expose new delegation APIs and handle cell deletion

Example/DeletableListViewController.swift

@@ -0,0 +1,167 @@
+//
+// Copyright (c) 2016 Adam Shin
+//
+// 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 UIKit
+import SwiftReorder
+
+class DeletableViewController: UIViewController {
+
+    var items = (1...10).map { "Item \($0)" }
+    private var tableView: UITableView!
+    private var deleteButton: UIView?
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+
+        title = "Deletable"
+
+        tableView = UITableView(frame: view.frame, style: .grouped)
+        tableView.dataSource = self
+        view.addSubview(tableView)
+        view.backgroundColor = .white
+
+        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
+        tableView.allowsSelection = false
+        tableView.reorder.delegate = self
+    }
+
+    private func showDeleteButton() {
+        let button = UIView()
+        button.translatesAutoresizingMaskIntoConstraints = false
+        view.addSubview(button)
+
+        let bottomAnchor: NSLayoutYAxisAnchor
+        if #available(iOS 11, *) {
+            bottomAnchor = view.safeAreaLayoutGuide.bottomAnchor
+        } else {
+            bottomAnchor = view.bottomAnchor
+        }
+        NSLayoutConstraint.activate([
+            button.leadingAnchor.constraint(equalTo: view.leadingAnchor),
+            button.trailingAnchor.constraint(equalTo: view.trailingAnchor),
+            button.heightAnchor.constraint(equalToConstant: 50),
+            button.bottomAnchor.constraint(equalTo: bottomAnchor)
+            ])
+
+        let label = UILabel()
+        label.text = "💣"
+        label.textAlignment = .center
+        label.translatesAutoresizingMaskIntoConstraints = false
+        button.addSubview(label)
+
+        NSLayoutConstraint.activate([
+            label.widthAnchor.constraint(equalToConstant: 50),
+            label.heightAnchor.constraint(equalToConstant: 50),
+            label.centerXAnchor.constraint(equalTo: button.centerXAnchor),
+            label.centerYAnchor.constraint(equalTo: button.centerYAnchor)
+            ])
+
+        deleteButton = button
+
+        if let snapshot = tableView.reorder.snapshotView {
+            snapshot.superview?.bringSubviewToFront(snapshot)
+        }
+    }
+
+    private func removeDeleteButton() {
+        deleteButton?.removeFromSuperview()
+    }
+
+    private func handleCellMove(with gestureRecognizer: UIGestureRecognizer) {
+        guard let deletionRatio = getDeletionRatio(from: gestureRecognizer),
+            let snapshot = tableView.reorder.snapshotView else {
+                return
+        }
+
+        if deletionRatio > 0 {
+            snapshot.alpha = 1 - deletionRatio
+        } else {
+            snapshot.alpha = 1
+        }
+    }
+
+    private func getDeletionRatio(from gestureRecognizer: UIGestureRecognizer) -> CGFloat? {
+        guard let deleteButton = deleteButton else {
+            return nil
+        }
+        let position = gestureRecognizer.location(in: deleteButton).y
+        let targetPosition = deleteButton.frame.height / 2
+        let targetSize = deleteButton.frame.height
+        let deletionRatio = max(1 - abs(position - targetPosition) / targetSize, 0)
+        return deletionRatio
+    }
+}
+
+extension DeletableViewController: UITableViewDataSource {
+
+    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
+        return items.count
+    }
+
+    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
+        if let spacer = tableView.reorder.spacerCell(for: indexPath) {
+            return spacer
+        }
+
+        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
+        cell.textLabel?.text = items[indexPath.row]
+
+        return cell
+    }
+
+}
+
+extension DeletableViewController: TableViewReorderDelegate {
+
+    func tableView(_ tableView: UITableView, reorderRowAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {
+        let item = items[sourceIndexPath.row]
+        items.remove(at: sourceIndexPath.row)
+        items.insert(item, at: destinationIndexPath.row)
+    }
+
+    func tableViewDidBeginReordering(_ tableView: UITableView, at indexPath: IndexPath) {
+        showDeleteButton()
+    }
+
+    func tableViewShouldRemoveCell(_ tableView: UITableView, from initialSourceIndexPath: IndexPath, to finalDestinationIndexPath: IndexPath, with gestureRecognizer: UIGestureRecognizer) -> Bool {
+        guard let deletionRatio = getDeletionRatio(from: gestureRecognizer) else {
+            return false
+        }
+        if deletionRatio > 0.5 {
+            return true
+        }
+        return false
+    }
+
+    func tableViewDidMoveCell(_ tableView: UITableView, with gestureRecognizer: UIGestureRecognizer) {
+        handleCellMove(with: gestureRecognizer)
+    }
+
+    func tableViewDidFinishReordering(_ tableView: UITableView, from initialSourceIndexPath: IndexPath, to finalDestinationIndexPath: IndexPath) {
+        removeDeleteButton()
+    }
+
+    func tableViewDidFinishReorderingWithDeletion(_ tableView: UITableView, from initialSourceIndexPath: IndexPath, last lastIndexPath: IndexPath) {
+        items.remove(at: finalDestinationIndexPath.row)
+        removeDeleteButton()
+    }
+}

