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 				B5D339F41E94AF5800C880DE /* CoreStoreStrings.swift in Sources */,
 				B5220E241D13085E009BC71E /* NSFetchedResultsController+Convenience.swift in Sources */,
 				B559CD471CAA8B6300E4D58B /* CSSetupResult.swift in Sources */,
+				B50E17642351FA66004F033C /* Internals.Closure.swift in Sources */,
 				B5ECDBF01CA6BF2000C7F112 /* CSFrom.swift in Sources */,
 				B549F6761E56A92800FBAB2D /* CoreDataNativeType.swift in Sources */,
 				B509C7F71E54511B0061C547 /* ImportableAttributeType.swift in Sources */,
@@ -2615,11 +2657,13 @@
 				B5220E1A1D130791009BC71E /* Internals.CoreStoreFetchedResultsController.swift in Sources */,
 				B5215CAC1FA4810300139E3A /* QueryChainBuilder.swift in Sources */,
 				B53FBA0F1CAB5E6500F0D40A /* CSCoreStore+Migrating.swift in Sources */,
+				B50E175A23517DE4004F033C /* Differentiable.swift in Sources */,
 				B52F744D1E9B8740005F3DAC /* CoreStoreSchema.swift in Sources */,
 				B52DD19A1BE1F92800949AFE /* CoreStore+Logging.swift in Sources */,
 				B52DD1A71BE1F93200949AFE /* BaseDataTransaction+Querying.swift in Sources */,
 				B546F96C1C9AF26D00D5AC55 /* CSInMemoryStore.swift in Sources */,
 				B56923EB1EB827F5007C4DC9 /* InferredSchemaMappingProvider.swift in Sources */,
+				B50E175023517C03004F033C /* Internals.DiffableDataUIDispatcher.StagedChangeset.swift in Sources */,
 				B53B27621EE3B92E00E9B352 /* CoreStoreManagedObject.swift in Sources */,
 				B5215CA71FA47DFD00139E3A /* FetchChainBuilder.swift in Sources */,
 				B5D33A041E96012400C880DE /* Relationship.swift in Sources */,
@@ -2655,6 +2699,7 @@
 				B52F74401E9B8724005F3DAC /* DynamicSchema.swift in Sources */,
 				18166886232B9ED20097C275 /* KeyPath+KeyPaths.swift in Sources */,
 				B5E8A72321C1015300EF006A /* CoreStoreObject+Observing.swift in Sources */,
+				B50E175F2351848E004F033C /* Internals.DiffableDataUIDispatcher.DiffResult.swift in Sources */,
 				B5474D182227C08700B21FEC /* Internals.CoreStoreFetchRequest.swift in Sources */,
 				B501322E2346A9B100FC238B /* LiveList.swift in Sources */,
 				B56924021EB82976007C4DC9 /* CSUnsafeDataModelSchema.swift in Sources */,
@@ -2726,7 +2771,7 @@
 				B56321AD1BD6521C006C9394 /* Internals.MigrationManager.swift in Sources */,
 				B563219D1BD65216006C9394 /* DataStack+Observing.swift in Sources */,
 				B56321961BD65216006C9394 /* From.swift in Sources */,
-				B5BF7FBE234C99190070E741 /* Internals.FallbackDiffableDataUIDispatcher.swift in Sources */,
+				B5BF7FBE234C99190070E741 /* Internals.DiffableDataUIDispatcher.swift in Sources */,
 				B5D339DA1E9489AB00C880DE /* CoreStoreObject.swift in Sources */,
 				B5ECDC021CA80CBA00C7F112 /* CSWhere.swift in Sources */,
 				B56923FC1EB82956007C4DC9 /* CSXcodeDataModelSchema.swift in Sources */,
@@ -2745,6 +2790,7 @@
 				B5A992211EA898720091A2E3 /* UserInfo.swift in Sources */,
 				B563218C1BD65216006C9394 /* DataStack+Transaction.swift in Sources */,
 				B5D339E41E948C3600C880DE /* Value.swift in Sources */,
+				B50E175423517C6B004F033C /* Internals.DiffableDataUIDispatcher.Changeset.swift in Sources */,
 				B53FBA0E1CAB5E6500F0D40A /* CSCoreStore+Migrating.swift in Sources */,
 				B563219E1BD65216006C9394 /* CoreStore+Observing.swift in Sources */,
 				B5D7A5B91CA3BF8F005C752B /* CSInto.swift in Sources */,
@@ -2762,6 +2808,7 @@
 				B5D339F31E94AF5800C880DE /* CoreStoreStrings.swift in Sources */,
 				B5E1B5A01CAA2568007FD580 /* CSDataStack+Observing.swift in Sources */,
 				B5ECDC261CA81A3900C7F112 /* CSCoreStore+Querying.swift in Sources */,
+				B50E17632351FA66004F033C /* Internals.Closure.swift in Sources */,
 				B563217F1BD65216006C9394 /* CoreStore.swift in Sources */,
 				B549F6751E56A92800FBAB2D /* CoreDataNativeType.swift in Sources */,
 				B509C7F61E54511B0061C547 /* ImportableAttributeType.swift in Sources */,
@@ -2834,11 +2881,13 @@
 				B56321A51BD65216006C9394 /* MigrationChain.swift in Sources */,
 				B5E222261CA4E12600BA2E95 /* CSSynchronousDataTransaction.swift in Sources */,
 				B56321A21BD65216006C9394 /* ListObserver.swift in Sources */,
+				B50E175923517DE4004F033C /* Differentiable.swift in Sources */,
 				B5215CAB1FA4810300139E3A /* QueryChainBuilder.swift in Sources */,
 				B563218A1BD65216006C9394 /* SynchronousDataTransaction.swift in Sources */,
 				B52F744C1E9B8740005F3DAC /* CoreStoreSchema.swift in Sources */,
 				B5AEFAB71C9962AE00AD137F /* CoreStoreBridge.swift in Sources */,
 				B5E2222D1CA51B6E00BA2E95 /* CSUnsafeDataTransaction.swift in Sources */,
+				B50E174F23517C03004F033C /* Internals.DiffableDataUIDispatcher.StagedChangeset.swift in Sources */,
 				B563219F1BD65216006C9394 /* ObjectMonitor.swift in Sources */,
 				B56321B61BD6521C006C9394 /* Internals.WeakObject.swift in Sources */,
 				B56923EA1EB827F5007C4DC9 /* InferredSchemaMappingProvider.swift in Sources */,
@@ -2874,6 +2923,7 @@
 				B52F743F1E9B8724005F3DAC /* DynamicSchema.swift in Sources */,
 				18166885232B9ED10097C275 /* KeyPath+KeyPaths.swift in Sources */,
 				B5E8A72221C1015300EF006A /* CoreStoreObject+Observing.swift in Sources */,
+				B50E175E2351848E004F033C /* Internals.DiffableDataUIDispatcher.DiffResult.swift in Sources */,
 				B5474D172227C08700B21FEC /* Internals.CoreStoreFetchRequest.swift in Sources */,
 				B501322D2346A9B000FC238B /* LiveList.swift in Sources */,
 				B56924011EB82976007C4DC9 /* CSUnsafeDataModelSchema.swift in Sources */,

