How to Insert Core Data Record Related to Another Without Duplication

I have two core data entities, Articles and Favorite. Articles has To-Many relationship to Favorite. First, I inserted all Articles object successfully.

Now, I'm trying to insert ArticleID in “Favorite” entity but I cant. Either the record is inserted with an empty relationship or it is inserted with new record in “Articles” entity.

I think that I should be getting the related record in Articles entity first and then using it to insert in Favorite but I'm not sure how to do this. My current code:

NSManagedObjectContext *context =[appDelegate managedObjectContext] ; 
favorite *Fav =[NSEntityDescription insertNewObjectForEntityForName:@"favorite" inManagedObjectContext:context];
Articles * Article = [NSEntityDescription insertNewObjectForEntityForName:@"Articles" inManagedObjectContext:context];

NSError *error;

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 
NSEntityDescription *entity = [NSEntityDescription 
                               entityForName:@"Articles" inManagedObjectContext:context];  
[fetchRequest setEntity:entity]; 
NSPredicate *secondpredicate = [NSPredicate predicateWithFormat:@"qid = %@",appDelegate.GlobalQID ];
NSPredicate *thirdpredicate = [NSPredicate predicateWithFormat:@"LangID=%@",appDelegate.LangID]; 
NSPredicate *comboPredicate = [NSCompoundPredicate andPredicateWithSubpredicates:[NSArray arrayWithObjects: secondpredicate,thirdpredicate, nil]]; 
[fetchRequest setPredicate:comboPredicate];
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
for (NSManagedObject *info in fetchedObjects) { 
        // ?????????????????????????

    }

}

Any suggestions would be appreciated.