improved caching in utility methods

CoreStoreDemo/CoreStoreDemo/Info.plist

@@ -51,6 +51,6 @@
 	<key>UIViewControllerBasedStatusBarAppearance</key>
 	<false/>
 	<key>UIUserInterfaceStyle</key>
-	<string>light</string>
+	<string>Light</string>
 </dict>
 </plist>

CoreStoreDemo/CoreStoreDemo/SwiftUI Demo/SwiftUIView.swift

@@ -39,7 +39,7 @@ struct SwiftUIView: View {
     var body: some View {
         NavigationView {
             List {
-                ForEach(palettes.sections, id: \.self) { (sectionID) in
+                ForEach(palettes.sectionIdentifiers, id: \.self) { (sectionID) in
                     Section(header: Text(sectionID)) {
                         ForEach(self.palettes[section: sectionID], id: \.self) { palette in
                             NavigationLink(
@@ -118,7 +118,6 @@ struct SwiftUIView: View {
                 self.needsShowAlert = true
             }
         }
-        .colorScheme(.dark)
     }
 
     @State

Sources/DiffableDataSourceSnapshotProtocol.swift

@@ -31,4 +31,32 @@ import CoreData
 
 internal protocol DiffableDataSourceSnapshotProtocol {
 
+    init()
+
+    var numberOfItems: Int { get }
+    var numberOfSections: Int { get }
+    var sectionIdentifiers: [String] { get }
+    var itemIdentifiers: [NSManagedObjectID] { get }
+
+    func numberOfItems(inSection identifier: String) -> Int
+    func itemIdentifiers(inSection identifier: String) -> [NSManagedObjectID]
+    func sectionIdentifier(containingItem identifier: NSManagedObjectID) -> String?
+    func indexOfItem(_ identifier: NSManagedObjectID) -> Int?
+    func indexOfSection(_ identifier: String) -> Int?
+
+    mutating func appendItems(_ identifiers: [NSManagedObjectID], toSection sectionIdentifier: String?)
+    mutating func insertItems(_ identifiers: [NSManagedObjectID], beforeItem beforeIdentifier: NSManagedObjectID)
+    mutating func insertItems(_ identifiers: [NSManagedObjectID], afterItem afterIdentifier: NSManagedObjectID)
+    mutating func deleteItems(_ identifiers: [NSManagedObjectID])
+    mutating func deleteAllItems()
+    mutating func moveItem(_ identifier: NSManagedObjectID, beforeItem toIdentifier: NSManagedObjectID)
+    mutating func moveItem(_ identifier: NSManagedObjectID, afterItem toIdentifier: NSManagedObjectID)
+    mutating func reloadItems(_ identifiers: [NSManagedObjectID])
+    mutating func appendSections(_ identifiers: [String])
+    mutating func insertSections(_ identifiers: [String], beforeSection toIdentifier: String)
+    mutating func insertSections(_ identifiers: [String], afterSection toIdentifier: String)
+    mutating func deleteSections(_ identifiers: [String])
+    mutating func moveSection(_ identifier: String, beforeSection toIdentifier: String)
+    mutating func moveSection(_ identifier: String, afterSection toIdentifier: String)
+    mutating func reloadSections(_ identifiers: [String])
 }

Sources/Internals.DiffableDataSourceSnapshot.swift

@@ -40,24 +40,26 @@ import AppKit
 
 extension Internals {
 
-
     // MARK: - DiffableDataSourceSnapshot
 
     // Implementation based on https://github.com/ra1028/DiffableDataSources
-    internal struct DiffableDataSourceSnapshot {
+    internal struct DiffableDataSourceSnapshot: DiffableDataSourceSnapshotProtocol {
 
         // MARK: Internal
 
-        init() {
-
-            self.structure = .init()
-        }
-
         init(sections: [NSFetchedResultsSectionInfo]) {
 
             self.structure = .init(sections: sections)
         }
 
+
+        // MARK: DiffableDataSourceSnapshotProtocol
+
+        init() {
+
+            self.structure = .init()
+        }
+
         var numberOfItems: Int {
 
             return self.structure.allItemIDs.count
@@ -68,37 +70,37 @@ extension Internals {
             return self.structure.allSectionIDs.count
         }
 
