iPhone Coredata error (NSMergeConflict for NSManagedObject)

Question

Sometimes i have this error with coredata in the same place. Sometimes its ok, and in other time i have this error. What does it mean? I can't find anything about it :(

ps sorry for my english :)

conflictList = ( "NSMergeConflict (0xd447640) for NSManagedObject (0xd41b370) with objectID '0xd41b500 ' with oldVersion = 4 and newVersion = 5 and old object snapshot = {\n album = \"{(\n)}\";\n audios = \"{(\n)}\";\n bdate = \"\";\n city = \"\";\n country = \"\";\n dialog = \"{(\n)}\";\n domain = \"white.smoke\";\n faculty = 0;\n facultyName = \"\";\n firstName = White;\n graduation = 0;\n homePhone = \"\";\n isFriend = 1;\n isMe = 0;\n lastName = Smoke;\n mobilePhone = \"\";\n nickName = \"\";\n online = 1;\n photo = \"\";\n photoBig = \"\";\n photoComments = \"{(\n)}\";\n photoMedium = \"\";\n photoRec = \"http://cs10609.vkontakte.ru/u79185807/e_8c949409.jpg\";\n photos = \"{(\n (entity: Photo; id: 0xd482c50 ; data: {\n aid = 121594781;\n album = nil;\n comments = \\"\\";\n commentsCount = 0;\n created = \\"2010-12-10 03:45:01 GMT\\";\n owner = \\"0xd41b500 \\";\n \\"owner_id\\" = 79185807;\n photosNumber = 0;\n pid = 196997145;\n src = \\"http://cs10609.vkontakte.ru/u79185807/121594781/m_\\";\n \\"src_big\\" = \\"http://cs10609.vkontakte.ru/u79185807/121594781/x_\\";\n \\"src_small\\" = \\"http://cs10609.vkontakte.ru/u79185807/121594781/s_\\";\n \\"src_xbig\\" = nil;\n \\"src_xxbig\\" = nil;\n wallRel = \\"0xd480840 \\";\n}),\n (entity: Photo; id: 0xd431570 ; data: {\n aid = 121594781;\n album = nil;\n comments = \\"\\";\n commentsCount = 0;\n created = \\"2010-12-10 03:43:01 GMT\\";\n owner = \\"0xd41b500 \\";\n \\"owner_id\\" = 79185807;\n photosNumber = 0;\n pid = 196997029;\n src = \\"http://cs10609.vkontakte.ru/u79185807/121594781/m_\\";\n \\"src_big\\" = \\"http://cs10609.vkontakte.ru/u79185807/121594781/x_\\";\n \\"src_small\\" = \\"http://cs10609.vkontakte.ru/u79185807/121594781/s_\\";\n \\"src_xbig\\" = nil;\n \\"src_xxbig\\" = nil;\n wallRel = \\"0xd42d500 \\";\n})\n)}\";\n rate = \"-19\";\n sex = 0;\n statuses = \"{(\n)}\";\n timezone = 0;\n uid = 79185807;\n university = 0;\n universityName = \"\";\n videos = \"{(\n)}\";\n wall = \"{(\n)}\";\n wallPostsCount = 0;\n wallReplies = \"{(\n (entity: WallReply; id: 0xd448270 ; data: )\n)}\";\n wallSender = \"{(\n)}\";\n} and new cached row = {\n bdate = \"\";\n city = \"\";\n country = \"\";\n domain = \"white.smoke\";\n faculty = 0;\n facultyName = \"\";\n firstName = White;\n graduation = 0;\n homePhone = \"\";\n isFriend = 1;\n isMe = 0;\n lastName = Smoke;\n mobilePhone = \"\";\n nickName = \"\";\n online = 1;\n photo = \"\";\n photoBig = \"\";\n photoMedium = \"\";\n photoRec = \"http://cs10609.vkontakte.ru/u79185807/e_8c949409.jpg\";\n rate = \"-19\";\n sex = 0;\n timezone = 0;\n uid = 79185807;\n university = 0;\n universityName = \"\";\n wallPostsCount = 0;\n}" );

Answer 1

A merge conflict sometimes results when your database gets changed from two different places, then saved from two different places; in certain cases, the changes might affect the same objects or properties, and Core Data doesn't automatically overwrite them, as that might destroy valuable data.

There are a few options:

• When you get a merge conflict, iterate through its information, and manually resolve any conflicts according to the needs of your application.
• Set the merge policy of the managed object context(s) to one that will automatically resolve certain kinds of conflicts. Some merge policies are partially destructive, some are very destructive – which one is right really depends on your application and the importance of the data being saved.
• Use mergeChangesFromContextDidSaveNotification: to quickly and closely integrate changes into managed object contexts that haven't been saved yet. Note that this may still require some level of conflict resolution, but should help minimize the severity.

Answer 2

In short - enable Merge Policy add this to your MOC setup:

objective-C

[_managedObjectContext setMergePolicy:[[NSMergePolicy alloc] initWithMergeType:NSMergeByPropertyObjectTrumpMergePolicyType]]; 

Swift

 lazy var managedObjectContext: NSManagedObjectContext? = {      let coordinator = self.persistentStoreCoordinator     if coordinator == nil {         return nil     }     var managedObjectContext = NSManagedObjectContext()     managedObjectContext.persistentStoreCoordinator = coordinator      //add this line      managedObjectContext.mergePolicy = NSMergePolicy(mergeType: NSMergePolicyType.MergeByPropertyObjectTrumpMergePolicyType);      return managedObjectContext }()