Interactive Reordering

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

@@ -53,8 +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
@@ -83,6 +85,10 @@ 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)

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/MixedDataViewController.swift

@@ -108,21 +108,13 @@ 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 }
 
-    func listAdapter(_ listAdapter: ListAdapter, canMoveObjectInSection sectionIndex: Int, at index: Int) -> Bool {
-        if data[sectionIndex] as? String != nil {
-            // for testing purposes, allow moving grid items and users, but not simple strings
-            return false
-        }
-        return true
-    }
-
     func listAdapter(_ listAdapter: ListAdapter, moveSectionAt sourceIndex: Int, to destinationIndex: Int) {
         let obj = data.remove(at: sourceIndex)
         data.insert(obj, at: destinationIndex)

Source/IGListAdapterDataSource.h

@@ -63,15 +63,6 @@ NS_SWIFT_NAME(ListAdapterDataSource)
 
 @optional
 
-/**
- Asks the datasource whether a list object should be movable as the result of interactive reordering.
-
- @param listAdapter The list adapter sending this information.
- @param sectionIndex The index of the section proposed to be moved.
- @param index The index of the object proposed to be moved.
- */
-- (BOOL)listAdapter:(IGListAdapter *)listAdapter canMoveObjectInSection:(NSInteger)sectionIndex atIndex:(NSInteger)index;
-
 /**
  Notifies the datasource that a list object should move as the result of interactive reordering.
 

Source/Internal/IGListAdapter+UICollectionView.m

@@ -59,18 +59,9 @@ - (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView
 }
 
 - (BOOL)collectionView:(UICollectionView *)collectionView canMoveItemAtIndexPath:(NSIndexPath *)indexPath {
-    id <IGListAdapterDataSource> dataSource = self.dataSource;
-    IGAssert(dataSource != nil, @"Found a nil dataSource when requesting canMoveItemAtIndexPath for interactive reordering");
-
     const NSInteger sectionIndex = indexPath.section;
     const NSInteger itemIndex = indexPath.item;
 
-    // for ease of implementation, first we check with the listAdapter
-    if ([dataSource respondsToSelector:@selector(listAdapter:canMoveObjectInSection:atIndex:)]) {
-        return [dataSource listAdapter:self canMoveObjectInSection:sectionIndex atIndex:itemIndex];
-    }
-
-    // then we fall back to the sectionController method
     IGListSectionController *sectionController = [self sectionControllerForSection:sectionIndex];
     return [sectionController canMoveItemAtIndex:itemIndex];
 }
@@ -79,7 +70,7 @@ - (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(N
     const NSInteger sourceItemIndex = sourceIndexPath.item;
     const NSInteger destinationItemIndex = destinationIndexPath.item;
     const NSInteger sourceSectionIndex = sourceIndexPath.section;
-    const NSInteger destinationSectionIndex = destinationIndexPath.section;
+    NSInteger destinationSectionIndex = destinationIndexPath.section;
 
     IGListSectionController *sourceSectionController = [self sectionControllerForSection:sourceSectionIndex];
     IGListSectionController *destinationSectionController = [self sectionControllerForSection:destinationSectionIndex];
@@ -104,7 +95,7 @@ - (void)collectionView:(UICollectionView *)collectionView moveItemAtIndexPath:(N
         } else if (destinationItemIndex == 1 && destinationSectionIndex < sourceSectionIndex) {
             // the "item" representing our section was dropped
             // into the end of a destination section rather than the beginning
-            // so it really belongs one section before the section where it landed
+            // so it really belongs one section after the section where it landed
             destinationSectionIndex += 1;
         }