-        var allSectionIDs: [String] {
+        var sectionIdentifiers: [String] {
 
             return self.structure.allSectionIDs
         }
 
-        var allItemIDs: [NSManagedObjectID] {
+        var itemIdentifiers: [NSManagedObjectID] {
 
             return self.structure.allItemIDs
         }
 
         func numberOfItems(inSection identifier: String) -> Int {
 
-            return self.itemIDs(inSection: identifier).count
+            return self.itemIdentifiers(inSection: identifier).count
         }
 
-        func itemIDs(inSection identifier: String) -> [NSManagedObjectID] {
+        func itemIdentifiers(inSection identifier: String) -> [NSManagedObjectID] {
 
             return self.structure.items(in: identifier)
         }
 
-        func sectionIDs(containingItem identifier: NSManagedObjectID) -> String? {
+        func sectionIdentifier(containingItem identifier: NSManagedObjectID) -> String? {
 
             return self.structure.section(containing: identifier)
         }
 
-        func indexOfItemID(_ identifier: NSManagedObjectID) -> Int? {
+        func indexOfItem(_ identifier: NSManagedObjectID) -> Int? {
 
             return self.structure.allItemIDs.firstIndex(of: identifier)
         }
 
-        func indexOfSectionID(_ identifier: String) -> Int? {
+        func indexOfSection(_ identifier: String) -> Int? {
 
             return self.structure.allSectionIDs.firstIndex(of: identifier)
         }
@@ -138,9 +140,9 @@ extension Internals {
             self.structure.move(itemID: identifier, after: toIdentifier)
         }
 
-        mutating func reloadItems<S: Sequence>(_ identifiers: S, nextStateTag: UUID) where S.Element == NSManagedObjectID {
+        mutating func reloadItems(_ identifiers: [NSManagedObjectID]) {
 
-            self.structure.update(itemIDs: identifiers, nextStateTag: nextStateTag)
+            self.structure.update(itemIDs: identifiers)
         }
 
         mutating func appendSections(_ identifiers: [String]) {
@@ -173,9 +175,9 @@ extension Internals {
             self.structure.move(sectionID: identifier, after: toIdentifier)
         }
 
-        mutating func reloadSections<S: Sequence>(_ identifiers: S, nextStateTag: UUID) where S.Element == String {
+        mutating func reloadSections(_ identifiers: [String]) {
 
-            self.structure.update(sectionIDs: identifiers, nextStateTag: nextStateTag)
+            self.structure.update(sectionIDs: identifiers)
         }
 
 
@@ -388,7 +390,7 @@ extension Internals {
                     .insert(removed, at: itemIndex)
             }
 
-            mutating func update<S: Sequence>(itemIDs: S, nextStateTag: UUID) where S.Element == NSManagedObjectID {
+            mutating func update<S: Sequence>(itemIDs: S) where S.Element == NSManagedObjectID {
 
                 let itemPositionMap = self.itemPositionMap()
                 for itemID in itemIDs {
@@ -464,7 +466,7 @@ extension Internals {
                 self.sections.insert(removed, at: sectionIndex)
             }
 
-            mutating func update<S: Sequence>(sectionIDs: S, nextStateTag: UUID) where S.Element == String {
+            mutating func update<S: Sequence>(sectionIDs: S) where S.Element == String {
 
