Interactive Reordering

CHANGELOG.md

@@ -17,6 +17,8 @@ The changelog for `IGListKit`. Also see the [releases](https://github.com/instag
 
 - Added experiment to make  `-[IGListAdapter visibleSectionControllers:]` a bit faster. [Maxime Ollivier](https://github.com/maxoll) (tbd)
 
+- Added support for UICollectionView's interactive reordering in iOS 9+.  Updates include `-[IGListSectionController canMoveItemAtIndex:]` to enable the behavior, `-[IGListSectionController moveObjectFromIndex:toIndex:]` called when items within a section controller were moved through reordering, `-[IGListAdapterDataSource listAdapter:moveObject:from:to]` called when section controllers themselves were reordered (only possible when all section controllers contain exactly 1 object), and `-[IGListUpdatingDelegate moveSectionInCollectionView:fromIndex:toIndex]` to enable custom updaters to conform to the reordering behavior. The update also includes two new examples `ReorderableSectionController` and `ReorderableStackedViewController` to demonstrate how to enable interactive reordering in your client app. [Jared Verdi](https://github.com/jverdi) [(#976)](https://github.com/Instagram/IGListKit/pull/976)
+
 ### Fixes
 
 - Duplicate objects for initial data source setup filtered out. [Mikhail Vashlyaev](https://github.com/yemodin) [(#993](https://github.com/Instagram/IGListKit/pull/993)

Examples/Examples-iOS/IGListKitExamples.xcodeproj/project.pbxproj

@@ -8,6 +8,10 @@
 
 /* Begin PBXBuildFile section */
 		07C17786BCC6ABD68C8BFA69 /* Pods_IGListKitTodayExample.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 49DEF56A3C9C414B461D113F /* Pods_IGListKitTodayExample.framework */; };
+		13BD88281FA3C630001BA5F5 /* PrefixedLabelSectionController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 13BD88271FA3C630001BA5F5 /* PrefixedLabelSectionController.swift */; };
+		13DF01681F9D9CBD0092A320 /* ReorderableSectionController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 13DF01671F9D9CBD0092A320 /* ReorderableSectionController.swift */; };
+		13DF016A1F9D9F600092A320 /* ReorderableViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 13DF01691F9D9F600092A320 /* ReorderableViewController.swift */; };
+		13DF01811FA391740092A320 /* ReorderableStackedViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 13DF01801FA391740092A320 /* ReorderableStackedViewController.swift */; };
 		26271C8E1DAE9D3F0073E116 /* SingleSectionViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26271C8D1DAE9D3F0073E116 /* SingleSectionViewController.swift */; };
 		26271C921DAE9EFC0073E116 /* NibCell.xib in Resources */ = {isa = PBXBuildFile; fileRef = 26271C911DAE9EFC0073E116 /* NibCell.xib */; };
 		26271C941DAE9F050073E116 /* NibCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = 26271C931DAE9F050073E116 /* NibCell.swift */; };
@@ -140,6 +144,10 @@
 /* End PBXCopyFilesBuildPhase section */
 