CoreStoreDemo/CoreStoreDemo/Base.lproj/Main.storyboard

@@ -510,18 +510,18 @@
                         <viewControllerLayoutGuide type="bottom" id="aI4-O3-OCi"/>
                     </layoutGuides>
                     <view key="view" contentMode="scaleToFill" id="w8K-eN-RvU">
-                        <rect key="frame" x="0.0" y="0.0" width="375" height="309"/>
+                        <rect key="frame" x="0.0" y="0.0" width="375" height="311.5"/>
                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                         <subviews>
                             <view contentMode="scaleToFill" verticalCompressionResistancePriority="250" translatesAutoresizingMaskIntoConstraints="NO" id="NhC-oM-bkd">
-                                <rect key="frame" x="16" y="69.5" width="343" height="77.5"/>
+                                <rect key="frame" x="16" y="69.5" width="343" height="80"/>
                                 <color key="backgroundColor" red="1" green="1" blue="1" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                 <constraints>
                                     <constraint firstAttribute="height" relation="greaterThanOrEqual" id="TIX-qi-B34"/>
                                 </constraints>
                             </view>
                             <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" verticalCompressionResistancePriority="250" text="Label" textAlignment="center" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" minimumScaleFactor="0.5" adjustsLetterSpacingToFitWidth="YES" translatesAutoresizingMaskIntoConstraints="NO" id="Vfe-Yq-3Xa">
-                                <rect key="frame" x="16" y="157" width="343" height="18"/>
+                                <rect key="frame" x="16" y="159.5" width="343" height="18"/>
                                 <constraints>
                                     <constraint firstAttribute="height" relation="greaterThanOrEqual" id="4h9-ha-EzR"/>
                                 </constraints>
@@ -530,37 +530,37 @@
                                 <nil key="highlightedColor"/>
                             </label>
                             <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Hue" textAlignment="right" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="sgg-Md-Nf3">
-                                <rect key="frame" x="16" y="195" width="74" height="18"/>
+                                <rect key="frame" x="16" y="197.5" width="74" height="18"/>
                                 <fontDescription key="fontDescription" type="system" pointSize="15"/>
                                 <color key="textColor" red="0.0" green="0.0" blue="0.0" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                 <nil key="highlightedColor"/>
                             </label>
                             <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Saturation" textAlignment="right" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="rry-vh-bRK">
-                                <rect key="frame" x="16" y="233" width="74" height="18"/>
+                                <rect key="frame" x="16" y="235.5" width="74" height="18"/>
                                 <fontDescription key="fontDescription" type="system" pointSize="15"/>
                                 <color key="textColor" red="0.0" green="0.0" blue="0.0" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                 <nil key="highlightedColor"/>
                             </label>
                             <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Brightness" textAlignment="right" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="vTa-ly-eyO">
-                                <rect key="frame" x="16" y="271" width="74" height="18"/>
+                                <rect key="frame" x="16" y="273.5" width="74" height="18"/>
                                 <fontDescription key="fontDescription" type="system" pointSize="15"/>
                                 <color key="textColor" red="0.0" green="0.0" blue="0.0" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                 <nil key="highlightedColor"/>
                             </label>
                             <slider opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" minValue="0.0" maxValue="359" translatesAutoresizingMaskIntoConstraints="NO" id="YQ6-fq-3Wb">
-                                <rect key="frame" x="98" y="189" width="263" height="31"/>
+                                <rect key="frame" x="98" y="191.5" width="263" height="31"/>
                                 <connections>
                                     <action selector="hueSliderValueDidChange:" destination="dX3-kR-CYC" eventType="valueChanged" id="9Hy-3h-llE"/>
                                 </connections>
                             </slider>
                             <slider opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" value="1" minValue="0.0" maxValue="1" translatesAutoresizingMaskIntoConstraints="NO" id="xXz-78-tAd">
-                                <rect key="frame" x="98" y="227" width="263" height="31"/>
+                                <rect key="frame" x="98" y="229.5" width="263" height="31"/>
                                 <connections>
                                     <action selector="saturationSliderValueDidChange:" destination="dX3-kR-CYC" eventType="valueChanged" id="qtU-ua-ZTc"/>
                                 </connections>
                             </slider>
                             <slider opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" value="0.5" minValue="0.0" maxValue="1" translatesAutoresizingMaskIntoConstraints="NO" id="hpy-2d-eOP">
-                                <rect key="frame" x="98" y="265" width="263" height="31"/>
+                                <rect key="frame" x="98" y="267.5" width="263" height="31"/>
                                 <connections>
                                     <action selector="brightnessSliderValueDidChange:" destination="dX3-kR-CYC" eventType="valueChanged" id="F09-EP-2iD"/>
                                 </connections>
@@ -637,34 +637,52 @@
                         <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                         <subviews>
-                            <containerView opaque="NO" contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="L5f-tW-lXf">
+                            <stackView opaque="NO" contentMode="scaleToFill" axis="vertical" distribution="fillEqually" translatesAutoresizingMaskIntoConstraints="NO" id="cce-yT-4dn">
-                                <rect key="frame" x="0.0" y="44" width="375" height="311.5"/>
+                                <rect key="frame" x="0.0" y="44" width="375" height="623"/>
-                                <connections>
+                                <subviews>
-                                    <segue destination="5Fw-je-9gI" kind="embed" id="YcI-2Z-ijV"/>
+                                    <containerView opaque="NO" contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="L5f-tW-lXf">
-                                </connections>
+                                        <rect key="frame" x="0.0" y="0.0" width="375" height="311.5"/>
-                            </containerView>
+                                        <connections>
-                            <containerView opaque="NO" contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="6So-f3-4Gp">
+                                            <segue destination="5Fw-je-9gI" kind="embed" id="YcI-2Z-ijV"/>
-                                <rect key="frame" x="0.0" y="355.5" width="375" height="311.5"/>
+                                        </connections>
-                                <connections>
+                                    </containerView>
-                                    <segue destination="bLr-DM-i2t" kind="embed" id="OdS-gZ-CUA"/>
+                                    <containerView opaque="NO" contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="6So-f3-4Gp">
-                                </connections>
+                                        <rect key="frame" x="0.0" y="311.5" width="375" height="311.5"/>
-                            </containerView>
+                                        <connections>
+                                            <segue destination="bLr-DM-i2t" kind="embed" id="OdS-gZ-CUA"/>
+                                        </connections>
+                                    </containerView>
+                                </subviews>
+                            </stackView>
                         </subviews>
                         <color key="backgroundColor" red="1" green="1" blue="1" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                         <constraints>
-                            <constraint firstItem="6So-f3-4Gp" firstAttribute="top" secondItem="L5f-tW-lXf" secondAttribute="bottom" id="3m8-tj-Nd4"/>
+                            <constraint firstAttribute="trailing" secondItem="cce-yT-4dn" secondAttribute="trailing" id="DE1-u6-1mr"/>
-                            <constraint firstAttribute="trailing" secondItem="6So-f3-4Gp" secondAttribute="trailing" id="4L8-wZ-F59"/>
+                            <constraint firstItem="LNL-mj-D7l" firstAttribute="top" secondItem="cce-yT-4dn" secondAttribute="bottom" id="WIZ-M3-bdr"/>
-                            <constraint firstItem="L5f-tW-lXf" firstAttribute="height" secondItem="6So-f3-4Gp" secondAttribute="height" id="8XS-L3-hvN"/>
+                            <constraint firstItem="cce-yT-4dn" firstAttribute="leading" secondItem="6x3-vn-Egt" secondAttribute="leading" id="ZiS-j0-ANp"/>
-                            <constraint firstAttribute="bottom" secondItem="6So-f3-4Gp" secondAttribute="bottom" id="8wL-zm-wnt"/>
+                            <constraint firstItem="cce-yT-4dn" firstAttribute="top" secondItem="IML-3o-caw" secondAttribute="bottom" id="zjs-CM-7r5"/>
-                            <constraint firstItem="L5f-tW-lXf" firstAttribute="leading" secondItem="6x3-vn-Egt" secondAttribute="leading" id="CbE-2f-7wk"/>
-                            <constraint firstAttribute="trailing" secondItem="L5f-tW-lXf" secondAttribute="trailing" id="dso-2g-fgA"/>
-                            <constraint firstItem="6So-f3-4Gp" firstAttribute="leading" secondItem="6x3-vn-Egt" secondAttribute="leading" id="eXM-D3-NLv"/>
-                            <constraint firstItem="L5f-tW-lXf" firstAttribute="top" secondItem="IML-3o-caw" secondAttribute="bottom" id="zJ5-sE-iJA"/>
                         </constraints>
                     </view>
                     <extendedEdge key="edgesForExtendedLayout" top="YES"/>
-                    <navigationItem key="navigationItem" title="Colors" id="7Gd-Ad-Bzu"/>
+                    <navigationItem key="navigationItem" title="Colors" id="7Gd-Ad-Bzu">
+                        <rightBarButtonItems>
+                            <barButtonItem title="▼" width="36" id="aPM-OC-EB8">
+                                <connections>
+                                    <action selector="toggleBottomContainerView" destination="YOI-b7-Nxn" id="7fn-z6-pne"/>
+                                </connections>
+                            </barButtonItem>
+                            <barButtonItem title="▲" width="36" id="6q3-Zk-A9p">
+                                <connections>
+                                    <action selector="toggleTopContainerView" destination="YOI-b7-Nxn" id="APN-Kk-C3n"/>
+                                </connections>
+                            </barButtonItem>
+                        </rightBarButtonItems>
+                    </navigationItem>
                     <nil key="simulatedBottomBarMetrics"/>
+                    <connections>
+                        <outlet property="bottomContainerView" destination="6So-f3-4Gp" id="C7O-e2-k0l"/>
+                        <outlet property="topContainerView" destination="L5f-tW-lXf" id="DRV-mm-rBY"/>
+                    </connections>
                 </viewController>
                 <placeholder placeholderIdentifier="IBFirstResponder" id="C9h-Ba-WoL" userLabel="First Responder" sceneMemberID="firstResponder"/>
             </objects>
@@ -700,7 +718,7 @@
             <objects>
                 <tableViewController id="3AE-ED-0oj" customClass="ListObserverDemoViewController" customModule="CoreStoreDemo" customModuleProvider="target" sceneMemberID="viewController">
                     <tableView key="view" clipsSubviews="YES" contentMode="scaleToFill" alwaysBounceVertical="YES" dataMode="prototypes" style="plain" separatorStyle="default" rowHeight="44" sectionHeaderHeight="22" sectionFooterHeight="22" id="DAz-BE-6Ca">
-                        <rect key="frame" x="0.0" y="0.0" width="375" height="309"/>
+                        <rect key="frame" x="0.0" y="0.0" width="375" height="311.5"/>
                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                         <prototypes>
                             <tableViewCell contentMode="scaleToFill" selectionStyle="default" accessoryType="disclosureIndicator" indentationWidth="10" reuseIdentifier="PaletteTableViewCell" id="G3X-70-BCD" customClass="PaletteTableViewCell" customModule="CoreStoreDemo" customModuleProvider="target">
@@ -885,11 +903,11 @@
                         <viewControllerLayoutGuide type="bottom" id="Q1w-Zn-fPm"/>
                     </layoutGuides>
                     <view key="view" contentMode="scaleToFill" id="kof-sr-Xm1">
-                        <rect key="frame" x="0.0" y="0.0" width="375" height="309"/>
+                        <rect key="frame" x="0.0" y="0.0" width="375" height="311.5"/>
                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                         <subviews>
                             <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" verticalCompressionResistancePriority="250" text="SwiftUI is not supported on this device/OS version" textAlignment="center" lineBreakMode="tailTruncation" numberOfLines="0" baselineAdjustment="alignBaselines" minimumScaleFactor="0.5" adjustsLetterSpacingToFitWidth="YES" translatesAutoresizingMaskIntoConstraints="NO" id="M6C-fv-74B">
-                                <rect key="frame" x="16" y="124.5" width="343" height="60"/>
+                                <rect key="frame" x="16" y="126" width="343" height="60"/>
                                 <fontDescription key="fontDescription" name="HelveticaNeue-Bold" family="Helvetica Neue" pointSize="25"/>
                                 <color key="textColor" white="0.66666666666666663" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
                                 <nil key="highlightedColor"/>

CoreStoreDemo/CoreStoreDemo/List and Object Observers Demo/ListObserverDemoViewController.swift

@@ -43,10 +43,10 @@ struct ColorsDemo {
         
         didSet {
             
-            self.palettes.refetch(
+//            self.palettes.refetch(
-                self.filter.whereClause(),
+//                self.filter.whereClause(),
-                OrderBy<Palette>(.ascending(\.hue))
+//                OrderBy<Palette>(.ascending(\.hue))
-            )
+//            )
         }
     }
     
@@ -73,9 +73,9 @@ struct ColorsDemo {
         return dataStack
     }()
     
-    static let palettes: ListMonitor<Palette> = {
+    static let palettes: LiveList<Palette> = {
 
-        return ColorsDemo.stack.monitorSectionedList(
+        return ColorsDemo.stack.liveList(
             From<Palette>()
                 .sectionBy(\.colorName)
                 .orderBy(.ascending(\.hue))
@@ -86,15 +86,7 @@ struct ColorsDemo {
 
 // MARK: - ListObserverDemoViewController
 
-class ListObserverDemoViewController: UITableViewController, ListSectionObserver {
+class ListObserverDemoViewController: UITableViewController {
-    
-    // MARK: NSObject
-    
-    deinit {
-        
-        ColorsDemo.palettes.removeObserver(self)
-    }
-    
     
     // MARK: UIViewController
 
@@ -133,9 +125,25 @@ class ListObserverDemoViewController: UITableViewController, ListSectionObserver
         ]
         self.filterBarButton = filterBarButton
 
-        ColorsDemo.palettes.addObserver(self)
+        self.dataSource = DiffableDataSource.TableView<Palette>(
+            tableView: self.tableView,
+            dataStack: ColorsDemo.stack,
+            cellProvider: { (tableView, indexPath, palette) in
                 
-        self.setTable(enabled: !ColorsDemo.palettes.isPendingRefetch)
+                let cell = tableView.dequeueReusableCell(withIdentifier: "PaletteTableViewCell") as! PaletteTableViewCell
+                cell.colorView?.backgroundColor = palette.color
+                cell.label?.text = palette.colorText
+                return cell
+            }
+        )
+        ColorsDemo.palettes.addObserver(self) { [weak self] (liveList, snapshot) in
+            
+            guard let self = self else {
+                
+                return
+            }
+            self.dataSource?.apply(snapshot, animatingDifferences: true)
+        }
     }
     
     override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
@@ -153,30 +161,6 @@ class ListObserverDemoViewController: UITableViewController, ListSectionObserver
     }
     
     
-    // MARK: UITableViewDataSource
-    
-    override func numberOfSections(in tableView: UITableView) -> Int {
-        
-        return ColorsDemo.palettes.numberOfSections()
-    }
-
-    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
-        
-        return ColorsDemo.palettes.numberOfObjects(in: section)
-    }
-    
-    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
-        
-        let cell = tableView.dequeueReusableCell(withIdentifier: "PaletteTableViewCell") as! PaletteTableViewCell
-        
-        let palette = ColorsDemo.palettes[indexPath]
-        cell.colorView?.backgroundColor = palette.color
-        cell.label?.text = palette.colorText
-        
-        return cell
-    }
-    
-    
     // MARK: UITableViewDelegate
     
     override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
@@ -185,7 +169,7 @@ class ListObserverDemoViewController: UITableViewController, ListSectionObserver
         
         self.performSegue(
             withIdentifier: "ObjectObserverDemoViewController",
-            sender: ColorsDemo.palettes[indexPath]
+            sender: ColorsDemo.palettes[indexPath: indexPath]?.object
         )
     }
     
@@ -194,11 +178,11 @@ class ListObserverDemoViewController: UITableViewController, ListSectionObserver
         switch editingStyle {
             
         case .delete:
-            let palette = ColorsDemo.palettes[indexPath]
+            let palette = ColorsDemo.palettes[indexPath: indexPath]
             ColorsDemo.stack.perform(
                 asynchronous: { (transaction) in
                     
-                    transaction.delete(palette)
+                    transaction.delete(palette?.object)
                 },
                 completion: { _ in }
             )
@@ -208,81 +192,16 @@ class ListObserverDemoViewController: UITableViewController, ListSectionObserver
         }
     }
     
-    override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
-        
-        return ColorsDemo.palettes.sectionInfo(at: section).name
-    }
-    
-    
-    // MARK: ListObserver
-    
-    func listMonitorWillChange(_ monitor: ListMonitor<Palette>) {
-        
-        self.tableView.beginUpdates()
-    }
-    
-    func listMonitorDidChange(_ monitor: ListMonitor<Palette>) {
-        
-        self.tableView.endUpdates()
-    }
-    
-    func listMonitorWillRefetch(_ monitor: ListMonitor<Palette>) {
-        
-        self.setTable(enabled: false)
-    }
-    
-    func listMonitorDidRefetch(_ monitor: ListMonitor<Palette>) {
-        
-        self.filterBarButton?.title = ColorsDemo.filter.rawValue
-        self.tableView.reloadData()
-        self.setTable(enabled: true)
-    }
-    
-    
-    // MARK: ListObjectObserver
-    
-    func listMonitor(_ monitor: ListMonitor<Palette>, didInsertObject object: Palette, toIndexPath indexPath: IndexPath) {
-        
-        self.tableView.insertRows(at: [indexPath], with: .automatic)
-    }
-    
-    func listMonitor(_ monitor: ListMonitor<Palette>, didDeleteObject object: Palette, fromIndexPath indexPath: IndexPath) {
-        
-        self.tableView.deleteRows(at: [indexPath], with: .automatic)
-    }
-    
-    func listMonitor(_ monitor: ListMonitor<Palette>, didUpdateObject object: Palette, atIndexPath indexPath: IndexPath) {
-        
-        if let cell = self.tableView.cellForRow(at: indexPath) as? PaletteTableViewCell {
-            
-            let palette = ColorsDemo.palettes[indexPath]
-            cell.colorView?.backgroundColor = palette.color
-            cell.label?.text = palette.colorText
-        }
-    }
-    
-    func listMonitor(_ monitor: ListMonitor<Palette>, didMoveObject object: Palette, fromIndexPath: IndexPath, toIndexPath: IndexPath) {
-
-        self.tableView.moveRow(at: fromIndexPath, to: toIndexPath)
-    }
-    
-    
-    // MARK: ListSectionObserver
-    
-    func listMonitor(_ monitor: ListMonitor<Palette>, didInsertSection sectionInfo: NSFetchedResultsSectionInfo, toSectionIndex sectionIndex: Int) {
-        
-        self.tableView.insertSections(IndexSet(integer: sectionIndex), with: .automatic)
-    }
-    
-    func listMonitor(_ monitor: ListMonitor<Palette>, didDeleteSection sectionInfo: NSFetchedResultsSectionInfo, fromSectionIndex sectionIndex: Int) {
-        
-        self.tableView.deleteSections(IndexSet(integer: sectionIndex), with: .automatic)
-    }
-    
     
