fixes as per review

Author: kashif

Parse/PFObject.m

@@ -2314,30 +2314,28 @@ - (void)removeObjectForKey:(NSString *)key {
 }
 
 - (void)revert {
-    @synchronized (lock) {
+    @synchronized (self.lock) {
         if ([self isDirty]) {
-            NSMutableArray *removedKeys = [NSMutableArray array];
-            [removedKeys addObjectsFromArray: [self allKeys]];
+            NSMutableSet *persistentKeys = [NSMutableSet setWithArray:[self._state.serverData allKeys]];
+
+            PFOperationSet *unsavedChanges = [self unsavedChanges];
             for (PFOperationSet *operationSet in operationSetQueue) {
-                for (NSString *key in operationSet.keyEnumerator) {
-                    [removedKeys addObject:key];
+                if (operationSet != unsavedChanges) {
+                    [persistentKeys addObjectsFromArray:[operationSet.keyEnumerator allObjects]];
                 }
             }
-            
-            PFOperationSet *changes = [self unsavedChanges];
-            for (NSString *key in changes.keyEnumerator) {
-                [changes removeObjectForKey:key];
-            }
-            
+
+            [unsavedChanges removeAllObjects];
+            [_availableKeys intersectSet:persistentKeys];
+
             [self rebuildEstimatedData];
-            [_availableKeys minusSet:[NSSet setWithArray:removedKeys]];
             [self checkpointAllMutableContainers];
         }
     }
 }
 
 - (void)revertObjectForKey:(NSString *)key {
-    @synchronized (lock) {
+    @synchronized (self.lock) {
         if ([self isDirtyForKey:key]) {
             [[self unsavedChanges] removeObjectForKey:key];
             [self rebuildEstimatedData];

Tests/Unit/ObjectUnitTests.m

@@ -186,7 +186,9 @@ - (void)testKeyValueCoding {
 - (void)testRevert {
     NSDate *date = [NSDate date];
     NSNumber *number = @0.75;
-    PFObject *object = [PFObject _objectFromDictionary:@{ @"yarr" : date, @"score": number } defaultClassName:@"Test" completeData:YES];
+    PFObject *object = [PFObject _objectFromDictionary:@{ @"yarr" : date,
+                                                          @"score": number }
+                                      defaultClassName:@"Test" completeData:YES];
     object[@"yarr"] = @"yolo";
     [object revert];
     XCTAssertEqualObjects(object[@"yarr"], date);