 /* Begin PBXFileReference section */
+		13BD88271FA3C630001BA5F5 /* PrefixedLabelSectionController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PrefixedLabelSectionController.swift; sourceTree = "<group>"; };
+		13DF01671F9D9CBD0092A320 /* ReorderableSectionController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ReorderableSectionController.swift; sourceTree = "<group>"; };
+		13DF01691F9D9F600092A320 /* ReorderableViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ReorderableViewController.swift; sourceTree = "<group>"; };
+		13DF01801FA391740092A320 /* ReorderableStackedViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ReorderableStackedViewController.swift; sourceTree = "<group>"; };
 		26271C8D1DAE9D3F0073E116 /* SingleSectionViewController.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = SingleSectionViewController.swift; sourceTree = "<group>"; };
 		26271C911DAE9EFC0073E116 /* NibCell.xib */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = file.xib; path = NibCell.xib; sourceTree = "<group>"; };
 		26271C931DAE9F050073E116 /* NibCell.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = NibCell.swift; sourceTree = "<group>"; };
@@ -335,7 +343,9 @@
 				292658631E74A2550041B56D /* MonthSectionController.swift */,
 				295D8A981E92EC96001F7C06 /* PostSectionController.h */,
 				295D8A991E92EC96001F7C06 /* PostSectionController.m */,
+				13BD88271FA3C630001BA5F5 /* PrefixedLabelSectionController.swift */,
 				2942FF891D9F39E00015D24B /* RemoveSectionController.swift */,
+				13DF01671F9D9CBD0092A320 /* ReorderableSectionController.swift */,
 				2942FF8A1D9F39E00015D24B /* SearchSectionController.swift */,
 				296DD7541DD2150600206780 /* SelfSizingSectionController.swift */,
 				821BC4B91DB8B61200172ED0 /* StoryboardLabelSectionController.swift */,
@@ -401,6 +411,8 @@
 				2991F9231D7BB89F00B0C58F /* NestedAdapterViewController.swift */,
 				56C05B671E49B2120026DB39 /* ObjcDemoViewController.h */,
 				56C05B681E49B2120026DB39 /* ObjcDemoViewController.m */,
+				13DF01801FA391740092A320 /* ReorderableStackedViewController.swift */,
+				13DF01691F9D9F600092A320 /* ReorderableViewController.swift */,
 				299B53FF1D6BD6630074A202 /* SearchViewController.swift */,
 				296DD7521DD2147500206780 /* SelfSizingCellsViewController.swift */,
 				82D91B681DBA0EF300E62758 /* SingleSectionStoryboardViewController.swift */,
@@ -861,6 +873,7 @@
 				82D91B691DBA0EF300E62758 /* SingleSectionStoryboardViewController.swift in Sources */,
 				29D2E4AF1DD69C0E00CD255D /* DisplayViewController.swift in Sources */,
 				2942FF911D9F39E00015D24B /* LabelSectionController.swift in Sources */,
+				13BD88281FA3C630001BA5F5 /* PrefixedLabelSectionController.swift in Sources */,
 				295D8A9D1E92ECDE001F7C06 /* Post.m in Sources */,
 				29F7E2AD1E92843A00197586 /* IncrementAnnouncer.swift in Sources */,
 				2981BA391DB874BB00A987F9 /* WorkingRangeViewController.swift in Sources */,
@@ -870,6 +883,7 @@
 				2991F9191D7BADC900B0C58F /* CenterLabelCell.swift in Sources */,
 				295D8A9A1E92EC96001F7C06 /* PostSectionController.m in Sources */,
 				29628F141D91905A0026B15A /* DetailLabelCell.swift in Sources */,
+				13DF01681F9D9CBD0092A320 /* ReorderableSectionController.swift in Sources */,
 				56C05B751E49B33C0026DB39 /* InteractiveCell.m in Sources */,
 				2991F9301D7BC0E400B0C58F /* EmptyViewController.swift in Sources */,
 				29F7E2AF1E92858500197586 /* ListeningSectionController.swift in Sources */,
@@ -881,10 +895,12 @@
 				2942FF941D9F39E00015D24B /* UserSectionController.swift in Sources */,
 				29459C001DBE48E200F05375 /* DiffTableViewController.swift in Sources */,
 				2991F92C1D7BBE5400B0C58F /* RemoveCell.swift in Sources */,
+				13DF01811FA391740092A320 /* ReorderableStackedViewController.swift in Sources */,
 				2942FF8D1D9F39E00015D24B /* EmbeddedSectionController.swift in Sources */,
 				29C6297B1DCFD857004A5BB1 /* SupplementaryViewController.swift in Sources */,
 				296DD7551DD2150600206780 /* SelfSizingSectionController.swift in Sources */,
 				2991F9281D7BB9EC00B0C58F /* EmbeddedCollectionViewCell.swift in Sources */,
+				13DF016A1F9D9F600092A320 /* ReorderableViewController.swift in Sources */,
 				2942FF8F1D9F39E00015D24B /* GridSectionController.swift in Sources */,
 				821BC4B81DB8B48300172ED0 /* StoryboardCell.swift in Sources */,
 				56C05B781E49B3A50026DB39 /* PhotoCell.m in Sources */,