     // MARK: Private
     
     private var filterBarButton: UIBarButtonItem?
+    private var dataSource: DiffableDataSource.TableView<Palette>?
+    
+    deinit {
+        
+        ColorsDemo.palettes.removeObserver(self)
+    }
     
     @IBAction private dynamic func resetBarButtonItemTouched(_ sender: AnyObject?) {
         
@@ -313,8 +232,6 @@ class ListObserverDemoViewController: UITableViewController, ListSectionObserver
     }
 
     @IBAction private dynamic func shuffleBarButtonItemTouched(_ sender: AnyObject?) {
-
-        self.setTable(enabled: false)
         ColorsDemo.stack.perform(
             asynchronous: { (transaction) in
 
@@ -324,28 +241,7 @@ class ListObserverDemoViewController: UITableViewController, ListSectionObserver
                     palette.colorName .= nil
                 }
             },
-            completion: { _ in
+            completion: { _ in }
-
-                self.setTable(enabled: true)
-            }
-        )
-    }
-    
-    private func setTable(enabled: Bool) {
-
-        tableView.isUserInteractionEnabled = enabled
-        UIView.animate(
-            withDuration: 0.2,
-            delay: 0,
-            options: .beginFromCurrentState,
-            animations: { () -> Void in
-                
-                if let tableView = self.tableView {
-                    
-                    tableView.alpha = enabled ? 1.0 : 0.5
-                }
-            },
-            completion: nil
         )
     }
 }

CoreStoreDemo/CoreStoreDemo/List and Object Observers Demo/ObserversViewController.swift

@@ -27,4 +27,20 @@ class ObserversViewController: UIViewController {
         alert.addAction(UIAlertAction(title: "OK", style: .cancel, handler: nil))
         self.present(alert, animated: true, completion: nil)
     }
+    
+    
+    // MARK: Private
+    
+    @IBOutlet private dynamic weak var topContainerView: UIView?
+    @IBOutlet private dynamic weak var bottomContainerView: UIView?
+    
+    @IBAction private dynamic func toggleTopContainerView() {
+        
+        self.topContainerView?.isHidden.toggle()
+    }
+    
+    @IBAction private dynamic func toggleBottomContainerView() {
+        
+        self.bottomContainerView?.isHidden.toggle()
+    }
 }

Sources/DataStack+DataSources.swift

@@ -31,7 +31,6 @@ import CoreData
 
 // MARK: - DataStack
 
-@available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *)
 extension DataStack {
 
     public func liveList<D>(_ from: From<D>, _ fetchClauses: FetchClause...) -> LiveList<D> {

Sources/DiffableDataSource.TableView.swift

@@ -29,79 +29,324 @@ import UIKit
 import CoreData
 
 
-//// MARK: - DiffableDataSource
+// MARK: - DiffableDataSource
-//
+
-//extension DiffableDataSource {
+extension DiffableDataSource {
-//
+
-//    // MARK: - TableView
+    // MARK: - TableView
-//
+
-//    public open class TableView<D: DynamicObject>: NSObject, UITableViewDataSource {
+    open class TableView<O: DynamicObject>: NSObject, UITableViewDataSource {
-//
+        
-//        // MARK: Public
+        // MARK: Open
-//
+
-//        public typealias ObjectType = D
+        @nonobjc
-//
+        open var defaultRowAnimation: UITableView.RowAnimation = .automatic
-//        public var defaultRowAnimation: UITableView.RowAnimation = .automatic
+        
-//
+
-//        public init(tableView: UITableView, cellProvider: @escaping (UITableView, IndexPath, ObjectType) -> UITableViewCell?) {
+        // MARK: Public
-//
+
-//            self.tableView = tableView
+        public typealias ObjectType = O
-//            self.cellProvider = cellProvider
+        
-//
+        @nonobjc
+        public init(tableView: UITableView, dataStack: DataStack, cellProvider: @escaping (UITableView, IndexPath, ObjectType) -> UITableViewCell?) {
+
+            self.tableView = tableView
+            self.cellProvider = cellProvider
+            self.dataStack = dataStack
+
+            super.init()
+            
 //            if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
 //
-//                self.rawDataSource = UITableViewDiffableDataSource<String, D.ObjectID>(
+//                self.rawDataSource = UITableViewDiffableDataSource<String, O.ObjectID>(
 //                    tableView: tableView,
-//                    cellProvider: { (tableView, indexPath, managedObjectID) -> UITableViewCell? in
+//                    cellProvider: { [weak self] (tableView, indexPath, objectID) -> UITableViewCell? in
 //
-//                        cellProvider(
+//                        guard let self = self else {
+//
+//                            return nil
+//                        }
+//                        guard let object = self.dataStack.fetchExisting(objectID) as O? else {
+//
+//                            return nil
+//                        }
+//                        return self.cellProvider(tableView, indexPath, object)
 //                    }
 //                )
 //            }
 //            else {
-//
+                
-//                self.rawDataSource = nil
+                self.rawDataSource = Internals.DiffableDataUIDispatcher<O>(dataStack: dataStack)
 //            }
-//
+
-//            super.init()
+            tableView.dataSource = self
-//
+        }
-//            tableView.dataSource = self
+
-//        }
+        public func apply(_ snapshot: ListSnapshot<ObjectType>, animatingDifferences: Bool = true) {
-//
+
-//        public func apply(_ snapshot: ListSnapshot<ObjectType>, animatingDifferences: Bool = true) {
+            let diffableSnapshot = snapshot.diffableSnapshot
-//
-//            let dataSource = UITableViewDiffableDataSource<String, D>.
 //            if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
 //
-//                self.rawDataSource! as! UITableViewDiffableDataSource<String, D>
+//                self.modernDataSource.apply(
-//
+//                    diffableSnapshot as! NSDiffableDataSourceSnapshot<String, NSManagedObjectID>,
+//                    animatingDifferences: animatingDifferences,
+//                    completion: nil
+//                )
 //            }
 //            else {
-//
+                
+                self.legacyDataSource.apply(
+                    diffableSnapshot as! Internals.DiffableDataSourceSnapshot,
+                    view: self.tableView,
+                    animatingDifferences: animatingDifferences,
+                    performUpdates: { tableView, changeset, setSections in
+                        
+                        tableView.reload(
+                            using: changeset,
+                            with: self.defaultRowAnimation,
+                            setData: setSections
+                        )
+                    }
+                )
 //            }
-//            core.apply(
+        }
-//                snapshot,
+
-//                view: tableView,
+        public func itemIdentifier(for indexPath: IndexPath) -> O.ObjectID? {
-//                animatingDifferences: animatingDifferences,
+            
-//                performUpdates: { tableView, changeset, setSections in
+//            if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
-//                    tableView.reload(using: changeset, with: self.defaultRowAnimation, setData: setSections)
-//            })
-//        }
 //
+//                return self.modernDataSource.itemIdentifier(for: indexPath)
+//            }
+//            else {
+             
+                return self.legacyDataSource.itemIdentifier(for: indexPath)
+//            }
+        }
+
+        public func indexPath(for itemIdentifier: O.ObjectID) -> IndexPath? {
+            
+//            if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
 //
-//        // MARK: Private
+//                return self.modernDataSource.indexPath(for: itemIdentifier)
+//            }
+//            else {
+             
+                return self.legacyDataSource.indexPath(for: itemIdentifier)
+//            }
+        }
+        
+        
+        // MARK: - UITableViewDataSource
+
+        @objc
+        public dynamic func numberOfSections(in tableView: UITableView) -> Int {
+            
+//            if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
 //
-//        private weak var tableView: UITableView?
+//                return self.modernDataSource.numberOfSections(in: tableView)
-//        private let cellProvider: (UITableView, IndexPath, ObjectType) -> UITableViewCell?
+//            }
-//        private let rawDataSource: Any?
+//            else {
+             
+                return self.legacyDataSource.numberOfSections()
+//            }
+        }
+
+        @objc
+        public dynamic func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
+            
+//            if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
 //
+//                return self.modernDataSource.tableView(tableView, numberOfRowsInSection: section)
+//            }
+//            else {
+             
+                return self.legacyDataSource.numberOfItems(inSection: section)
+//            }
+        }
+
+        @objc
+        open dynamic func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
+            
+//            if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
+//
+//                return self.modernDataSource.snapshot().sectionIdentifiers[section]
+//            }
+//            else {
+
+                return self.legacyDataSource.sectionIdentifier(inSection: section)
+//            }
+        }
+
+        @objc
+        open dynamic func tableView(_ tableView: UITableView, titleForFooterInSection section: Int) -> String? {
+            
+//            if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
+//
+//                return self.modernDataSource.tableView(tableView, titleForFooterInSection: section)
+//            }
+//            else {
+
+                return nil
+//            }
+        }
+        
+        @objc
+        open dynamic func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
+            
+//            if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
+//
+//                return self.modernDataSource.tableView(tableView, cellForRowAt: indexPath)
+//            }
+//            else {
+             
+                guard let objectID = self.legacyDataSource.itemIdentifier(for: indexPath) else {
+                    
+                    Internals.abort("Object at \(Internals.typeName(IndexPath.self)) \(indexPath) already removed from list")
+                }
+                guard let object = self.dataStack.fetchExisting(objectID) as O? else {
+                    
+                    Internals.abort("Object at \(Internals.typeName(IndexPath.self)) \(indexPath) has been deleted")
+                }
+                guard let cell = self.cellProvider(tableView, indexPath, object) else {
+                    
+                    Internals.abort("\(Internals.typeName(UITableViewDataSource.self)) returned a `nil` cell for \(Internals.typeName(IndexPath.self)) \(indexPath)")
+                }
+                return cell
+//            }
+        }
+
+
+        // MARK: Private
+
+        private weak var tableView: UITableView?
+        
+        private let dataStack: DataStack
+        private let cellProvider: (UITableView, IndexPath, ObjectType) -> UITableViewCell?
+        private var rawDataSource: Any!
+        
 //        @available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *)
-//        private var diffableDataSource: UITableViewDiffableDataSource<String, D.ObjectID> {
+//        private var modernDataSource: UITableViewDiffableDataSource<String, O.ObjectID> {
 //
-//            return self.rawDataSource! as! UITableViewDiffableDataSource<String, D.ObjectID>
+//            return self.rawDataSource as! UITableViewDiffableDataSource<String, O.ObjectID>
 //        }
-//    }
+        
-//}
+        private var legacyDataSource: Internals.DiffableDataUIDispatcher<O> {
+            
+            return self.rawDataSource as! Internals.DiffableDataUIDispatcher<O>
+        }
+    }
+}
+
+
+// MARK: - UITableView
+
+extension UITableView {
+
+    // MARK: FilePrivate
+    
+    @nonobjc
+    fileprivate func reload<C, O>(
+        using stagedChangeset: Internals.DiffableDataUIDispatcher<O>.StagedChangeset<C>,
+        with animation: @autoclosure () -> RowAnimation,
+        interrupt: ((Internals.DiffableDataUIDispatcher<O>.Changeset<C>) -> Bool)? = nil,
+        setData: (C) -> Void
+    ) {
+        
+        self.reload(
+            using: stagedChangeset,
+            deleteSectionsAnimation: animation(),
+            insertSectionsAnimation: animation(),
+            reloadSectionsAnimation: animation(),
+            deleteRowsAnimation: animation(),
+            insertRowsAnimation: animation(),
+            reloadRowsAnimation: animation(),
+            interrupt: interrupt,
+            setData: setData
+        )
+    }
+    
+    @nonobjc
+    fileprivate func reload<C, O>(
+        using stagedChangeset: Internals.DiffableDataUIDispatcher<O>.StagedChangeset<C>,
+        deleteSectionsAnimation: @autoclosure () -> RowAnimation,
+        insertSectionsAnimation: @autoclosure () -> RowAnimation,
+        reloadSectionsAnimation: @autoclosure () -> RowAnimation,
+        deleteRowsAnimation: @autoclosure () -> RowAnimation,
+        insertRowsAnimation: @autoclosure () -> RowAnimation,
+        reloadRowsAnimation: @autoclosure () -> RowAnimation,
+        interrupt: ((Internals.DiffableDataUIDispatcher<O>.Changeset<C>) -> Bool)? = nil,
+        setData: (C) -> Void
+    ) {
+        
+        if case .none = window, let data = stagedChangeset.last?.data {
+            
+            setData(data)
+            self.reloadData()
+            return
+        }
+        for changeset in stagedChangeset {
+            
+            if let interrupt = interrupt, interrupt(changeset), let data = stagedChangeset.last?.data {
+                
+                setData(data)
+                self.reloadData()
+                return
+            }
+            self.cs_performBatchUpdates {
+                
+                setData(changeset.data)
+
+                if !changeset.sectionDeleted.isEmpty {
+                    
+                    self.deleteSections(IndexSet(changeset.sectionDeleted), with: deleteSectionsAnimation())
+                }
+                if !changeset.sectionInserted.isEmpty {
+                    
+                    self.insertSections(IndexSet(changeset.sectionInserted), with: insertSectionsAnimation())
+                }
+                if !changeset.sectionUpdated.isEmpty {
+                    
+                    self.reloadSections(IndexSet(changeset.sectionUpdated), with: reloadSectionsAnimation())
+                }
+                for (source, target) in changeset.sectionMoved {
+                    
+                    self.moveSection(source, toSection: target)
+                }
+                if !changeset.elementDeleted.isEmpty {
+                    
+                    self.deleteRows(at: changeset.elementDeleted.map { IndexPath(row: $0.element, section: $0.section) }, with: deleteRowsAnimation())
+                }
+                if !changeset.elementInserted.isEmpty {
+                    
+                    self.insertRows(at: changeset.elementInserted.map { IndexPath(row: $0.element, section: $0.section) }, with: insertRowsAnimation())
+                }
+                if !changeset.elementUpdated.isEmpty {
+                    
+                    self.reloadRows(at: changeset.elementUpdated.map { IndexPath(row: $0.element, section: $0.section) }, with: reloadRowsAnimation())
+                }
+                for (source, target) in changeset.elementMoved {
+                    
+                    self.moveRow(at: IndexPath(row: source.element, section: source.section), to: IndexPath(row: target.element, section: target.section))
+                }
+            }
+        }
+    }
+
+    @nonobjc
+    private func cs_performBatchUpdates(_ updates: () -> Void) {
+        
+        if #available(iOS 11.0, tvOS 11.0, *) {
+            
+            self.performBatchUpdates(updates)
+        }
+        else {
+            
+            self.beginUpdates()
+            updates()
+            self.endUpdates()
+        }
+    }
+}
 
