||
|
|
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| // Reset FRC which causes the current `frc.fetchedObjects` to be reloaded | ||
| do { | ||
| self.isInitialized = false | ||
| try self.startObserving() | ||
| } catch { | ||
| log.error("Error when starting observing: \(error)") | ||
| } | ||
| } | ||
|
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| releaseNotificationObservers = { [weak notificationCenter] in | ||
| notificationCenter?.removeObserver(willRemoveAllDataNotificationObserver) | ||
| notificationCenter?.removeObserver(didRemoveAllDataNotificationObserver) | ||
| } | ||
| } | ||
| } |
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