Examples/Examples-iOS/IGListKitExamples/SectionControllers/GridSectionController.swift

@@ -20,11 +20,22 @@ final class GridItem: NSObject {
     let color: UIColor
     let itemCount: Int
 
+    var items: [String] = []
+
     init(color: UIColor, itemCount: Int) {
         self.color = color
         self.itemCount = itemCount
+
+        super.init()
+
+        self.items = computeItems()
     }
 
+    private func computeItems() -> [String] {
+        return [Int](1...itemCount).map {
+            String(describing: $0)
+        }
+    }
 }
 
 extension GridItem: ListDiffable {
@@ -42,8 +53,10 @@ extension GridItem: ListDiffable {
 final class GridSectionController: ListSectionController {
 
     private var object: GridItem?
+    private let isReorderable: Bool
 
-    override init() {
+    required init(isReorderable: Bool = false) {
+        self.isReorderable = isReorderable
         super.init()
         self.minimumInteritemSpacing = 1
         self.minimumLineSpacing = 1
@@ -63,7 +76,7 @@ final class GridSectionController: ListSectionController {
         guard let cell = collectionContext?.dequeueReusableCell(of: CenterLabelCell.self, for: self, at: index) as? CenterLabelCell else {
             fatalError()
         }
-        cell.text = "\(index + 1)"
+        cell.text = object?.items[index] ?? "undefined"
         cell.backgroundColor = object?.color
         return cell
     }
@@ -72,4 +85,13 @@ final class GridSectionController: ListSectionController {
         self.object = object as? GridItem
     }
 
+    override func canMoveItem(at index: Int) -> Bool {
+        return isReorderable
+    }
+
+    override func moveObject(from sourceIndex: Int, to destinationIndex: Int) {
+        guard let object = object else { return }
+        let item = object.items.remove(at: sourceIndex)
+        object.items.insert(item, at: destinationIndex)
+    }
 }

Examples/Examples-iOS/IGListKitExamples/SectionControllers/PrefixedLabelSectionController.swift