                 for sectionID in sectionIDs {
 
@@ -590,4 +592,76 @@ extension Internals {
 }
 
 
+// MARK: - NSDiffableDataSourceSnapshot: DiffableDataSourceSnapshotProtocol
+
+@available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 15.0, *)
+extension NSDiffableDataSourceSnapshot: DiffableDataSourceSnapshotProtocol where SectionIdentifierType == NSString, ItemIdentifierType == NSManagedObjectID {
+
+    internal var sectionIdentifiers: [String] {
+
+        return self.sectionIdentifiers as [NSString] as [String]
+    }
+
+    internal func numberOfItems(inSection identifier: String) -> Int {
+
+        return self.numberOfItems(inSection: identifier as NSString)
+    }
+
+    internal func itemIdentifiers(inSection identifier: String) -> [NSManagedObjectID] {
+
+        return self.itemIdentifiers(inSection: identifier as NSString)
+    }
+
+    internal func sectionIdentifier(containingItem identifier: NSManagedObjectID) -> String? {
+
+        return self.sectionIdentifier(containingItem: identifier) as NSString? as String?
+    }
+
+    internal func indexOfSection(_ identifier: String) -> Int? {
+
+        return self.indexOfSection(identifier as NSString)
+    }
+
+    internal mutating func appendItems(_ identifiers: [NSManagedObjectID], toSection sectionIdentifier: String?) {
+
+        self.appendItems(identifiers, toSection: sectionIdentifier as NSString?)
+    }
+
+    internal mutating func appendSections(_ identifiers: [String]) {
+
+        self.appendSections(identifiers as [NSString])
+    }
+
+    internal mutating func insertSections(_ identifiers: [String], beforeSection toIdentifier: String) {
+
+        self.insertSections(identifiers as [NSString], beforeSection: toIdentifier as NSString)
+    }
+
+    internal mutating func insertSections(_ identifiers: [String], afterSection toIdentifier: String) {
+
+        return self.insertSections(identifiers as [NSString], afterSection: toIdentifier as NSString)
+    }
+
+    internal mutating func deleteSections(_ identifiers: [String]) {
+
+        self.deleteSections(identifiers as [NSString])
+    }
+
+    internal mutating func moveSection(_ identifier: String, beforeSection toIdentifier: String) {
+
+        self.moveSection(identifier as NSString, beforeSection: toIdentifier as NSString)
+    }
+
+    internal mutating func moveSection(_ identifier: String, afterSection toIdentifier: String) {
+
+        self.moveSection(identifier as NSString, afterSection: toIdentifier as NSString)
+    }
+
+    internal mutating func reloadSections(_ identifiers: [String]) {
+
+        self.reloadSections(identifiers as [NSString])
+    }
+}
+
+
 #endif

Sources/Internals.FetchedDiffableDataSourceSnapshotDelegate.swift

@@ -41,7 +41,7 @@ import AppKit
 
 internal protocol FetchedDiffableDataSourceSnapshotHandler: AnyObject {
 
-    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangContentWith snapshot: Internals.DiffableDataSourceSnapshot)
+    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: DiffableDataSourceSnapshotProtocol)
 }
 
 
@@ -75,14 +75,14 @@ extension Internals {
 
         internal func initialFetch() {
 
-//            #if canImport(UIKit) || canImport(AppKit)
+            #if canImport(UIKit) || canImport(AppKit)
-//
+
-//            if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
+            if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
-//
+
-//                return
+                return
-//            }
+            }
-//
+
-//            #endif
+            #endif
 
             guard let fetchedResultsController = self.fetchedResultsController else {
 
@@ -94,26 +94,26 @@ extension Internals {
 
         // MARK: NSFetchedResultsControllerDelegate
 
-//        #if canImport(UIKit) || canImport(AppKit)
+        #if canImport(UIKit) || canImport(AppKit)
-//
+
-//        @available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *)
+        @available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *)
-//        @objc
+        @objc
-//        dynamic func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: NSDiffableDataSourceSnapshotReference) {
+        dynamic func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: NSDiffableDataSourceSnapshotReference) {
-//
+
-//            self.handler?.controller(
+            self.handler?.controller(
-//                controller,
+                controller,
-//                didChangContentWith: snapshot as NSDiffableDataSourceSnapshot<NSString, NSManagedObjectID>
+                didChangeContentWith: snapshot as NSDiffableDataSourceSnapshot<NSString, NSManagedObjectID>
-//            )
+            )
-//        }
+        }
-//
+
-//        #endif
+        #endif
         
         @objc
         dynamic func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
 
             self.handler?.controller(
                 controller,
-                didChangContentWith: Internals.DiffableDataSourceSnapshot(
+                didChangeContentWith: Internals.DiffableDataSourceSnapshot(
                     sections: controller.sections ?? []
                 )
             )

Sources/Internals.SharedNotificationObserver.swift

@@ -25,32 +25,83 @@
 
 import Foundation
 
-
 // MARK: - Internal
 
 extension Internals {
 
     // MARK: - SharedNotificationObserver
 
-    internal final class SharedNotificationObserver {
+    internal final class SharedNotificationObserver<T> {
 