 
 #endif

Sources/Differentiable.swift

@@ -0,0 +1,62 @@
+//
+//  Differentiable.swift
+//  CoreStore
+//
+//  Copyright © 2018 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+import Foundation
+
+
+// MARK: - Differentiable
+
+@usableFromInline
+internal protocol Differentiable {
+
+    associatedtype DifferenceIdentifier: Hashable
+
+    var differenceIdentifier: DifferenceIdentifier { get }
+
+    func isContentEqual(to source: Self) -> Bool
+}
+
+extension Differentiable where Self: AnyObject {
+
+    // MARK: Internal
+    
+    internal var differenceIdentifier: ObjectIdentifier {
+    
+        return .init(self)
+    }
+}
+
+
+// MARK: - DifferentiableSection
+
+@usableFromInline
+internal protocol DifferentiableSection: Differentiable {
+    
+    associatedtype Collection: Swift.Collection where Collection.Element: Differentiable
+    
+    var elements: Collection { get }
+
+    init<S: Sequence>(source: Self, elements: S) where S.Element == Collection.Element
+}

Sources/Internals.Closure.swift

@@ -0,0 +1,54 @@
+//
+//  Internals.Closure.swift
+//  CoreStore
+//
+//  Copyright © 2018 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+import Foundation
+
+
+// MARK: - Internals
+
+extension Internals {
+    
+    // MARK: - Closure
+    
+    internal final class Closure<T, U> {
+        
+        // MARK: FilePrivate
+        
+        internal init(_ closure: @escaping (T) -> U) {
+            
+            self.closure = closure
+        }
+        
+        internal func invoke(with argument: T) -> U {
+            
+            return self.closure(argument)
+        }
+        
+        
+        // MARK: Private
+        
+        private let closure: (T) -> U
+    }
+}

Sources/Internals.DiffableDataSourceSnapshot.swift

@@ -52,6 +52,18 @@ extension Internals {
             self.structure = .init(sections: sections)
         }
         
+        var sections: [Section] {
+            
+            get {
+                
+                return self.structure.sections
+            }
+            set {
+                
+                self.structure.sections = newValue
+            }
+        }
+
 
         // MARK: DiffableDataSourceSnapshotProtocol
 
@@ -186,48 +198,66 @@ extension Internals {
         private var structure: BackingStructure
 
 
-        // MARK: - ItemStateID
+        // MARK: - Section
 
-        internal struct ItemStateID: Identifiable, Equatable {
+        internal struct Section: DifferentiableSection, Equatable {
 
-            let stateTag: UUID
+            var isReloaded: Bool
 
-            init(id: NSManagedObjectID, stateTag: UUID) {
+            init(differenceIdentifier: String, items: [Item] = [], isReloaded: Bool = false) {
                 
-                self.id = id
+                self.differenceIdentifier = differenceIdentifier
-                self.stateTag = stateTag
+                self.elements = items
+                self.isReloaded = isReloaded
             }
 
-            func isContentEqual(to source: ItemStateID) -> Bool {
+            // MARK: Differentiable
 
-                return self.id == source.id && self.stateTag == source.stateTag
+            let differenceIdentifier: String
+
+            func isContentEqual(to source: Section) -> Bool {
+
+                return !self.isReloaded
+                    && self.differenceIdentifier == source.differenceIdentifier
             }
             
-            // MARK: Identifiable
             
-            let id: NSManagedObjectID
+            // MARK: DifferentiableSection
+            
+            var elements: [Item] = []
+
+            init<S: Sequence>(source: Section, elements: S) where S.Element == Item {
+
+                self.init(
+                    differenceIdentifier: source.differenceIdentifier,
+                    items: Array(elements),
+                    isReloaded: source.isReloaded
+                )
+            }
         }
 
 
-        // MARK: - SectionStateID
+        // MARK: - Item
 
-        internal struct SectionStateID: Identifiable, Equatable {
+        internal struct Item: Differentiable, Equatable {
 
-            let stateTag: UUID
+            var isReloaded: Bool
 
-            init(id: String, stateTag: UUID) {
+            init(differenceIdentifier: NSManagedObjectID, isReloaded: Bool = false) {
-                self.id = id
+
-                self.stateTag = stateTag
+                self.differenceIdentifier = differenceIdentifier
+                self.isReloaded = isReloaded
             }
 
-            func isContentEqual(to source: SectionStateID) -> Bool {
+            // MARK: Differentiable
 
-                return self.id == source.id && self.stateTag == source.stateTag
+            let differenceIdentifier: NSManagedObjectID
+
+            func isContentEqual(to source: Item) -> Bool {
+
+                return !self.isReloaded
+                    && self.differenceIdentifier == source.differenceIdentifier
             }
-
-            // MARK: Identifiable
-
-            let id: String
         }
 
 
@@ -249,22 +279,22 @@ extension Internals {
                 self.sections = sections.map {
 
                     Section(
-                        id: $0.name,
+                        differenceIdentifier: $0.name,
                         items: $0.objects?
                             .compactMap({ ($0 as? NSManagedObject)?.objectID })
-                            .map({ Item(id: $0) }) ?? []
+                            .map({ Item(differenceIdentifier: $0) }) ?? []
                     )
                 }
             }
 
             var allSectionIDs: [String] {
 
-                return self.sections.map({ $0.id })
+                return self.sections.map({ $0.differenceIdentifier })
             }
 
             var allItemIDs: [NSManagedObjectID] {
 
-                return self.sections.lazy.flatMap({ $0.elements }).map({ $0.id })
+                return self.sections.lazy.flatMap({ $0.elements }).map({ $0.differenceIdentifier })
             }
 
             func items(in sectionID: String) -> [NSManagedObjectID] {
@@ -273,12 +303,12 @@ extension Internals {
 
                     Internals.abort("Section \"\(sectionID)\" does not exist")
                 }
-                return self.sections[sectionIndex].elements.map({ $0.id })
+                return self.sections[sectionIndex].elements.map({ $0.differenceIdentifier })
             }
 
             func section(containing itemID: NSManagedObjectID) -> String? {
 
-                return self.itemPositionMap()[itemID]?.section.id
+                return self.itemPositionMap()[itemID]?.section.differenceIdentifier
             }
 
             mutating func append(itemIDs: [NSManagedObjectID], to sectionID: String?) {
@@ -301,7 +331,7 @@ extension Internals {
                     }
                     index = section.index(before: section.endIndex)
                 }
-                let items = itemIDs.lazy.map({ Item(id: $0) })
+                let items = itemIDs.lazy.map({ Item(differenceIdentifier: $0) })
                 self.sections[index].elements.append(contentsOf: items)
             }
 
@@ -311,7 +341,7 @@ extension Internals {
 
                     Internals.abort("Item \(beforeItemID) does not exist")
                 }
-                let items = itemIDs.lazy.map({ Item(id: $0) })
+                let items = itemIDs.lazy.map({ Item(differenceIdentifier: $0) })
                 self.sections[itemPosition.sectionIndex].elements
                     .insert(contentsOf: items, at: itemPosition.itemRelativeIndex)
             }
@@ -324,7 +354,7 @@ extension Internals {
                 }
                 let itemIndex = self.sections[itemPosition.sectionIndex].elements
                     .index(after: itemPosition.itemRelativeIndex)
-                let items = itemIDs.lazy.map({ Item(id: $0) })
+                let items = itemIDs.lazy.map({ Item(differenceIdentifier: $0) })
                 self.sections[itemPosition.sectionIndex].elements
                     .insert(contentsOf: items, at: itemIndex)
             }
@@ -406,7 +436,7 @@ extension Internals {
 
             mutating func append(sectionIDs: [String]) {
 
-                let newSections = sectionIDs.lazy.map({ Section(id: $0) })
+                let newSections = sectionIDs.lazy.map({ Section(differenceIdentifier: $0) })
                 self.sections.append(contentsOf: newSections)
             }
 
@@ -416,7 +446,7 @@ extension Internals {
 
                     Internals.abort("Section \"\(beforeSectionID)\" does not exist")
                 }
-                let newSections = sectionIDs.lazy.map({ Section(id: $0) })
+                let newSections = sectionIDs.lazy.map({ Section(differenceIdentifier: $0) })
                 self.sections.insert(contentsOf: newSections, at: sectionIndex)
             }
 
@@ -427,7 +457,7 @@ extension Internals {
                     Internals.abort("Section \"\(afterSectionID)\" does not exist")
                 }
                 let sectionIndex = self.sections.index(after: beforeIndex)
-                let newSections = sectionIDs.lazy.map({ Section(id: $0) })
+                let newSections = sectionIDs.lazy.map({ Section(differenceIdentifier: $0) })
                 self.sections.insert(contentsOf: newSections, at: sectionIndex)
             }
 
@@ -481,11 +511,9 @@ extension Internals {
 
             // MARK: Private
 
-            private static let zeroUUID: UUID = .init(uuid: (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0))
-
             private func sectionIndex(of sectionID: String) -> Array<Section>.Index? {
 
-                return self.sections.firstIndex(where: { $0.id == sectionID })
+                return self.sections.firstIndex(where: { $0.differenceIdentifier == sectionID })
             }
 
             @discardableResult
@@ -515,7 +543,7 @@ extension Internals {
 
                     for (itemRelativeIndex, item) in section.element.elements.enumerated() {
 
-                        result[item.id] = ItemPosition(
+                        result[item.differenceIdentifier] = ItemPosition(
                             item: item,
                             itemRelativeIndex: itemRelativeIndex,
                             section: section.element,
@@ -526,58 +554,6 @@ extension Internals {
             }
 
 
-            // MARK: - Item
-
-            fileprivate struct Item: Identifiable, Equatable {
-
-                var isReloaded: Bool
-
-                init(id: NSManagedObjectID, isReloaded: Bool = false) {
-
-                    self.id = id
-                    self.isReloaded = isReloaded
-                }
-
-                func isContentEqual(to source: Item) -> Bool {
-
-                    return !self.isReloaded && self.id == source.id
-                }
-
-                // MARK: Identifiable
-
-                let id: NSManagedObjectID
-            }
-
-
-            // MARK: - Section
-
-            fileprivate struct Section: Identifiable, Equatable {
-
-                var elements: [Item] = []
-                var isReloaded: Bool
-
-                init(id: String, items: [Item] = [], isReloaded: Bool = false) {
-                    self.id = id
-                    self.elements = items
-                    self.isReloaded = isReloaded
-                }
-
-                init<S: Sequence>(source: Section, elements: S) where S.Element == Item {
-
-                    self.init(id: source.id, items: Array(elements), isReloaded: source.isReloaded)
-                }
-
-                func isContentEqual(to source: Section) -> Bool {
-
-                    return !self.isReloaded && self.id == source.id
-                }
-
-                // MARK: Identifiable
-
-                let id: String
-            }
-
-
             // MARK: - ItemPosition
 
             fileprivate struct ItemPosition {
@@ -595,73 +571,7 @@ 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 {
+extension NSDiffableDataSourceSnapshot: DiffableDataSourceSnapshotProtocol where SectionIdentifierType == String, 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.DiffableDataUIDispatcher.Changeset.swift

