CoreData NSSet-Like behavior for NSManagedObjects with the same values

Question

I have a Chat-App with a Data-Modell like this.

User <--> Conversation <-->> Message

My Problem now: Sometimes, if I get old messages from a Backup, I have Messages twice in my DataModel. I'd like to have a NSSet-Like Class which recognizes, if a Message-Object has exactly the same values on it's properties. I've read, that I must not override the methods -hash and -isEqual:, so I don't know how to do it. Any Idea? Here is some code...

+(void)addMessages:(NSSet<JSQMessage *> *)messages toConversation:(Conversation *)conversation
{
    DataManager * dataManager = [DataManager dataManager];
    NSMutableSet * storeSet = [NSMutableSet setWithCapacity:messages.count];

for (JSQMessage * jsqMessage in messages) {
    Message * message = [NSEntityDescription insertNewObjectForEntityForName:CDEntityNameMessage inManagedObjectContext:[dataManager managedObjectContext]];
    message.senderId = jsqMessage.senderId;
    message.senderDisplayName = jsqMessage.senderDisplayName;
    message.text = jsqMessage.text;
    message.date = jsqMessage.date;
    [storeSet addObject:message];
}
[conversation addMessages:storeSet];

NSError *error;
if (![[dataManager managedObjectContext] save:&error]) {
    NSLog(@"Something went wrong: %@", [error localizedDescription]);
} else {
    //Saved successfull
}
}

And the Conversation -addMessages: Method is the one automatically generated from Xcode/CoreData

- (void)addMessages:(NSSet<Message *> *)values;

Answer 1

What I do now is checking manually, if there is a Object with same Attributes in my MOC. If there is one, I skip the creation. I know, it is a bit inefficient but with my expected number of messages, this should be no problem.

NSFetchRequest * fr = [NSFetchRequest fetchRequestWithEntityName:CDEntityNameMessage];
  [fr setPredicate:[NSPredicate predicateWithFormat:@"text == %@ AND date == %@ AND conversation.user.objectId == %@", message.text, message.date, chatpartner.objectId]];
  NSArray * results = [[self managedObjectContext] executeFetchRequest:fr error:nil];
  if (results && results.count > 0) {
     continue;
  }