Example/RootViewController.swift

@@ -31,6 +31,7 @@ class RootViewController: UITableViewController {
         case nonMovable
         case effects
         case customCells
+        case deletable
 
         case count
     }
@@ -75,6 +76,8 @@ extension RootViewController {
             cell.textLabel?.text = "Effects"
         case .customCells:
             cell.textLabel?.text = "Custom Cells"
+        case .deletable:
+            cell.textLabel?.text = "Deletable Cells"
         case .count:
             break
         }
@@ -97,6 +100,8 @@ extension RootViewController {
             navigationController?.pushViewController(EffectsViewController(), animated: true)
         case .customCells:
             navigationController?.pushViewController(CustomCellsViewController(), animated: true)
+        case .deletable:
+            navigationController?.pushViewController(DeletableViewController(), animated: true)
         case .count:
             break
         }

Source/ReorderController+GestureRecognizer.swift

@@ -34,10 +34,10 @@ extension ReorderController {
             beginReorder(touchPosition: touchPosition)
 
         case .changed:
-            updateReorder(touchPosition: touchPosition)
+            updateReorder(touchPosition: touchPosition, gestureRecognizer: gestureRecognizer)
 
         case .ended, .cancelled, .failed, .possible:
-            endReorder()
+            endReorder(gestureRecognizer: gestureRecognizer)
         @unknown default: break
         }
     }

Source/ReorderController.swift

@@ -73,13 +73,36 @@ public protocol TableViewReorderDelegate: class {
     func tableViewDidBeginReordering(_ tableView: UITableView, at indexPath: IndexPath)
 
     /**
-     Tells the delegate that the user has finished reordering.
+     Tells the delegate that the user has finished reordering and that the row was moved.
      - Parameter tableView: The table view providing this information.
      - Parameter initialSourceIndexPath: The initial index path of the selected row, before reordering began.
      - Parameter finalDestinationIndexPath: The final index path of the selected row.
      */
     func tableViewDidFinishReordering(_ tableView: UITableView, from initialSourceIndexPath: IndexPath, to finalDestinationIndexPath: IndexPath)
 
+    /**
+     Tells the delegate that the user has finished reordering and that the row was deleted.
+     - Parameter tableView: The table view providing this information.
+     - Parameter initialSourceIndexPath: The initial index path of the selected row, before reordering began.
+     - Parameter lastIndexPath: The last index path of cell before it got deleted
+     */
+    func tableViewDidFinishReorderingWithDeletion(_ tableView: UITableView, from initialSourceIndexPath: IndexPath, last lastIndexPath: IndexPath)
+
+    /**
+     Tells the delegate that the user has moved the cell
+     - Parameter tableView: The table view providing this information.
+     - Parameter gestureRecognizer: The user gesture that moved the cell.
+     */
+    func tableViewDidMoveCell(_ tableView: UITableView, with gestureRecognizer: UIGestureRecognizer)
+
+    /**
+     Asks the delegate whether the cell should be deleted
+     - Parameter tableView: The table view providing this information.
+     - Parameter initialSourceIndexPath: The initial index path of the selected row, before reordering began.
+     - Parameter finalDestinationIndexPath: The current index path of the selected row.
+     - Parameter gestureRecognizer: The user gesture that moved the cell and has now ended.
+     */
+    func tableViewShouldRemoveCell(_ tableView: UITableView, from initialSourceIndexPath: IndexPath, to finalDestinationIndexPath: IndexPath, with gestureRecognizer: UIGestureRecognizer) -> Bool
 }
 
 public extension TableViewReorderDelegate {
@@ -98,6 +121,15 @@ public extension TableViewReorderDelegate {
     func tableViewDidFinishReordering(_ tableView: UITableView, from initialSourceIndexPath: IndexPath, to finalDestinationIndexPath:IndexPath) {
     }
 
+    func tableViewDidMoveCell(_ tableView: UITableView, with gestureRecognizer: UIGestureRecognizer) {
+    }
+
+    func tableViewShouldRemoveCell(_ tableView: UITableView, from initialSourceIndexPath: IndexPath, to finalDestinationIndexPath: IndexPath, with gestureRecognizer: UIGestureRecognizer) -> Bool {
+        return false
+    }
+
+    func tableViewDidFinishReorderingWithDeletion(_ tableView: UITableView, from initialSourceIndexPath: IndexPath, last lastIndexPath: IndexPath) {
+    }
 }
 
 // MARK: - ReorderController
@@ -156,6 +188,9 @@ public class ReorderController: NSObject {
     /// Whether or not autoscrolling is enabled
     public var autoScrollEnabled = true
 
+    /// The view used to represent the cell being reordered
+    public internal(set) var snapshotView: UIView? = nil
+
     /**
      Returns a `UITableViewCell` if the table view should display a spacer cell at the given index path.
 