@@ -0,0 +1,141 @@
+//
+//  Internals.DiffableDataUIDispatcher.Changeset.swift
+//  CoreStore
+//
+//  Copyright © 2018 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+#if canImport(UIKit) || canImport(AppKit)
+
+import Foundation
+
+
+// MARK: - Internals.DiffableDataUIDispatcher
+
+extension Internals.DiffableDataUIDispatcher {
+    
+    // MARK: - ChangeSet
+    
+    internal struct Changeset<C: Collection>: Equatable where C: Equatable {
+        
+        var data: C
+        var sectionDeleted: [Int]
+        var sectionInserted: [Int]
+        var sectionUpdated: [Int]
+        var sectionMoved: [(source: Int, target: Int)]
+
+        var elementDeleted: [ElementPath]
+        var elementInserted: [ElementPath]
+        var elementUpdated: [ElementPath]
+        var elementMoved: [(source: ElementPath, target: ElementPath)]
+
+        @inlinable
+        init(
+            data: C,
+            sectionDeleted: [Int] = [],
+            sectionInserted: [Int] = [],
+            sectionUpdated: [Int] = [],
+            sectionMoved: [(source: Int, target: Int)] = [],
+            elementDeleted: [ElementPath] = [],
+            elementInserted: [ElementPath] = [],
+            elementUpdated: [ElementPath] = [],
+            elementMoved: [(source: ElementPath, target: ElementPath)] = []
+        ) {
+            self.data = data
+            self.sectionDeleted = sectionDeleted
+            self.sectionInserted = sectionInserted
+            self.sectionUpdated = sectionUpdated
+            self.sectionMoved = sectionMoved
+            self.elementDeleted = elementDeleted
+            self.elementInserted = elementInserted
+            self.elementUpdated = elementUpdated
+            self.elementMoved = elementMoved
+        }
+
+        @inlinable
+        var sectionChangeCount: Int {
+            
+            return self.sectionDeleted.count
+                + self.sectionInserted.count
+                + self.sectionUpdated.count
+                + self.sectionMoved.count
+        }
+
+        @inlinable
+        var elementChangeCount: Int {
+            
+            return self.elementDeleted.count
+                + self.elementInserted.count
+                + self.elementUpdated.count
+                + self.elementMoved.count
+        }
+
+        @inlinable
+        var changeCount: Int {
+            
+            return self.sectionChangeCount + self.elementChangeCount
+        }
+
+        @inlinable
+        var hasSectionChanges: Bool {
+            
+            return self.sectionChangeCount > 0
+        }
+
+        @inlinable
+        var hasElementChanges: Bool {
+            
+            return self.elementChangeCount > 0
+        }
+
+        @inlinable
+        var hasChanges: Bool {
+            
+            return self.changeCount > 0
+        }
+        
+        
+        // MARK: Equatable
+        
+        static func == (lhs: Changeset, rhs: Changeset) -> Bool {
+            return lhs.data == rhs.data
+                && Set(lhs.sectionDeleted) == Set(rhs.sectionDeleted)
+                && Set(lhs.sectionInserted) == Set(rhs.sectionInserted)
+                && Set(lhs.sectionUpdated) == Set(rhs.sectionUpdated)
+                && Set(lhs.sectionMoved.map(HashablePair.init)) == Set(rhs.sectionMoved.map(HashablePair.init))
+                && Set(lhs.elementDeleted) == Set(rhs.elementDeleted)
+                && Set(lhs.elementInserted) == Set(rhs.elementInserted)
+                && Set(lhs.elementUpdated) == Set(rhs.elementUpdated)
+                && Set(lhs.elementMoved.map(HashablePair.init)) == Set(rhs.elementMoved.map(HashablePair.init))
+        }
+        
+        
+        // MARK: - HashablePair
+        
+        private struct HashablePair<H: Hashable>: Hashable {
+            
+            let first: H
+            let second: H
+        }
+    }
+}
+
+#endif

Sources/Internals.DiffableDataUIDispatcher.DiffResult.swift

@@ -0,0 +1,320 @@
+//
+//  Internals.DiffableDataUIDispatcher.DiffResult.swift
+//  CoreStore
+//
+//  Copyright © 2018 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+#if canImport(UIKit) || canImport(AppKit)
+
+import Foundation
+
+
+// MARK: - Internals.DiffableDataUIDispatcher
+
+extension Internals.DiffableDataUIDispatcher {
+    
+    // MARK: - DiffResult
+    
+    @usableFromInline
+    internal struct DiffResult<Index> {
+        
+        @usableFromInline
+        internal let deleted: [Index]
+        @usableFromInline
+        internal let inserted: [Index]
+        @usableFromInline
+        internal let updated: [Index]
+        @usableFromInline
+        internal let moved: [(source: Index, target: Index)]
+        @usableFromInline
+        internal let sourceTraces: ContiguousArray<Trace<Int>>
+        @usableFromInline
+        internal let targetReferences: ContiguousArray<Int?>
+        
+        @inlinable
+        @discardableResult
+        static func diff<E: Differentiable>(
+            source: ContiguousArray<E>,
+            target: ContiguousArray<E>,
+            useTargetIndexForUpdated: Bool,
+            mapIndex: (Int) -> Index,
+            updatedElementsPointer: UnsafeMutablePointer<ContiguousArray<E>>? = nil,
+            notDeletedElementsPointer: UnsafeMutablePointer<ContiguousArray<E>>? = nil
+        ) -> DiffResult<Index> {
+            
+            var deleted = [Index]()
+            var inserted = [Index]()
+            var updated = [Index]()
+            var moved = [(source: Index, target: Index)]()
+            
+            var sourceTraces = ContiguousArray<Trace<Int>>()
+            var sourceIdentifiers = ContiguousArray<E.DifferenceIdentifier>()
+            var targetReferences = ContiguousArray<Int?>(repeating: nil, count: target.count)
+            
+            sourceTraces.reserveCapacity(source.count)
+            sourceIdentifiers.reserveCapacity(source.count)
+            
+            for sourceElement in source {
+                
+                sourceTraces.append(Trace())
+                sourceIdentifiers.append(sourceElement.differenceIdentifier)
+            }
+            sourceIdentifiers.withUnsafeBufferPointer { bufferPointer in
+                
+                var sourceOccurrencesTable = [TableKey<E.DifferenceIdentifier>: Occurrence](minimumCapacity: source.count)
+                
+                for sourceIndex in sourceIdentifiers.indices {
+                    
+                    let pointer = bufferPointer.baseAddress!.advanced(by: sourceIndex)
+                    let key = TableKey(pointer: pointer)
+                    
+                    switch sourceOccurrencesTable[key] {
+                    case .none:
+                        sourceOccurrencesTable[key] = .unique(index: sourceIndex)
+                        
+                    case .unique(let otherIndex)?:
+                        let reference = IndicesReference([otherIndex, sourceIndex])
+                        sourceOccurrencesTable[key] = .duplicate(reference: reference)
+                        
+                    case .duplicate(let reference)?:
+                        reference.push(sourceIndex)
+                    }
+                }
+                for targetIndex in target.indices {
+                    
+                    var targetIdentifier = target[targetIndex].differenceIdentifier
+                    let key = TableKey(pointer: &targetIdentifier)
+                    
+                    switch sourceOccurrencesTable[key] {
+                        
+                    case .none:
+                        break
+                        
+                    case .unique(let sourceIndex)?:
+                        if case .none = sourceTraces[sourceIndex].reference {
+                            
+                            targetReferences[targetIndex] = sourceIndex
+                            sourceTraces[sourceIndex].reference = targetIndex
+                        }
+                        
+                    case .duplicate(let reference)?:
+                        if let sourceIndex = reference.next() {
+                            
+                            targetReferences[targetIndex] = sourceIndex
+                            sourceTraces[sourceIndex].reference = targetIndex
+                        }
+                    }
+                }
+            }
+            
+            var offsetByDelete = 0
+            var untrackedSourceIndex: Int? = 0
+            
+            for sourceIndex in source.indices {
+                
+                sourceTraces[sourceIndex].deleteOffset = offsetByDelete
+                
+                if let targetIndex = sourceTraces[sourceIndex].reference {
+                    
+                    let targetElement = target[targetIndex]
+                    updatedElementsPointer?.pointee.append(targetElement)
+                    notDeletedElementsPointer?.pointee.append(targetElement)
+                }
+                else {
+                    
+                    let sourceElement = source[sourceIndex]
+                    deleted.append(mapIndex(sourceIndex))
+                    sourceTraces[sourceIndex].isTracked = true
+                    offsetByDelete += 1
+                    updatedElementsPointer?.pointee.append(sourceElement)
+                }
+            }
+            for targetIndex in target.indices {
+                
+                untrackedSourceIndex = untrackedSourceIndex.flatMap { index in
+                    
+                    sourceTraces.suffix(from: index).firstIndex { !$0.isTracked }
+                }
+                if let sourceIndex = targetReferences[targetIndex] {
+                    
+                    sourceTraces[sourceIndex].isTracked = true
+                    
+                    let sourceElement = source[sourceIndex]
+                    let targetElement = target[targetIndex]
+                    
+                    if !targetElement.isContentEqual(to: sourceElement) {
+                        
+                        updated.append(mapIndex(useTargetIndexForUpdated ? targetIndex : sourceIndex))
+                    }
+                    if sourceIndex != untrackedSourceIndex {
+                        
+                        let deleteOffset = sourceTraces[sourceIndex].deleteOffset
+                        moved.append((source: mapIndex(sourceIndex - deleteOffset), target: mapIndex(targetIndex)))
+                    }
+                }
+                else {
+                    
+                    inserted.append(mapIndex(targetIndex))
+                }
+            }
+            return DiffResult(
+                deleted: deleted,
+                inserted: inserted,
+                updated: updated,
+                moved: moved,
+                sourceTraces: sourceTraces,
+                targetReferences: targetReferences
+            )
+        }
+        
+        
+        // MARK: Private
+        
+        @inlinable
+        internal init(
+            deleted: [Index] = [],
+            inserted: [Index] = [],
+            updated: [Index] = [],
+            moved: [(source: Index, target: Index)] = [],
+            sourceTraces: ContiguousArray<Trace<Int>>,
+            targetReferences: ContiguousArray<Int?>
+        ) {
+            
+            self.deleted = deleted
+            self.inserted = inserted
+            self.updated = updated
+            self.moved = moved
+            self.sourceTraces = sourceTraces
+            self.targetReferences = targetReferences
+        }
+        
+        
+        // MARK: - Trace
+        
+        @usableFromInline
+        internal struct Trace<Index> {
+            
+            @usableFromInline
+            internal var reference: Index?
+            
+            @usableFromInline
+            internal var deleteOffset = 0
+            
+            @usableFromInline
+            internal var isTracked = false
+            
+            @inlinable
+            init() {}
+        }
+        
+        
+        // MARK: - Occurrence
+        
+        @usableFromInline
+        internal enum Occurrence {
+            
+            case unique(index: Int)
+            case duplicate(reference: IndicesReference)
+        }
+        
+        
+        // MARK: - IndicesReference
+        
+        @usableFromInline
+        internal final class IndicesReference {
+            
+            @usableFromInline
+            internal var indices: ContiguousArray<Int>
+            
+            @usableFromInline
+            internal var position = 0
+            
+            @inlinable
+            internal init(_ indices: ContiguousArray<Int>) {
+                
+                self.indices = indices
+            }
+            
+            @inlinable
+            internal func push(_ index: Int) {
+                
+                self.indices.append(index)
+            }
+            
+            @inlinable
+            internal func next() -> Int? {
+                
+                guard self.position < self.indices.endIndex else {
+                    
+                    return nil
+                }
+                defer {
+                    
+                    self.position += 1
+                }
+                return self.indices[self.position]
+            }
+        }
+        
+        
+        // MARK: - TableKey
+        
+        @usableFromInline
+        internal struct TableKey<T: Hashable>: Hashable {
+            
+            @usableFromInline
+            internal let pointeeHashValue: Int
+            
+            @usableFromInline
+            internal let pointer: UnsafePointer<T>
+            
+            @inlinable
+            internal init(pointer: UnsafePointer<T>) {
+                
+                self.pointeeHashValue = pointer.pointee.hashValue
+                self.pointer = pointer
+            }
+            
+            
+            // MARK: Equatable
+            
+            @inlinable
+            internal static func == (lhs: TableKey, rhs: TableKey) -> Bool {
+                
+                return lhs.pointeeHashValue == rhs.pointeeHashValue
+                    && (lhs.pointer.distance(to: rhs.pointer) == 0
+                        || lhs.pointer.pointee == rhs.pointer.pointee)
+            }
+            
+            
+            // MARK: Hashable
+            
+            @inlinable
+            internal func hash(into hasher: inout Hasher) {
+                
+                hasher.combine(pointeeHashValue)
+            }
+        }
+    }
+}
+
+#endif