         // MARK: Internal
 
-        let observer: NSObjectProtocol
+        internal init(notificationName: Notification.Name, object: Any?, queue: OperationQueue? = nil, sharedValue: @escaping (_ note: Notification) -> T) {
-
-        init(notificationName: Notification.Name, object: Any?, queue: OperationQueue? = nil, closure: @escaping (_ note: Notification) -> Void) {
 
             self.observer = NotificationCenter.default.addObserver(
                 forName: notificationName,
                 object: object,
                 queue: queue,
-                using: closure
+                using: { [weak self] (notification) in
+
+                    guard let self = self else {
+
+                        return
+                    }
+                    let value = sharedValue(notification)
+                    self.notifyObservers(value)
+                }
             )
         }
 
         deinit {
 
-            NotificationCenter.default.removeObserver(self.observer)
+            self.observer.map(NotificationCenter.default.removeObserver(_:))
+        }
+
+        internal func addObserver<U: AnyObject>(_ observer: U, closure: @escaping (T) -> Void) {
+
+            self.observers.setObject(Closure(closure), forKey: observer)
+        }
+
+
+        // MARK: Private
+
+        private var observer: NSObjectProtocol!
+        private let observers: NSMapTable<AnyObject, Closure> = .weakToStrongObjects()
+
+        private func notifyObservers(_ sharedValue: T) {
+
+            guard let enumerator = self.observers.objectEnumerator() else {
+
+                return
+            }
+            for closure in enumerator {
+
+                (closure as! Closure).invoke(with: sharedValue)
+            }
+        }
+
+
+        // MARK: - Closure
+
+        fileprivate final class Closure {
+
+            // MARK: FilePrivate
+
+            fileprivate init(_ closure: @escaping (T) -> Void) {
+
+                self.closure = closure
+            }
+
+            fileprivate func invoke(with argument: T) {
+
+                self.closure(argument)
+            }
+
+
+            // MARK: Private
+
+            private let closure: (T) -> Void
         }
     }
 }

Sources/ListSnapshot.swift

@@ -46,7 +46,7 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
     public subscript<S: Sequence>(indices indices: S) -> [LiveObject<O>] where S.Element == Index {
 
         let context = self.context!
-        let itemIDs = self.diffableSnapshot.allItemIDs
+        let itemIDs = self.diffableSnapshot.itemIdentifiers
         return indices.map { position in
 
             let itemID = itemIDs[position]
@@ -57,7 +57,7 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
     public subscript(section sectionID: SectionID) -> [LiveObject<O>] {
 
         let context = self.context!
-        let itemIDs = self.diffableSnapshot.itemIDs(inSection: sectionID)
+        let itemIDs = self.diffableSnapshot.itemIdentifiers(inSection: sectionID)
         return itemIDs.map {
 
             return LiveObject<O>(id: $0, context: context)
@@ -67,7 +67,7 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
     public subscript<S: Sequence>(section sectionID: SectionID, itemIndices itemIndices: S) -> [LiveObject<O>] where S.Element == Int {
 
         let context = self.context!
-        let itemIDs = self.diffableSnapshot.itemIDs(inSection: sectionID)
+        let itemIDs = self.diffableSnapshot.itemIdentifiers(inSection: sectionID)
         return itemIndices.map { position in
 
             let itemID = itemIDs[position]
@@ -85,14 +85,14 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
         return self.diffableSnapshot.numberOfSections
     }
 
-    public var sectionIDs: [SectionID] {
+    public var sectionIdentifiers: [SectionID] {
 
-        return self.diffableSnapshot.allSectionIDs
+        return self.diffableSnapshot.sectionIdentifiers
     }
 
     public var itemIdentifiers: [ItemID] {
 
-        return self.diffableSnapshot.allItemIDs
+        return self.diffableSnapshot.itemIdentifiers
     }
 
     public func numberOfItems(inSection identifier: SectionID) -> Int {
@@ -102,28 +102,28 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
 
     public func itemIdentifiers(inSection identifier: SectionID) -> [ItemID] {
 
-        return self.diffableSnapshot.itemIDs(inSection: identifier)
+        return self.diffableSnapshot.itemIdentifiers(inSection: identifier)
     }
 
     public func itemIdentifiers(inSection identifier: SectionID, atIndices indices: IndexSet) -> [ItemID] {
 
-        let itemIDs = self.diffableSnapshot.itemIDs(inSection: identifier)
+        let itemIDs = self.diffableSnapshot.itemIdentifiers(inSection: identifier)
         return indices.map({ itemIDs[$0] })
     }
 
     public func sectionIdentifier(containingItem identifier: ItemID) -> SectionID? {
 
-        return self.diffableSnapshot.sectionIDs(containingItem: identifier)
+        return self.diffableSnapshot.sectionIdentifier(containingItem: identifier)
     }
 
     public func indexOfItem(_ identifier: ItemID) -> Index? {
 
-        return self.diffableSnapshot.indexOfItemID(identifier)
+        return self.diffableSnapshot.indexOfItem(identifier)
     }
 