@@ -198,7 +233,6 @@ public class ReorderController: NSObject {
     weak var tableView: UITableView?
 
     var reorderState: ReorderState = .ready(snapshotRow: nil)
-    var snapshotView: UIView? = nil
 
     var autoScrollDisplayLink: CADisplayLink?
     var lastAutoScrollTimeStamp: CFTimeInterval?
@@ -255,18 +289,20 @@ public class ReorderController: NSObject {
         delegate.tableViewDidBeginReordering(tableView, at: sourceRow)
     }
 
-    func updateReorder(touchPosition: CGPoint) {
-        guard case .reordering(let context) = reorderState else { return }
+    func updateReorder(touchPosition: CGPoint, gestureRecognizer: UIGestureRecognizer) {
+        guard case .reordering(let context) = reorderState, let tableView = tableView else { return }
 
         var newContext = context
         newContext.touchPosition = touchPosition
         reorderState = .reordering(context: newContext)
 
         updateSnapshotViewPosition()
         updateDestinationRow()
+
+        delegate?.tableViewDidMoveCell(tableView, with: gestureRecognizer)
     }
 
-    func endReorder() {
+    func endReorder(gestureRecognizer: UIGestureRecognizer) {
         guard case .reordering(let context) = reorderState,
             let tableView = tableView,
             let superview = tableView.superview
@@ -284,16 +320,40 @@ public class ReorderController: NSObject {
             snapshotView?.center.y += 0.1
         }
 
+        guard delegate?.tableViewShouldRemoveCell(
+            tableView,
+            from: context.sourceRow,
+            to: context.destinationRow,
+            with: gestureRecognizer
+            ) != true else {
+                removeSnapshotView()
+                clearAutoScrollDisplayLink()
+                reorderState = .ready(snapshotRow: nil)
+
+                UIView.performWithoutAnimation {
+                    delegate?.tableViewDidFinishReorderingWithDeletion(tableView, from: context.sourceRow, last: context.destinationRow)
+                    tableView.deleteRows(at: [context.destinationRow], with: .none)
+                }
+                return
+        }
+
         UIView.animate(withDuration: animationDuration,
             animations: {
                 self.snapshotView?.center = CGPoint(x: cellRect.midX, y: cellRect.midY)
             },
             completion: { _ in
                 if case let .ready(snapshotRow) = self.reorderState, let row = snapshotRow {
                     self.reorderState = .ready(snapshotRow: nil)
-                    UIView.performWithoutAnimation {
-                        tableView.reloadRows(at: [row], with: .none)
+
+                    if let rowCount = tableView.dataSource?.tableView(tableView, numberOfRowsInSection: row.section),
+                        rowCount > row.row {
+                        // else the row has been removed during the animation and calling
+                        // the following would crash
+                        UIView.performWithoutAnimation {
+                            tableView.reloadRows(at: [row], with: .none)
+                        }
                     }
+
                     self.removeSnapshotView()
                 }
             }

SwiftReorder.xcodeproj/project.pbxproj

@@ -7,6 +7,7 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		63B93AE2229E247E00D62F10 /* DeletableListViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 63B93AE1229E247E00D62F10 /* DeletableListViewController.swift */; };
 		66FC50F11D5EE49D00CFCCCE /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 66FC50E81D5EE49D00CFCCCE /* AppDelegate.swift */; };
 		66FC50F21D5EE49D00CFCCCE /* BasicViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 66FC50E91D5EE49D00CFCCCE /* BasicViewController.swift */; };
 		66FC50F41D5EE49D00CFCCCE /* EffectsViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 66FC50EB1D5EE49D00CFCCCE /* EffectsViewController.swift */; };
@@ -51,6 +52,7 @@
 /* End PBXCopyFilesBuildPhase section */
 
 /* Begin PBXFileReference section */
+		63B93AE1229E247E00D62F10 /* DeletableListViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DeletableListViewController.swift; sourceTree = "<group>"; };
 		660256931CE6A5170029CB5F /* SwiftReorderExample.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = SwiftReorderExample.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		66DF25101D8080A000C19289 /* ReorderController+AutoScroll.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; name = "ReorderController+AutoScroll.swift"; path = "Source/ReorderController+AutoScroll.swift"; sourceTree = "<group>"; };
 		66DF25111D8080A000C19289 /* ReorderController+DestinationRow.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; name = "ReorderController+DestinationRow.swift"; path = "Source/ReorderController+DestinationRow.swift"; sourceTree = "<group>"; };
@@ -122,6 +124,7 @@
 				66FC50EB1D5EE49D00CFCCCE /* EffectsViewController.swift */,
 				AB6E455B21A82AAD00D47CFC /* CustomCellsViewController.swift */,
 				66FC50ED1D5EE49D00CFCCCE /* Info.plist */,
+				63B93AE1229E247E00D62F10 /* DeletableListViewController.swift */,
 			);
 			path = Example;
 			sourceTree = "<group>";
@@ -262,6 +265,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				63B93AE2229E247E00D62F10 /* DeletableListViewController.swift in Sources */,
 				66FC50F91D5EE49D00CFCCCE /* RootViewController.swift in Sources */,
 				AB6E455C21A82AAD00D47CFC /* CustomCellsViewController.swift in Sources */,
 				66FC50F81D5EE49D00CFCCCE /* NonMovableViewController.swift in Sources */,