Sources/Internals.DiffableDataUIDispatcher.StagedChangeset.swift

@@ -0,0 +1,516 @@
+//
+//  Internals.DiffableDataUIDispatcher.StagedChangeset.swift
+//  CoreStore
+//
+//  Copyright © 2018 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+#if canImport(UIKit) || canImport(AppKit)
+
+import Foundation
+
+
+// MARK: - Internals.DiffableDataUIDispatcher
+
+extension Internals.DiffableDataUIDispatcher {
+    
+    // MARK: - StagedChangeset
+
+    internal struct StagedChangeset<C: Collection>: ExpressibleByArrayLiteral, Equatable, RandomAccessCollection, RangeReplaceableCollection where C: Equatable {
+        
+        @usableFromInline
+        var changesets: ContiguousArray<Changeset<C>>
+
+        @inlinable
+        init<S: Sequence>(_ changesets: S) where S.Element == Changeset<C> {
+            
+            self.changesets = ContiguousArray(changesets)
+        }
+        
+        
+        // MARK: ExpressibleByArrayLiteral
+        
+        @inlinable
+        init(arrayLiteral elements: Changeset<C>...) {
+            
+            self.init(elements)
+        }
+        
+        
+        // MARK: Equatable
+
+        @inlinable
+        static func == (lhs: StagedChangeset, rhs: StagedChangeset) -> Bool {
+            
+            return lhs.changesets == rhs.changesets
+        }
+        
+        
+        // MARK: Sequence
+
+        typealias Element = Changeset<C>
+        
+        
+        // MARK: RandomAccessCollection
+
+        @inlinable
+        var startIndex: Int {
+            
+            return self.changesets.startIndex
+        }
+
+        @inlinable
+        var endIndex: Int {
+            
+            return self.changesets.endIndex
+        }
+
+        @inlinable
+        func index(after i: Int) -> Int {
+            
+            return self.changesets.index(after: i)
+        }
+
+        @inlinable
+        subscript(position: Int) -> Changeset<C> {
+            
+            get { return self.changesets[position] }
+            set { self.changesets[position] = newValue }
+        }
+        
+        
+        // MARK: RangeReplaceableCollection
+
+        @inlinable
+        init() {
+            
+            self.init([])
+        }
+
+        @inlinable
+        mutating func replaceSubrange<C2: Collection, R: RangeExpression>(_ subrange: R, with newElements: C2) where C2.Element == Changeset<C>, R.Bound == Int {
+            
+            self.changesets.replaceSubrange(subrange, with: newElements)
+        }
+    }
+}
+
+
+// MARK: - Internals.DiffableDataUIDispatcher.StagedChangeset where C: RangeReplaceableCollection, C.Element: Differentiable
+
+extension Internals.DiffableDataUIDispatcher.StagedChangeset where C: RangeReplaceableCollection, C.Element: Differentiable {
+    
+    @inlinable
+    internal init(source: C, target: C) {
+        
+        self.init(source: source, target: target, section: 0)
+    }
+    
+    @inlinable
+    internal init(source: C, target: C, section: Int) {
+        
+        typealias Changeset = Internals.DiffableDataUIDispatcher<O>.Changeset
+        typealias ElementPath = Internals.DiffableDataUIDispatcher<O>.ElementPath
+        typealias DiffResult = Internals.DiffableDataUIDispatcher<O>.DiffResult
+        
+        let sourceElements = ContiguousArray(source)
+        let targetElements = ContiguousArray(target)
+        if sourceElements.isEmpty && targetElements.isEmpty {
+            
+            self.init()
+            return
+        }
+        if !sourceElements.isEmpty && targetElements.isEmpty {
+            
+            self.init(
+                [
+                    Changeset(
+                        data: target,
+                        elementDeleted: sourceElements.indices.map {
+                            ElementPath(
+                                element: $0,
+                                section: section
+                            )
+                        }
+                    )
+                ]
+            )
+            return
+        }
+        if sourceElements.isEmpty && !targetElements.isEmpty {
+            
+            self.init(
+                [
+                    Changeset(
+                        data: target,
+                        elementInserted: targetElements.indices.map {
+                            ElementPath(
+                                element: $0,
+                                section: section
+                            )
+                        }
+                    )
+                ]
+            )
+            return
+        }
+        var firstStageElements = ContiguousArray<C.Element>()
+        var secondStageElements = ContiguousArray<C.Element>()
+        let result = DiffResult.diff(
+            source: sourceElements,
+            target: targetElements,
+            useTargetIndexForUpdated: false,
+            mapIndex: { ElementPath(element: $0, section: section) },
+            updatedElementsPointer: &firstStageElements,
+            notDeletedElementsPointer: &secondStageElements
+        )
+
+        var changesets = ContiguousArray<Changeset<C>>()
+        if !result.updated.isEmpty {
+            
+            changesets.append(
+                Changeset(
+                    data: C(firstStageElements),
+                    elementUpdated: result.updated
+                )
+            )
+        }
+        if !result.deleted.isEmpty {
+            
+            changesets.append(
+                Changeset(
+                    data: C(secondStageElements),
+                    elementDeleted: result.deleted
+                )
+            )
+        }
+        if !result.inserted.isEmpty || !result.moved.isEmpty {
+            
+            changesets.append(
+                Changeset(
+                    data: target,
+                    elementInserted: result.inserted,
+                    elementMoved: result.moved
+                )
+            )
+        }
+        if !changesets.isEmpty {
+            
+            let index = changesets.index(before: changesets.endIndex)
+            changesets[index].data = target
+        }
+        self.init(changesets)
+    }
+}
+
+
+// MARK: - Internals.DiffableDataUIDispatcher.StagedChangeset where C: RangeReplaceableCollection, C.Element: DifferentiableSection
+
+extension Internals.DiffableDataUIDispatcher.StagedChangeset where C: RangeReplaceableCollection, C.Element: DifferentiableSection {
+    
+    @inlinable
+    internal init(source: C, target: C) {
+        
+        typealias Section = C.Element
+        typealias SectionIdentifier = C.Element.DifferenceIdentifier
+        typealias Element = C.Element.Collection.Element
+        typealias ElementIdentifier = C.Element.Collection.Element.DifferenceIdentifier
+        
+        typealias Changeset = Internals.DiffableDataUIDispatcher<O>.Changeset
+        typealias ElementPath = Internals.DiffableDataUIDispatcher<O>.ElementPath
+        typealias DiffResult = Internals.DiffableDataUIDispatcher<O>.DiffResult
+        
+        typealias Trace = Internals.DiffableDataUIDispatcher<O>.DiffResult<Section>.Trace
+        typealias TableKey = Internals.DiffableDataUIDispatcher<O>.DiffResult<Section>.TableKey
+        typealias Occurrence = Internals.DiffableDataUIDispatcher<O>.DiffResult<Section>.Occurrence
+        typealias IndicesReference = Internals.DiffableDataUIDispatcher<O>.DiffResult<Section>.IndicesReference
+
+        let sourceSections = ContiguousArray(source)
+        let targetSections = ContiguousArray(target)
+
+        let contiguousSourceSections = ContiguousArray(sourceSections.map { ContiguousArray($0.elements) })
+        let contiguousTargetSections = ContiguousArray(targetSections.map { ContiguousArray($0.elements) })
+
+        var firstStageSections = sourceSections
+        var secondStageSections = ContiguousArray<Section>()
+        var thirdStageSections = ContiguousArray<Section>()
+        var fourthStageSections = ContiguousArray<Section>()
+
+        var sourceElementTraces = contiguousSourceSections.map { section in
+            
+            ContiguousArray(repeating: Trace<ElementPath>(), count: section.count)
+        }
+        var targetElementReferences = contiguousTargetSections.map { section in
+            
+            ContiguousArray<ElementPath?>(repeating: nil, count: section.count)
+        }
+
+        let flattenSourceCount = contiguousSourceSections.reduce(into: 0) { $0 += $1.count }
+        var flattenSourceIdentifiers = ContiguousArray<ElementIdentifier>()
+        var flattenSourceElementPaths = ContiguousArray<ElementPath>()
+
+        thirdStageSections.reserveCapacity(contiguousTargetSections.count)
+        fourthStageSections.reserveCapacity(contiguousTargetSections.count)
+
+        flattenSourceIdentifiers.reserveCapacity(flattenSourceCount)
+        flattenSourceElementPaths.reserveCapacity(flattenSourceCount)
+
+        let sectionResult = DiffResult.diff(
+            source: sourceSections,
+            target: targetSections,
+            useTargetIndexForUpdated: true,
+            mapIndex: { $0 }
+        )
+
+        var elementDeleted = [ElementPath]()
+        var elementInserted = [ElementPath]()
+        var elementUpdated = [ElementPath]()
+        var elementMoved = [(source: ElementPath, target: ElementPath)]()
+
+        for sourceSectionIndex in contiguousSourceSections.indices {
+            
+            for sourceElementIndex in contiguousSourceSections[sourceSectionIndex].indices {
+                
+                let sourceElementPath = ElementPath(element: sourceElementIndex, section: sourceSectionIndex)
+                let sourceElement = contiguousSourceSections[sourceElementPath]
+                flattenSourceIdentifiers.append(sourceElement.differenceIdentifier)
+                flattenSourceElementPaths.append(sourceElementPath)
+            }
+        }
+        flattenSourceIdentifiers.withUnsafeBufferPointer { bufferPointer in
+            
+            var sourceOccurrencesTable = [TableKey<ElementIdentifier>: Occurrence](minimumCapacity: flattenSourceCount)
+
+            for flattenSourceIndex in flattenSourceIdentifiers.indices {
+                let pointer = bufferPointer.baseAddress!.advanced(by: flattenSourceIndex)
+                let key = TableKey(pointer: pointer)
+
+                switch sourceOccurrencesTable[key] {
+                    
+                case .none:
+                    sourceOccurrencesTable[key] = .unique(index: flattenSourceIndex)
+
+                case .unique(let otherIndex)?:
+                    let reference = IndicesReference([otherIndex, flattenSourceIndex])
+                    sourceOccurrencesTable[key] = .duplicate(reference: reference)
+
+                case .duplicate(let reference)?:
+                    reference.push(flattenSourceIndex)
+                }
+            }
+
+            for targetSectionIndex in contiguousTargetSections.indices {
+                
+                let targetElements = contiguousTargetSections[targetSectionIndex]
+                for targetElementIndex in targetElements.indices {
+                    
+                    var targetIdentifier = targetElements[targetElementIndex].differenceIdentifier
+                    let key = TableKey(pointer: &targetIdentifier)
+
+                    switch sourceOccurrencesTable[key] {
+                        
+                    case .none:
+                        break
+
+                    case .unique(let flattenSourceIndex)?:
+                        let sourceElementPath = flattenSourceElementPaths[flattenSourceIndex]
+                        let targetElementPath = ElementPath(element: targetElementIndex, section: targetSectionIndex)
+                        if case .none = sourceElementTraces[sourceElementPath].reference {
+                            
+                            targetElementReferences[targetElementPath] = sourceElementPath
+                            sourceElementTraces[sourceElementPath].reference = targetElementPath
+                        }
+
+                    case .duplicate(let reference)?:
+                        if let flattenSourceIndex = reference.next() {
+                            
+                            let sourceElementPath = flattenSourceElementPaths[flattenSourceIndex]
+                            let targetElementPath = ElementPath(element: targetElementIndex, section: targetSectionIndex)
+                            targetElementReferences[targetElementPath] = sourceElementPath
+                            sourceElementTraces[sourceElementPath].reference = targetElementPath
+                        }
+                    }
+                }
+            }
+        }
+        for sourceSectionIndex in contiguousSourceSections.indices {
+            
+            let sourceSection = sourceSections[sourceSectionIndex]
+            let sourceElements = contiguousSourceSections[sourceSectionIndex]
+            var firstStageElements = sourceElements
+
+            if case .some = sectionResult.sourceTraces[sourceSectionIndex].reference {
+                
+                var offsetByDelete = 0
+                var secondStageElements = ContiguousArray<Element>()
+                for sourceElementIndex in sourceElements.indices {
+                    
+                    let sourceElementPath = ElementPath(element: sourceElementIndex, section: sourceSectionIndex)
+                    sourceElementTraces[sourceElementPath].deleteOffset = offsetByDelete
+
+                    if let targetElementPath = sourceElementTraces[sourceElementPath].reference,
+                        case .some = sectionResult.targetReferences[targetElementPath.section] {
+                        
+                        let targetElement = contiguousTargetSections[targetElementPath]
+                        firstStageElements[sourceElementIndex] = targetElement
+                        secondStageElements.append(targetElement)
+                        continue
+                    }
+                    elementDeleted.append(sourceElementPath)
+                    sourceElementTraces[sourceElementPath].isTracked = true
+                    offsetByDelete += 1
+                }
+
+                let secondStageSection = Section(source: sourceSection, elements: secondStageElements)
+                secondStageSections.append(secondStageSection)
+            }
+
+            let firstStageSection = Section(source: sourceSection, elements: firstStageElements)
+            firstStageSections[sourceSectionIndex] = firstStageSection
+        }
+        for targetSectionIndex in contiguousTargetSections.indices {
+            
+            guard let sourceSectionIndex = sectionResult.targetReferences[targetSectionIndex] else {
+                
+                thirdStageSections.append(targetSections[targetSectionIndex])
+                fourthStageSections.append(targetSections[targetSectionIndex])
+                continue
+            }
+
+            var untrackedSourceIndex: Int? = 0
+            let targetElements = contiguousTargetSections[targetSectionIndex]
+            let sectionDeleteOffset = sectionResult.sourceTraces[sourceSectionIndex].deleteOffset
+            let thirdStageSection = secondStageSections[sourceSectionIndex - sectionDeleteOffset]
+            thirdStageSections.append(thirdStageSection)
+
+            var fourthStageElements = ContiguousArray<Element>()
+            fourthStageElements.reserveCapacity(targetElements.count)
+
+            for targetElementIndex in targetElements.indices {
+                
+                untrackedSourceIndex = untrackedSourceIndex.flatMap { index in
+                    
+                    sourceElementTraces[sourceSectionIndex].suffix(from: index).firstIndex { !$0.isTracked }
+                }
+                let targetElementPath = ElementPath(element: targetElementIndex, section: targetSectionIndex)
+                let targetElement = contiguousTargetSections[targetElementPath]
+
+                guard
+                    let sourceElementPath = targetElementReferences[targetElementPath],
+                    let movedSourceSectionIndex = sectionResult.sourceTraces[sourceElementPath.section].reference
+                    else {
+                        
+                        fourthStageElements.append(targetElement)
+                        elementInserted.append(targetElementPath)
+                        continue
+                }
+                sourceElementTraces[sourceElementPath].isTracked = true
+
+                let sourceElement = contiguousSourceSections[sourceElementPath]
+                fourthStageElements.append(targetElement)
+
+                if !targetElement.isContentEqual(to: sourceElement) {
+                    
+                    elementUpdated.append(sourceElementPath)
+                }
+                if sourceElementPath.section != sourceSectionIndex || sourceElementPath.element != untrackedSourceIndex {
+                    
+                    let deleteOffset = sourceElementTraces[sourceElementPath].deleteOffset
+                    let moveSourceElementPath = ElementPath(element: sourceElementPath.element - deleteOffset, section: movedSourceSectionIndex)
+                    elementMoved.append((source: moveSourceElementPath, target: targetElementPath))
+                }
+            }
+            let fourthStageSection = Section(source: thirdStageSection, elements: fourthStageElements)
+            fourthStageSections.append(fourthStageSection)
+        }
+
+        var changesets = ContiguousArray<Changeset<C>>()
+        if !elementUpdated.isEmpty {
+            
+            changesets.append(
+                Changeset(
+                    data: C(firstStageSections),
+                    elementUpdated: elementUpdated
+                )
+            )
+        }
+        if !sectionResult.deleted.isEmpty || !elementDeleted.isEmpty {
+            
+            changesets.append(
+                Changeset(
+                    data: C(secondStageSections),
+                    sectionDeleted: sectionResult.deleted,
+                    elementDeleted: elementDeleted
+                )
+            )
+        }
+        if !sectionResult.inserted.isEmpty || !sectionResult.moved.isEmpty {
+            
+            changesets.append(
+                Changeset(
+                    data: C(thirdStageSections),
+                    sectionInserted: sectionResult.inserted,
+                    sectionMoved: sectionResult.moved
+                )
+            )
+        }
+        if !elementInserted.isEmpty || !elementMoved.isEmpty {
+            
+            changesets.append(
+                Changeset(
+                    data: C(fourthStageSections),
+                    elementInserted: elementInserted,
+                    elementMoved: elementMoved
+                )
+            )
+        }
+        if !sectionResult.updated.isEmpty {
+            
+            changesets.append(
+                Changeset(
+                    data: target,
+                    sectionUpdated: sectionResult.updated
+                )
+            )
+        }
+        if !changesets.isEmpty {
+            
+            let index = changesets.index(before: changesets.endIndex)
+            changesets[index].data = target
+        }
+        self.init(changesets)
+    }
+}
+
+
+// MARK: - MutableCollection
+
+extension MutableCollection where Element: MutableCollection, Index == Int, Element.Index == Int {
+    
+    @inlinable
+    internal subscript<O>(path: Internals.DiffableDataUIDispatcher<O>.ElementPath) -> Element.Element {
+        
+        get { return self[path.section][path.element] }
+        set { self[path.section][path.element] = newValue }
+    }
+}
+
+#endif