     public func indexOfSection(_ identifier: SectionID) -> Int? {
 
-        return self.diffableSnapshot.indexOfSectionID(identifier)
+        return self.diffableSnapshot.indexOfSection(identifier)
     }
 
     public mutating func appendItems(_ identifiers: [ItemID], toSection sectionIdentifier: SectionID? = nil) {
@@ -163,7 +163,7 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
 
     public mutating func reloadItems(_ identifiers: [ItemID]) {
 
-        self.diffableSnapshot.reloadItems(identifiers, nextStateTag: .init())
+        self.diffableSnapshot.reloadItems(identifiers)
     }
 
     public mutating func appendSections(_ identifiers: [SectionID]) {
@@ -198,7 +198,7 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
 
     public mutating func reloadSections(_ identifiers: [SectionID]) {
 
-        self.diffableSnapshot.reloadSections(identifiers, nextStateTag: .init())
+        self.diffableSnapshot.reloadSections(identifiers)
     }
     
     
@@ -211,18 +211,18 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
     
     public var startIndex: Index {
         
-        return self.diffableSnapshot.allItemIDs.startIndex
+        return self.diffableSnapshot.itemIdentifiers.startIndex
     }
     
     public var endIndex: Index {
         
-        return self.diffableSnapshot.allItemIDs.endIndex
+        return self.diffableSnapshot.itemIdentifiers.endIndex
     }
     
     public subscript(position: Index) -> Element {
         
         let context = self.context!
-        let itemID = self.diffableSnapshot.allItemIDs[position]
+        let itemID = self.diffableSnapshot.itemIdentifiers[position]
         return LiveObject<O>(id: itemID, context: context)
     }
     
@@ -254,11 +254,11 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
     
     internal init() {
 
-        self.diffableSnapshot = .init()
+        self.diffableSnapshot = Internals.DiffableDataSourceSnapshot()
         self.context = nil
     }
     
-    internal init(diffableSnapshot: Internals.DiffableDataSourceSnapshot, context: NSManagedObjectContext) {
+    internal init(diffableSnapshot: DiffableDataSourceSnapshotProtocol, context: NSManagedObjectContext) {
 
         self.diffableSnapshot = diffableSnapshot
         self.context = context
@@ -270,5 +270,5 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
     private let id: UUID = .init()
     private let context: NSManagedObjectContext?
 
-    private var diffableSnapshot: Internals.DiffableDataSourceSnapshot
+    private var diffableSnapshot: DiffableDataSourceSnapshotProtocol
 }

Sources/LiveList.swift

@@ -63,9 +63,9 @@ public final class LiveList<O: DynamicObject>: Hashable {
         return self.snapshot.numberOfSections
     }
 
-    public var sections: [SectionID] {
+    public var sectionIdentifiers: [SectionID] {
 
-        return self.snapshot.sectionIDs
+        return self.snapshot.sectionIdentifiers
     }
 
     public subscript(section sectionID: SectionID) -> [LiveObject<O>] {
@@ -302,7 +302,7 @@ extension LiveList: FetchedDiffableDataSourceSnapshotHandler {
 
     // MARK: FetchedDiffableDataSourceSnapshotHandler
 
-    internal func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangContentWith snapshot: Internals.DiffableDataSourceSnapshot) {
+    internal func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: DiffableDataSourceSnapshotProtocol) {
 
         self.snapshot = .init(
             diffableSnapshot: snapshot,

Sources/LiveObject.swift

@@ -114,36 +114,23 @@ public final class LiveObject<O: DynamicObject>: Identifiable, Hashable {
 
             self.rawObjectWillChange = nil
         }
-        self.observer = NotificationCenter.default.addObserver(
-            forName: .NSManagedObjectContextObjectsDidChange,
-            object: context,
-            queue: .main,
-            using: { [weak self] (notification) in
-
-                guard let self = self, let userInfo = notification.userInfo else {
-
-                    return
-                }
-                let updatedObjects = (userInfo[NSUpdatedObjectsKey] as! NSSet? ?? [])
-                let mergedObjects = (userInfo[NSRefreshedObjectsKey] as! NSSet? ?? [])
-                guard mergedObjects.contains(where: { ($0 as! NSManagedObject).objectID == id })
-                    || updatedObjects.contains(where: { ($0 as! NSManagedObject).objectID == id }) else {
-
-                        return
-                }
-                self.$lazySnapshot.reset({ initializer(id, context) })
-                self.willChange()
-            }
-        )
-
         self.$lazySnapshot.initialize({ initializer(id, context) })
+        
+        context.objectsDidChangeObserver(for: self).addObserver(self) { [weak self] (objectIDs) in
+
+            guard let self = self else {
+
+                return
+            }
+            self.$lazySnapshot.reset({ initializer(id, context) })
+            self.willChange()
+        }
     }
 
 
     // MARK: Private
     
     private let context: NSManagedObjectContext
-    private var observer: NSObjectProtocol?
 
