Merge pull request #55 from terenzeyuen/fix-move-conflicts

Fix move conflicts

Author: lightsprint09

Sourcing/FetchedResultsDataProvider.swift

@@ -45,7 +45,7 @@ open class FetchedResultsDataProvider<Object: NSFetchRequestResult>: NSObject, N
         configure(fetchedResultsController)
 
         try fetchedResultsController.performFetch()
-        dataProviderDidChangeContets(with: nil)
+        dataProviderDidChangeContents(with: nil)
     }
 
     public func object(at indexPath: IndexPath) -> Object {
@@ -102,18 +102,31 @@ open class FetchedResultsDataProvider<Object: NSFetchRequestResult>: NSObject, N
     }
 
     public func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
-        dataProviderDidChangeContets(with: updates)
-        let updatesByMoves = updates.map({ (operation: DataProviderUpdate<Object>) -> DataProviderUpdate<Object>? in
+        let updatesIndexPaths = updates.flatMap { update -> IndexPath? in
+            switch update {
+            case .update(let indexPath, _):
+                return indexPath
+            default: return nil
+            }
+        }
+        updates = updates.flatMap { update -> DataProviderUpdate<Object>? in
+            if case .move(_, let newIndexPath) = update, updatesIndexPaths.contains(newIndexPath) {
+               return nil
+            }
+            return update
+        }
+        dataProviderDidChangeContents(with: updates)
+        let updatesByMoves = updates.flatMap { operation -> DataProviderUpdate<Object>? in
             if case .move(_, let newIndexPath) = operation {
                 return .update(newIndexPath, object(at: newIndexPath))
             }
             return nil
-        }).flatMap { $0 }
-        dataProviderDidChangeContets(with: updatesByMoves)
+        }
+        dataProviderDidChangeContents(with: updatesByMoves)
     }
 
-    func dataProviderDidChangeContets(with updates: [DataProviderUpdate<Object>]?, triggerdByTableView: Bool = false) {
-        if !triggerdByTableView {
+    func dataProviderDidChangeContents(with updates: [DataProviderUpdate<Object>]? = nil, triggeredByTableView: Bool = false) {
+        if !triggeredByTableView {
             whenDataProviderChanged?(updates)
         }
         dataProviderDidUpdate?(updates)

SourcingTests/FetchedResultsDataProviderTests.swift

@@ -198,6 +198,26 @@ class FetchedResultsDataProviderTests: XCTestCase {
         }
     }
 
+    func testConflictIndexPathsForMoveUpdate() {
+        //Given
+        let updateIndexPath = IndexPath(row: 1, section: 0)
+        let oldIndexPath = IndexPath(row: 0, section: 0)
+        let newIndexPath = IndexPath(row: 1, section: 0)
+        
+        //When
+        dataProvider.controller(fetchedResultsController as! NSFetchedResultsController<NSFetchRequestResult>,
+                                didChange: 1, at: oldIndexPath, for: .move, newIndexPath: newIndexPath)
+        dataProvider.controller(fetchedResultsController as! NSFetchedResultsController<NSFetchRequestResult>,
+                                didChange: 1, at: updateIndexPath, for: .update, newIndexPath: nil)
+        dataProvider.controllerDidChangeContent(fetchedResultsController as! NSFetchedResultsController<NSFetchRequestResult>)
+        
+        //Then
+        XCTAssertEqual(dataProvider.updates.count, 1)
+        if case .move = dataProvider.updates.first! {
+            XCTFail()
+        }
+    }
+    
     func testProcessUpdates() {
         //Given
         var didUpdateNotification = false