Sources/Internals.DiffableDataUIDispatcher.swift

@@ -0,0 +1,229 @@
+//
+//  Internals.DiffableDataUIDispatcher.swift
+//  CoreStore
+//
+//  Copyright © 2018 John Rommel Estropia
+//
+//  Permission is hereby granted, free of charge, to any person obtaining a copy
+//  of this software and associated documentation files (the "Software"), to deal
+//  in the Software without restriction, including without limitation the rights
+//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+//  copies of the Software, and to permit persons to whom the Software is
+//  furnished to do so, subject to the following conditions:
+//
+//  The above copyright notice and this permission notice shall be included in all
+//  copies or substantial portions of the Software.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+//  SOFTWARE.
+//
+
+#if canImport(UIKit) || canImport(AppKit)
+
+import CoreData
+
+#if canImport(QuartzCore)
+import QuartzCore
+
+#endif
+
+
+// MARK: - Internals
+
+extension Internals {
+
+    // MARK: Internal
+
+    // Implementation based on https://github.com/ra1028/DiffableDataSources
+    @usableFromInline
+    internal final class DiffableDataUIDispatcher<O: DynamicObject> {
+
+        // MARK: Internal
+        
+        typealias ObjectType = O
+        
+        init(dataStack: DataStack) {
+            
+            self.dataStack = dataStack
+        }
+        
+        func apply<View: AnyObject>(_ snapshot: DiffableDataSourceSnapshot, view: View?, animatingDifferences: Bool, performUpdates: @escaping (View, StagedChangeset<[Internals.DiffableDataSourceSnapshot.Section]>, @escaping ([Internals.DiffableDataSourceSnapshot.Section]) -> Void) -> Void) {
+            
+            self.dispatcher.dispatch { [weak self] in
+                
+                guard let self = self else {
+                    
+                    return
+                }
+
+                self.currentSnapshot = snapshot
+
+                let newSections = snapshot.sections
+                guard let view = view else {
+                    
+                    return self.sections = newSections
+                }
+
+                let performDiffingUpdates: () -> Void = {
+                    
+                    let changeset = StagedChangeset(source: self.sections, target: newSections)
+                    performUpdates(view, changeset) { sections in
+                        
+                        self.sections = sections
+                    }
+                }
+
+                #if canImport(QuartzCore)
+                
+                if !animatingDifferences {
+                    
+                    CATransaction.begin()
+                    CATransaction.setDisableActions(true)
+                    
+                    performDiffingUpdates()
+                    
+                    CATransaction.commit()
+                    return
+                }
+                
+                #endif
+                
+                performDiffingUpdates()
+            }
+        }
+
+        func snapshot() -> DiffableDataSourceSnapshot {
+            
+            var snapshot: DiffableDataSourceSnapshot = .init()
+            snapshot.sections = self.currentSnapshot.sections
+            return snapshot
+        }
+
+        func itemIdentifier(for indexPath: IndexPath) -> O.ObjectID? {
+            
+            guard (0 ..< self.sections.endIndex) ~= indexPath.section else {
+                
+                return nil
+            }
+            let items = self.sections[indexPath.section].elements
+            guard (0 ..< items.endIndex) ~= indexPath.item else {
+                
+                return nil
+            }
+            return items[indexPath.item].differenceIdentifier
+        }
+
+        func indexPath(for itemIdentifier: O.ObjectID) -> IndexPath? {
+            
+            let indexPathMap: [O.ObjectID: IndexPath] = self.sections.enumerated().reduce(into: [:]) { result, section in
+                
+                for (itemIndex, item) in section.element.elements.enumerated() {
+                    
+                    result[item.differenceIdentifier] = IndexPath(
+                        item: itemIndex,
+                        section: section.offset
+                    )
+                }
+            }
+            return indexPathMap[itemIdentifier]
+        }
+
+        func numberOfSections() -> Int {
+            
+            return self.sections.count
+        }
+
+        func numberOfItems(inSection section: Int) -> Int {
+            
+            return self.sections[section].elements.count
+        }
+        
+        func sectionIdentifier(inSection section: Int) -> String {
+            
+            return self.sections[section].differenceIdentifier
+        }
+
+
+        // MARK: Private
+
+        private let dispatcher: MainThreadSerialDispatcher = .init()
+        private let dataStack: DataStack
+
+        private var currentSnapshot: Internals.DiffableDataSourceSnapshot = .init()
+        private var sections: [Internals.DiffableDataSourceSnapshot.Section] = []
+        
+        
+        // MARK: - ElementPath
+        
+        @usableFromInline
+        internal struct ElementPath: Hashable {
+            
+            @usableFromInline
+            var element: Int
+            
+            @usableFromInline
+            var section: Int
+
+            @inlinable
+            init(element: Int, section: Int) {
+                
+                self.element = element
+                self.section = section
+            }
+        }
+
+
+        // MARK: - MainThreadSerialDispatcher
+
+        fileprivate final class MainThreadSerialDispatcher {
+
+            // MARK: FilePrivate
+
+            fileprivate init() {
+
+                self.executingCount.initialize(to: 0)
+            }
+
+            deinit {
+
+                self.executingCount.deinitialize(count: 1)
+                self.executingCount.deallocate()
+            }
+
+            fileprivate func dispatch(_ action: @escaping () -> Void) {
+
+                let count = OSAtomicIncrement32(self.executingCount)
+                if Thread.isMainThread && count == 1 {
+
+                    action()
+                    OSAtomicDecrement32(executingCount)
+                }
+                else {
+
+                    DispatchQueue.main.async { [weak self] in
+
+                        guard let self = self else {
+
+                            return
+                        }
+                        action()
+                        OSAtomicDecrement32(self.executingCount)
+                    }
+                }
+            }
+
+
+            // MARK: Private
+
+            private let executingCount: UnsafeMutablePointer<Int32> = .allocate(capacity: 1)
+        }
+        
+    }
+}
+
+#endif

Sources/Internals.FallbackDiffableDataUIDispatcher.swift

@@ -1,157 +0,0 @@
-//
-//  Internals.FallbackDiffableDataUIDispatcher.swift
-//  CoreStore
-//
-//  Copyright © 2018 John Rommel Estropia
-//
-//  Permission is hereby granted, free of charge, to any person obtaining a copy
-//  of this software and associated documentation files (the "Software"), to deal
-//  in the Software without restriction, including without limitation the rights
-//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-//  copies of the Software, and to permit persons to whom the Software is
-//  furnished to do so, subject to the following conditions:
-//
-//  The above copyright notice and this permission notice shall be included in all
-//  copies or substantial portions of the Software.
-//
-//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-//  SOFTWARE.
-//
-
-#if canImport(UIKit) || canImport(AppKit)
-
-import CoreData
-
-#if canImport(QuartzCore)
-import QuartzCore
-
-#endif
-
-
-// MARK: - Internals
-
-extension Internals {
-
-    // MARK: Internal
-
-//    // Implementation based on https://github.com/ra1028/DiffableDataSources
-//    internal final class FallbackDiffableDataUIDispatcher {
-//
-//        // MARK: Internal
-//
-//        internal func apply() {
-//
-//        }
-//
-//        func snapshot() -> DiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType> {
-//            var snapshot = DiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType>()
-//            snapshot.structure.sections = currentSnapshot.structure.sections
-//            return snapshot
-//        }
-//
-//        func itemIdentifier(for indexPath: IndexPath) -> ItemIdentifierType? {
-//            guard 0..<sections.endIndex ~= indexPath.section else {
-//                return nil
-//            }
-//
-//            let items = sections[indexPath.section].elements
-//
-//            guard 0..<items.endIndex ~= indexPath.item else {
-//                return nil
-//            }
-//
-//            return items[indexPath.item].differenceIdentifier
-//        }
-//
-//        func unsafeItemIdentifier(for indexPath: IndexPath, file: StaticString = #file, line: UInt = #line) -> ItemIdentifierType {
-//            guard let itemIdentifier = itemIdentifier(for: indexPath) else {
-//                universalError("Item not found at the specified index path(\(indexPath)).")
-//            }
-//
-//            return itemIdentifier
-//        }
-//
-//        func indexPath(for itemIdentifier: ItemIdentifierType) -> IndexPath? {
-//            let indexPathMap: [ItemIdentifierType: IndexPath] = sections.enumerated()
-//                .reduce(into: [:]) { result, section in
-//                    for (itemIndex, item) in section.element.elements.enumerated() {
-//                        result[item.differenceIdentifier] = IndexPath(
-//                            item: itemIndex,
-//                            section: section.offset
-//                        )
-//                    }
-//            }
-//            return indexPathMap[itemIdentifier]
-//        }
-//
-//        func numberOfSections() -> Int {
-//            return sections.count
-//        }
-//
-//        func numberOfItems(inSection section: Int) -> Int {
-//            return sections[section].elements.count
-//        }
-//
-//
-//
-//        // MARK: Private
-//
-//        private let dispatcher: MainThreadSerialDispatcher = .init()
-//
-//        private var currentSnapshot: Internals.DiffableDataSourceSnapshot = FallbackDiffableDataSourceSnapshot()
-//        private var sections: [FallbackDiffableDataSourceSnapshot.BackingStructure.Section] = []
-//
-//
-//        // MARK: - MainThreadSerialDispatcher
-//
-//        fileprivate final class MainThreadSerialDispatcher {
-//
-//            // MARK: FilePrivate
-//
-//            fileprivate init() {
-//
-//                self.executingCount.initialize(to: 0)
-//            }
-//
-//            deinit {
-//
-//                self.executingCount.deinitialize(count: 1)
-//                self.executingCount.deallocate()
-//            }
-//
-//            fileprivate func dispatch(_ action: @escaping () -> Void) {
-//
-//                let count = OSAtomicIncrement32(self.executingCount)
-//                if Thread.isMainThread && count == 1 {
-//
-//                    action()
-//                    OSAtomicDecrement32(executingCount)
-//                }
-//                else {
-//
-//                    DispatchQueue.main.async { [weak self] in
-//
-//                        guard let self = self else {
-//
-//                            return
-//                        }
-//                        action()
-//                        OSAtomicDecrement32(self.executingCount)
-//                    }
-//                }
-//            }
-//
-//
-//            // MARK: Private
-//
-//            private let executingCount: UnsafeMutablePointer<Int32> = .allocate(capacity: 1)
-//        }
-//    }
-}
-
-#endif

