Expose NewModifiedIndices (#1752)

* Expose NewModifiedIndices

* Changelog

CHANGELOG.md

@@ -2,6 +2,9 @@
 ------------------
 
 ### Enhancements
+- Exposed a `ChangeSet.NewModifiedIndices` collection that contains information about the
+indices of the objects that changed in the new version of the collection (i.e. after
+accounting for the insertions and deletions).
 
 ### Bug fixes
 - `WriteAsync` will no longer perform a synchronous `Refresh` on the main thread. ([#1729](https://github.com/realm/realm-dotnet/pull/1729))

Realm/Realm/Handles/NotifiableObjectHandleBase.cs

@@ -29,6 +29,7 @@ internal struct CollectionChangeSet
             public MarshaledVector<IntPtr> Deletions;
             public MarshaledVector<IntPtr> Insertions;
             public MarshaledVector<IntPtr> Modifications;
+            public MarshaledVector<IntPtr> Modifications_New;
 
             [StructLayout(LayoutKind.Sequential)]
             public struct Move

Realm/Realm/Linq/IRealmCollection.cs

@@ -35,13 +35,21 @@ public class ChangeSet
         public int[] InsertedIndices { get; }
 
         /// <summary>
-        /// Gets the indices in the new version of the <see cref="IRealmCollection{T}"/> which were modified.
+        /// Gets the indices in the *old* version of the <see cref="IRealmCollection{T}"/> which were modified.
         /// This means that either the property of an object at that index was modified or the property of
         /// of an object it's related to has changed.
         /// </summary>
         /// <value>An array, containing the indices of the modified objects.</value>
         public int[] ModifiedIndices { get; }
 
+        /// <summary>
+        /// Gets the indices in the *new* version of the <see cref="IRealmCollection{T}"/> which were modified.
+        /// Conceptually, it contains the same entries as <see cref="ModifiedIndices"/> but after the insertions
+        /// and deletions have been accounted for.
+        /// </summary>
+        /// <value>An array, containing the indices of the modified objects.</value>
+        public int[] NewModifiedIndices { get; }
+
         /// <summary>
         /// Gets the indices of objects in the previous version of the <see cref="IRealmCollection{T}"/> which have been removed from this one.
         /// </summary>
@@ -58,10 +66,11 @@ public class ChangeSet
         /// <value>An array of <see cref="Move"/> structs, indicating the source and the destination index of the moved row.</value>
         public Move[] Moves { get; }
 
-        internal ChangeSet(int[] insertedIndices, int[] modifiedIndices, int[] deletedIndices, Move[] moves)
+        internal ChangeSet(int[] insertedIndices, int[] modifiedIndices, int[] newModifiedIndices, int[] deletedIndices, Move[] moves)
         {
             InsertedIndices = insertedIndices;
             ModifiedIndices = modifiedIndices;
+            NewModifiedIndices = newModifiedIndices;
             DeletedIndices = deletedIndices;
             Moves = moves;
         }

Realm/Realm/RealmCollectionBase.cs

@@ -348,6 +348,7 @@ void NotificationsHelper.INotifiable.NotifyCallbacks(NotifiableObjectHandleBase.
                 changeset = new ChangeSet(
                     insertedIndices: actualChanges.Insertions.AsEnumerable().Select(i => (int)i).ToArray(),
                     modifiedIndices: actualChanges.Modifications.AsEnumerable().Select(i => (int)i).ToArray(),
+                    newModifiedIndices: actualChanges.Modifications_New.AsEnumerable().Select(i => (int)i).ToArray(),
                     deletedIndices: actualChanges.Deletions.AsEnumerable().Select(i => (int)i).ToArray(),
                     moves: actualChanges.Moves.AsEnumerable().Select(m => new ChangeSet.Move((int)m.From, (int)m.To)).ToArray());
             }

Tests/Tests.Shared/NotificationTests.cs

@@ -700,6 +700,46 @@ void helper(IRealmCollection<Person> _, ChangeSet changes, Exception __)
             });
         }
 
+        [Test]
+        public void ModifiedIndices_ReportCorrectlyForOldAndNewVersions()
+        {
+            ChangeSet changes = null;
+            void cb(IRealmCollection<IntPrimaryKeyWithValueObject> s, ChangeSet c, Exception e) => changes = c;
+
+            var toDelete = new IntPrimaryKeyWithValueObject { Id = 1 };
+            var toModify = new IntPrimaryKeyWithValueObject { Id = 2 };
+
+            _realm.Write(() =>
+            {
+                _realm.Add(toDelete);
+                _realm.Add(toModify);
+            });
+
+            var query = _realm.All<IntPrimaryKeyWithValueObject>().OrderBy(i => i.Id);
+            using (query.SubscribeForNotifications(cb))
+            {
+                Assert.That(query.ElementAt(0).Equals(toDelete));
+                Assert.That(query.ElementAt(1).Equals(toModify));
+
+                _realm.Write(() =>
+                {
+                    _realm.Remove(toDelete);
+                    toModify.StringValue = "newValue";
+                });
+
+                _realm.Refresh();
+                Assert.That(changes, Is.Not.Null);
+                Assert.That(changes.DeletedIndices, Is.EquivalentTo(new int[] { 0 }));
+
+                // Modified should be in the old collection
+                Assert.That(changes.ModifiedIndices, Is.EquivalentTo(new int[] { 1 }));
+
+                // NewModified should be in the new collection that is just 1 element
+                Assert.That(changes.NewModifiedIndices, Is.EquivalentTo(new int[] { 0 }));
+                Assert.That(query.ElementAt(changes.NewModifiedIndices[0]).Equals(toModify));
+            }
+        }
+
         public static IEnumerable<TestCaseData> CollectionChangedTestCases()
         {
             yield return new TestCaseData(new int[] { }, NotifyCollectionChangedAction.Add, new int[] { 1 }, 0);

wrappers/src/notifications_cs.hpp

@@ -32,7 +32,8 @@ namespace realm {
         MarshallableIndexSet deletions;
         MarshallableIndexSet insertions;
         MarshallableIndexSet modifications;
-
+        MarshallableIndexSet modifications_new;
+
         struct {
             CollectionChangeSet::Move* moves;
             size_t count;
@@ -88,6 +89,7 @@ namespace realm {
             auto deletions = get_indexes_vector(changes.deletions);
             auto insertions = get_indexes_vector(changes.insertions);
             auto modifications = get_indexes_vector(changes.modifications);
+            auto modifications_new = get_indexes_vector(changes.modifications_new);
 
             std::vector<size_t> properties;
 
@@ -101,6 +103,7 @@ namespace realm {
                 { deletions.data(), deletions.size() },
                 { insertions.data(), insertions.size() },
                 { modifications.data(), modifications.size() },
+                { modifications_new.data(), modifications_new.size() },
                 { changes.moves.data(), changes.moves.size() },
                 { properties.data(), properties.size() }
             };