@@ -0,0 +1,101 @@
+/**
+ Copyright (c) 2016-present, Facebook, Inc. All rights reserved.
+
+ The examples provided by Facebook are for non-commercial testing and evaluation
+ purposes only. Facebook reserves all rights not expressly granted.
+
+ 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
+ FACEBOOK 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 UIKit
+import IGListKit
+
+final class PrefixedLabelSectionController: ListSectionController, ListSupplementaryViewSource {
+
+    private var object: LabelsItem?
+
+    private let prefix: String
+    private let group: Int
+
+    required init(prefix: String, group: Int) {
+        self.prefix = prefix
+        self.group = group
+        super.init()
+        self.minimumInteritemSpacing = 1
+        self.minimumLineSpacing = 1
+        self.supplementaryViewSource = self
+    }
+
+    override func numberOfItems() -> Int {
+        guard let object = object else { return 0 }
+        return group == 1 ? object.labels1.count : object.labels2.count
+    }
+
+    override func sizeForItem(at index: Int) -> CGSize {
+        return CGSize(width: collectionContext!.containerSize.width, height: 55)
+    }
+
+    override func cellForItem(at index: Int) -> UICollectionViewCell {
+        guard let cell = collectionContext?.dequeueReusableCell(of: LabelCell.self, for: self, at: index) as? LabelCell else {
+            fatalError()
+        }
+        if let object = object {
+            if group == 1 {
+                cell.text = "\(prefix) \(object.labels1[index])"
+            } else {
+                cell.text = "\(prefix) \(object.labels2[index])"
+            }
+        } else {
+            cell.text = "\(prefix) [X]"
+        }
+        cell.backgroundColor = object?.color
+        return cell
+    }
+
+    override func didUpdate(to object: Any) {
+        self.object = object as? LabelsItem
+    }
+
+    override func canMoveItem(at index: Int) -> Bool {
+        return true
+    }
+
+    override func moveObject(from sourceIndex: Int, to destinationIndex: Int) {
+        guard let object = object else { return }
+        if group == 1 {
+            let item = object.labels1.remove(at: sourceIndex)
+            object.labels1.insert(item, at: destinationIndex)
+        } else {
+            let item = object.labels2.remove(at: sourceIndex)
+            object.labels2.insert(item, at: destinationIndex)
+        }
+    }
+
+    // MARK: ListSupplementaryViewSource
+
+    func supportedElementKinds() -> [String] {
+        return [UICollectionElementKindSectionHeader]
+    }
+
+    func viewForSupplementaryElement(ofKind elementKind: String, at index: Int) -> UICollectionReusableView {
+        guard let view = collectionContext?.dequeueReusableSupplementaryView(ofKind: UICollectionElementKindSectionHeader,
+                                                                             for: self,
+                                                                             nibName: "UserHeaderView",
+                                                                             bundle: nil,
+                                                                             at: index) as? UserHeaderView else {
+                                                                                fatalError()
+        }
+        view.name = "Sections of Letters & Numbers"
+        view.handle = ""
+        return view
+    }
+
+    func sizeForSupplementaryView(ofKind elementKind: String, at index: Int) -> CGSize {
+        return CGSize(width: collectionContext!.containerSize.width, height: 40)
+    }
+}

Examples/Examples-iOS/IGListKitExamples/SectionControllers/ReorderableSectionController.swift

@@ -0,0 +1,41 @@
+/**
+ Copyright (c) 2016-present, Facebook, Inc. All rights reserved.
+
+ The examples provided by Facebook are for non-commercial testing and evaluation
+ purposes only. Facebook reserves all rights not expressly granted.
+
+ 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
+ FACEBOOK 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 UIKit
+import IGListKit
+
+final class ReorderableSectionController: ListSectionController {
+
+    private var object: String?
+
+    override func sizeForItem(at index: Int) -> CGSize {
+        return CGSize(width: collectionContext!.containerSize.width, height: 55)
+    }
+
+    override func cellForItem(at index: Int) -> UICollectionViewCell {
+        guard let cell = collectionContext?.dequeueReusableCell(of: LabelCell.self, for: self, at: index) as? LabelCell else {
+            fatalError()
+        }
+        cell.text = object
+        return cell
+    }
+
+    override func didUpdate(to object: Any) {
+        self.object = String(describing: object)
+    }
+
+    override func canMoveItem(at index: Int) -> Bool {
+        return true
+    }
+}

Examples/Examples-iOS/IGListKitExamples/SectionControllers/UserSectionController.swift

@@ -18,6 +18,12 @@ import IGListKit
 final class UserSectionController: ListSectionController {
 
     private var user: User?
+    private let isReorderable: Bool
+
+    required init(isReorderable: Bool = false) {
+        self.isReorderable = isReorderable
+        super.init()
+    }
 
     override func sizeForItem(at index: Int) -> CGSize {
         return CGSize(width: collectionContext!.containerSize.width, height: 55)
@@ -36,4 +42,7 @@ final class UserSectionController: ListSectionController {
         self.user = object as? User
     }
 
+    override func canMoveItem(at index: Int) -> Bool {
+        return isReorderable
+    }
 }

Examples/Examples-iOS/IGListKitExamples/ViewControllers/DemosViewController.swift