Sources/Internals.FetchedDiffableDataSourceSnapshotDelegate.swift

@@ -41,7 +41,12 @@ import AppKit
 
 internal protocol FetchedDiffableDataSourceSnapshotHandler: AnyObject {
 
-    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: DiffableDataSourceSnapshotProtocol)
+//    @available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *)
+//    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: NSDiffableDataSourceSnapshot<String, NSManagedObjectID>)
+
+    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: Internals.DiffableDataSourceSnapshot)
+    
+    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, sectionIndexTitleForSectionName sectionName: String?) -> String?
 }
 
 
@@ -75,14 +80,14 @@ 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 {
 
@@ -94,19 +99,19 @@ 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,
-                didChangeContentWith: snapshot as NSDiffableDataSourceSnapshot<NSString, NSManagedObjectID>
+//                didChangeContentWith: snapshot as NSDiffableDataSourceSnapshot<String, NSManagedObjectID>
-            )
+//            )
-        }
+//        }
-
+//
-        #endif
+//        #endif
         
         @objc
         dynamic func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
@@ -118,5 +123,14 @@ extension Internals {
                 )
             )
         }
+
+        @objc
+        dynamic func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, sectionIndexTitleForSectionName sectionName: String) -> String? {
+
+            return self.handler?.controller(
+                controller,
+                sectionIndexTitleForSectionName: sectionName
+            )
+        }
     }
 }

Sources/Internals.SharedNotificationObserver.swift

@@ -56,18 +56,19 @@ extension Internals {
         deinit {
 
             self.observer.map(NotificationCenter.default.removeObserver(_:))
+            self.observers.removeAllObjects()
         }
 
         internal func addObserver<U: AnyObject>(_ observer: U, closure: @escaping (T) -> Void) {
 
-            self.observers.setObject(Closure(closure), forKey: observer)
+            self.observers.setObject(Closure<T, Void>(closure), forKey: observer)
         }
 
 
         // MARK: Private
 
         private var observer: NSObjectProtocol!
-        private let observers: NSMapTable<AnyObject, Closure> = .weakToStrongObjects()
+        private let observers: NSMapTable<AnyObject, Closure<T, Void>> = .weakToStrongObjects()
 
         private func notifyObservers(_ sharedValue: T) {
 
@@ -77,31 +78,8 @@ extension Internals {
             }
             for closure in enumerator {
 
-                (closure as! Closure).invoke(with: sharedValue)
+                (closure as! Closure<T, Void>).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/Internals.swift

@@ -27,6 +27,7 @@ import Foundation
 
 // MARK: - Internals
 
+@usableFromInline
 internal enum Internals {
 
     // MARK: Associated Objects

Sources/ListMonitor.swift

@@ -1453,7 +1453,7 @@ extension ListMonitor: FetchedResultsControllerHandler {
         )
     }
     
-   internal func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, sectionIndexTitleForSectionName sectionName: String?) -> String? {
+    internal func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, sectionIndexTitleForSectionName sectionName: String?) -> String? {
     
         return self.sectionIndexTransformer(sectionName)
     }

Sources/ListSnapshot.swift

@@ -43,6 +43,24 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
     public typealias SectionID = String
     public typealias ItemID = O.ObjectID
     
+    public init(byCloning snapshot: ListSnapshot<O>, for dataStack: DataStack) {
+
+//        if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
+//
+//            self.init(
+//                diffableSnapshot: snapshot.diffableSnapshot as! NSDiffableDataSourceSnapshot<String, NSManagedObjectID>,
+//                context: dataStack.mainContext
+//            )
+//        }
+//        else {
+
+            self.init(
+                diffableSnapshot: snapshot.diffableSnapshot as! Internals.DiffableDataSourceSnapshot,
+                context: dataStack.mainContext
+            )
+//        }
+    }
+
     public subscript<S: Sequence>(indices indices: S) -> [LiveObject<O>] where S.Element == Index {
 
         let context = self.context!
@@ -252,13 +270,29 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
     
     // MARK: Internal
     
+    internal private(set) var diffableSnapshot: DiffableDataSourceSnapshotProtocol
+    
     internal init() {
 
-        self.diffableSnapshot = Internals.DiffableDataSourceSnapshot()
+//        if #available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *) {
+//
+//            self.diffableSnapshot = NSDiffableDataSourceSnapshot<String, NSManagedObjectID>()
+//        }
+//        else {
+            
+            self.diffableSnapshot = Internals.DiffableDataSourceSnapshot()
+//        }
         self.context = nil
     }
     
-    internal init(diffableSnapshot: DiffableDataSourceSnapshotProtocol, context: NSManagedObjectContext) {
+//    @available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *)
+//    internal init(diffableSnapshot: NSDiffableDataSourceSnapshot<String, NSManagedObjectID>, context: NSManagedObjectContext) {
+//
+//        self.diffableSnapshot = diffableSnapshot
+//        self.context = context
+//    }
+    
+    internal init(diffableSnapshot: Internals.DiffableDataSourceSnapshot, context: NSManagedObjectContext) {
 
         self.diffableSnapshot = diffableSnapshot
         self.context = context
@@ -270,5 +304,4 @@ public struct ListSnapshot<O: DynamicObject>: SnapshotResult, RandomAccessCollec
     private let id: UUID = .init()
     private let context: NSManagedObjectContext?
 
-    private var diffableSnapshot: DiffableDataSourceSnapshotProtocol
 }

Sources/LiveList.swift

@@ -45,29 +45,6 @@ public final class LiveList<O: DynamicObject>: Hashable {
     public typealias SectionID = SnapshotType.SectionID
     public typealias ItemID = SnapshotType.ItemID
 
-    public fileprivate(set) var snapshot: SnapshotType = .init() {
-
-        willSet {
-
-            self.willChange()
-        }
-    }
-
-    public var numberOfItems: Int {
-
-        return self.snapshot.numberOfItems
-    }
-
-    public var numberOfSections: Int {
-
-        return self.snapshot.numberOfSections
-    }
-
-    public var sectionIdentifiers: [SectionID] {
-
-        return self.snapshot.sectionIdentifiers
-    }
-
     public subscript(section sectionID: SectionID) -> [LiveObject<O>] {
 
         let context = self.context
@@ -85,6 +62,24 @@ public final class LiveList<O: DynamicObject>: Hashable {
         return self.context.liveObject(id: validID)
     }
 
+    public subscript(indexPath indexPath: IndexPath) -> LiveObject<O>? {
+        
+        let snapshot = self.snapshot
+        let sectionIdentifiers = snapshot.sectionIdentifiers
+        guard sectionIdentifiers.indices.contains(indexPath.section) else {
+            
+            return nil
+        }
+        let sectionID = sectionIdentifiers[indexPath.section]
+        let itemIdentifiers = snapshot.itemIdentifiers(inSection: sectionID)
+        guard itemIdentifiers.indices.contains(indexPath.item) else {
+            
+            return nil
+        }
+        let itemID = itemIdentifiers[indexPath.item]
+        return self.context.liveObject(id: itemID)
+    }
+
     public subscript<S: Sequence>(section sectionID: SectionID, itemIndices itemIndices: S) -> [LiveObject<O>] where S.Element == Int {
 
         let context = self.context
@@ -96,6 +91,34 @@ public final class LiveList<O: DynamicObject>: Hashable {
         }
     }
 
+    public fileprivate(set) var snapshot: SnapshotType = .init() {
+
+        willSet {
+
+            self.willChange()
+        }
+        didSet {
+            
+            self.notifyObservers(self.snapshot)
+            self.didChange()
+        }
+    }
+
+    public var numberOfItems: Int {
+
+        return self.snapshot.numberOfItems
+    }
+
+    public var numberOfSections: Int {
+
+        return self.snapshot.numberOfSections
+    }
+
+    public var sectionIdentifiers: [SectionID] {
+
+        return self.snapshot.sectionIdentifiers
+    }
+
     public var items: [LiveObject<O>] {
 
         let context = self.context
@@ -142,6 +165,26 @@ public final class LiveList<O: DynamicObject>: Hashable {
         return self.snapshot.indexOfSection(identifier)
     }
     
+    public func addObserver<T: AnyObject>(_ observer: T, _ callback: @escaping (LiveList<O>, ListSnapshot<O>) -> Void) {
+        
+        self.observers.setObject(
+            Internals.Closure(callback),
+            forKey: observer
+        )
+        
+        callback(self, self.snapshot)
+    }
+    
+    public func removeObserver<T: AnyObject>(_ observer: T) {
+        
+        self.observers.removeObject(forKey: observer)
+    }
+
+    deinit {
+
+        self.observers.removeAllObjects()
+    }
+
 
     // MARK: Equatable
 
@@ -222,12 +265,14 @@ public final class LiveList<O: DynamicObject>: Hashable {
 
     private var fetchedResultsController: Internals.CoreStoreFetchedResultsController
     private var fetchedResultsControllerDelegate: Internals.FetchedDiffableDataSourceSnapshotDelegate
+    private let sectionIndexTransformer: (_ sectionName: KeyPathString?) -> String?
     private var applyFetchClauses: (_ fetchRequest: Internals.CoreStoreFetchRequest<NSManagedObject>) -> Void
     private var observerForWillChangePersistentStore: Internals.NotificationObserver!
     private var observerForDidChangePersistentStore: Internals.NotificationObserver!
 
     private let from: From<ObjectType>
     private let sectionBy: SectionBy<ObjectType>?
+    private let observers: NSMapTable<AnyObject, Internals.Closure<(LiveList<O>, ListSnapshot<O>), Void>> = .weakToStrongObjects()
 
     private lazy var context: NSManagedObjectContext = self.fetchedResultsController.managedObjectContext
 
@@ -279,20 +324,31 @@ public final class LiveList<O: DynamicObject>: Hashable {
             self.rawObjectWillChange = nil
         }
 
+        if let sectionIndexTransformer = sectionBy?.sectionIndexTransformer {
 
-//        if let sectionIndexTransformer = sectionBy?.sectionIndexTransformer {
+            self.sectionIndexTransformer = sectionIndexTransformer
-//
+        }
-//            self.sectionIndexTransformer = sectionIndexTransformer
+        else {
-//        }
+
-//        else {
+            self.sectionIndexTransformer = { $0 }
-//
+        }
-//            self.sectionIndexTransformer = { $0 }
-//        }
         self.applyFetchClauses = applyFetchClauses
         self.fetchedResultsControllerDelegate.handler = self
 
         try! self.fetchedResultsController.performFetchFromSpecifiedStores()
     }
+
+    private func notifyObservers(_ snapshot: ListSnapshot<O>) {
+
+        guard let enumerator = self.observers.objectEnumerator() else {
+
+            return
+        }
+        for closure in enumerator {
+
+            (closure as! Internals.Closure<(LiveList<O>, ListSnapshot<O>), Void>).invoke(with: (self, snapshot))
+        }
+    }
 }
 
 
@@ -302,13 +358,27 @@ extension LiveList: FetchedDiffableDataSourceSnapshotHandler {
 
     // MARK: FetchedDiffableDataSourceSnapshotHandler
     
-    internal func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: DiffableDataSourceSnapshotProtocol) {
+//    @available(iOS 13.0, tvOS 13.0, watchOS 6.0, macOS 10.15, *)
+//    internal func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: NSDiffableDataSourceSnapshot<String, NSManagedObjectID>) {
+//
+//        self.snapshot = .init(
+//            diffableSnapshot: snapshot,
+//            context: controller.managedObjectContext
+//        )
+//    }
+
+    internal func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: Internals.DiffableDataSourceSnapshot) {
 
         self.snapshot = .init(
             diffableSnapshot: snapshot,
             context: controller.managedObjectContext
         )
     }
+    
+    internal func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, sectionIndexTitleForSectionName sectionName: String?) -> String? {
+    
+        return self.sectionIndexTransformer(sectionName)
+    }
 }