Don't dirty unchanged records

If any KVO methods get called (e.g., -willChangeValueForKey: and
-didChangeValueForKey:), -isUpdated will return YES even if nothing has
actually changed.

Here, we prune unchanged values from the updates dictionary to ensure
the record will not return YES for -hasChanges unless values change in
the first place.

Signed-off-by: Stephen Celis <stephen@stephencelis.com>

Author: stephencelis

Classes/NSManagedObject+ActiveRecord.m

@@ -64,7 +64,7 @@ + (instancetype)findOrCreate:(NSDictionary *)properties {
 }
 
 + (instancetype)findOrCreate:(NSDictionary *)properties inContext:(NSManagedObjectContext *)context {
-    NSDictionary *transformed = [[self class] transformProperties:properties withContext:context];
+    NSDictionary *transformed = [[self class] transformProperties:properties withObject:nil context:context];
 
     NSManagedObject *existing = [self where:transformed inContext:context].first;
     return existing ?: [self create:transformed inContext:context];
@@ -172,7 +172,7 @@ + (id)createInContext:(NSManagedObjectContext *)context {
 - (void)update:(NSDictionary *)attributes {
     unless([attributes exists]) return;
 
-    NSDictionary *transformed = [[self class] transformProperties:attributes withContext:self.managedObjectContext];
+    NSDictionary *transformed = [[self class] transformProperties:attributes withObject:self context:self.managedObjectContext];
 
     for (NSString *key in transformed) [self willChangeValueForKey:key];
     [transformed each:^(NSString *key, id value) {
@@ -207,7 +207,7 @@ + (NSString *)entityName {
 
 #pragma mark - Private
 
-+ (NSDictionary *)transformProperties:(NSDictionary *)properties withContext:(NSManagedObjectContext *)context {
++ (NSDictionary *)transformProperties:(NSDictionary *)properties withObject:(NSManagedObject *)object context:(NSManagedObjectContext *)context {
     NSEntityDescription *entity = [NSEntityDescription entityForName:[self entityName] inManagedObjectContext:context];
 
     NSDictionary *attributes = [entity attributesByName];
@@ -218,7 +218,13 @@ + (NSDictionary *)transformProperties:(NSDictionary *)properties withContext:(NS
     for (NSString *key in properties) {
         NSString *localKey = [self keyForRemoteKey:key inContext:context];
         if (attributes[localKey] || relationships[localKey]) {
-            transformed[localKey] = [[self class] transformValue:properties[key] forRemoteKey:key inContext:context];
+            id value = [[self class] transformValue:properties[key] forRemoteKey:key inContext:context];
+            if (object) {
+                id localValue = [object primitiveValueForKey:localKey];
+                if ([localValue isEqual:value] || (localValue == nil && value == [NSNull null]))
+                    continue;
+            }
+            transformed[localKey] = value;
         } else {
 #if DEBUG
             NSLog(@"Discarding key ('%@') from properties on class ('%@'): no attribute or relationship found",

Example/SampleProjectTests/FindersAndCreatorsTests.m

@@ -312,6 +312,12 @@ void createSomePeople(NSArray *names, NSArray *surnames, NSManagedObjectContext
             }];
             [[[Person where:@{ @"firstName": @"asetnset" }] should] haveCountOf:1];
         });
+
+        it(@"doesn't mark records as having changes when values are the same", ^{
+            Person *person = fetchUniquePerson();
+            [person update:@{@"firstName": person.firstName}];
+            [[@([person hasChanges]) should] beNo];
+        });
     });
 
     context(@"Saving", ^{