@@ -58,7 +58,11 @@ final class DemosViewController: UIViewController, ListAdapterDataSource {
         DemoItem(name: "Calendar (auto diffing)",
                  controllerClass: CalendarViewController.self),
         DemoItem(name: "Dependency Injection",
-                 controllerClass: AnnouncingDepsViewController.self)
+                 controllerClass: AnnouncingDepsViewController.self),
+        DemoItem(name: "Reorder Cells",
+                 controllerClass: ReorderableViewController.self),
+        DemoItem(name: "Reorder Stacked Section Controllers",
+                 controllerClass: ReorderableStackedViewController.self)
     ]
 
     override func viewDidLoad() {

Examples/Examples-iOS/IGListKitExamples/ViewControllers/MixedDataViewController.swift

@@ -15,14 +15,14 @@
 import UIKit
 import IGListKit
 
-final class MixedDataViewController: UIViewController, ListAdapterDataSource {
+final class MixedDataViewController: UIViewController, ListAdapterDataSource, ListAdapterMoveDelegate {
 
     lazy var adapter: ListAdapter = {
         return ListAdapter(updater: ListAdapterUpdater(), viewController: self)
     }()
     let collectionView = UICollectionView(frame: .zero, collectionViewLayout: UICollectionViewFlowLayout())
 
-    let data: [Any] = [
+    var data: [Any] = [
         "Maecenas faucibus mollis interdum. Duis mollis, est non commodo luctus, nisi erat porttitor ligula, eget lacinia odio sem nec elit.",
         GridItem(color: UIColor(red: 237/255.0, green: 73/255.0, blue: 86/255.0, alpha: 1), itemCount: 6),
         User(pk: 2, name: "Ryan Olson", handle: "ryanolsonk"),
@@ -54,9 +54,38 @@ final class MixedDataViewController: UIViewController, ListAdapterDataSource {
         control.addTarget(self, action: #selector(MixedDataViewController.onControl(_:)), for: .valueChanged)
         navigationItem.titleView = control
 
+        if #available(iOS 9.0, *) {
+            let longPressGesture = UILongPressGestureRecognizer(target: self, action: #selector(MixedDataViewController.handleLongGesture(gesture:)))
+            collectionView.addGestureRecognizer(longPressGesture)
+        }
+
         view.addSubview(collectionView)
         adapter.collectionView = collectionView
         adapter.dataSource = self
+        if #available(iOS 9.0, *) {
+            adapter.moveDelegate = self
+        }
+    }
+
+    @available(iOS 9.0, *)
+    @objc func handleLongGesture(gesture: UILongPressGestureRecognizer) {
+        switch gesture.state {
+        case .began:
+            let touchLocation = gesture.location(in: self.collectionView)
+            guard let selectedIndexPath = collectionView.indexPathForItem(at: touchLocation) else {
+                break
+            }
+            collectionView.beginInteractiveMovementForItem(at: selectedIndexPath)
+        case .changed:
+            if let view = gesture.view {
+                let position = gesture.location(in: view)
+                collectionView.updateInteractiveMovementTargetPosition(position)
+            }
+        case .ended:
+            collectionView.endInteractiveMovement()
+        default:
+            collectionView.cancelInteractiveMovement()
+        }
     }
 
     override func viewDidLayoutSubviews() {
@@ -82,10 +111,16 @@ final class MixedDataViewController: UIViewController, ListAdapterDataSource {
     func listAdapter(_ listAdapter: ListAdapter, sectionControllerFor object: Any) -> ListSectionController {
         switch object {
         case is String:   return ExpandableSectionController()
-        case is GridItem: return GridSectionController()
-        default:          return UserSectionController()
+        case is GridItem: return GridSectionController(isReorderable: true)
+        default:          return UserSectionController(isReorderable: true)
         }
     }
 
     func emptyView(for listAdapter: ListAdapter) -> UIView? { return nil }
+
+    // MARK: - ListAdapterMoveDelegate
+
+    func listAdapter(_ listAdapter: ListAdapter, move object: Any, from previousObjects: [Any], to objects: [Any]) {
+        data = objects
+    }
 }