     @Internals.LazyNonmutating(uninitialized: ())
     private var lazySnapshot: ObjectSnapshot<O>

Sources/NSManagedObjectContext+CoreStore.swift

@@ -89,7 +89,10 @@ extension NSManagedObjectContext {
     @nonobjc
     internal func liveObject<D: DynamicObject>(id: NSManagedObjectID) -> LiveObject<D> {
 
-        let cache = self.liveObjectsCache(D.self)
+        let cache: NSMapTable<NSManagedObjectID, LiveObject<D>> = self.userInfo(for: .liveObjectsCache(D.self)) {
+
+            return .strongToWeakObjects()
+        }
         return Internals.with {
 
             if let liveObject = cache.object(forKey: id) {
@@ -103,27 +106,38 @@ extension NSManagedObjectContext {
     }
 
     @nonobjc
-    private func liveObjectsCache<D: DynamicObject>(_ objectType: D.Type) -> NSMapTable<NSManagedObjectID, LiveObject<D>> {
+    internal func objectsDidChangeObserver<U: AnyObject>(for observer: U) -> Internals.SharedNotificationObserver<Set<NSManagedObjectID>> {
 
-        let key = Internals.typeName(objectType)
+        return self.userInfo(for: .objectsChangeObserver(U.self)) { [unowned self] in
-        if let cache = self.userInfo[key] {
 
-            return cache as! NSMapTable<NSManagedObjectID, LiveObject<D>>
+            return .init(
+                notificationName: .NSManagedObjectContextObjectsDidChange,
+                object: self,
+                queue: .main,
+                sharedValue: { (notification) -> Set<NSManagedObjectID> in
+
+                    guard let userInfo = notification.userInfo else {
+
+                        return []
+                    }
+                    var updatedObjectIDs: Set<NSManagedObjectID> = []
+                    if let updatedObjects = userInfo[NSUpdatedObjectsKey] as? Set<NSManagedObjectID> {
+
+                        updatedObjectIDs.formUnion(updatedObjects)
+                    }
+                    if let mergedObjects = userInfo[NSRefreshedObjectsKey] as? Set<NSManagedObjectID> {
+
+                        updatedObjectIDs.formUnion(mergedObjects)
+                    }
+                    return updatedObjectIDs
+                }
+            )
         }
-        let cache = NSMapTable<NSManagedObjectID, LiveObject<D>>.strongToWeakObjects()
-        self.userInfo[key] = cache
-        return cache
     }
     
     
     // MARK: Private
     
-    private struct PropertyKeys {
-        
-        static var observerForWillSaveNotification: Void?
-        static var shouldCascadeSavesToParent: Void?
-    }
-    
     @nonobjc
     private var observerForWillSaveNotification: Internals.NotificationObserver? {
         
@@ -143,5 +157,47 @@ extension NSManagedObjectContext {
             )
         }
     }
+
+    private func userInfo<T>(for key: UserInfoKeys, initialize: @escaping () -> T) -> T {
+
+        let keyString = key.keyString
+        if let value = self.userInfo[keyString] {
+
+            return value as! T
+        }
+        let value = initialize()
+        self.userInfo[keyString] = value
+        return value
+    }
+
+
+    // MARK: - PropertyKeys
+
+    private struct PropertyKeys {
+
+        static var observerForWillSaveNotification: Void?
+        static var shouldCascadeSavesToParent: Void?
+    }
+
+
+    // MARK: - UserInfoKeys
+
+    private enum UserInfoKeys {
+
+        case liveObjectsCache(DynamicObject.Type)
+        case objectsChangeObserver(AnyObject.Type)
+
+        var keyString: String {
+
+            switch self {
+
+            case .liveObjectsCache(let objectType):
+                return "CoreStore.liveObjectsCache(\(Internals.typeName(objectType)))"
+
+            case .objectsChangeObserver:
+                return "CoreStore.objectsChangeObserver"
+            }
+        }
+    }
 }