NSFetchedResultsController backed UITableViewController with State Restoration

state_restoration.m

#pragma mark - State Restoration

- (NSString *)modelIdentifierForElementAtIndexPath:(NSIndexPath *)idx inView:(UIView *)view {
    if (idx && self.fetchedResultsController) {
        NSManagedObject *object = [self.fetchedResultsController objectAtIndexPath:idx];
        return object.objectID.URIRepresentation.absoluteString;
    }
    return nil;
}

- (NSIndexPath *)indexPathForElementWithModelIdentifier:(NSString *)identifier inView:(UIView *)view {
    if (self.fetchedResultsController) {
        NSURL *objectURL = [NSURL URLWithString:identifier];
        NSPersistentStoreCoordinator *coordinator = self.fetchedResultsController.managedObjectContext.persistentStoreCoordinator;
        NSManagedObjectID *objectID = [coordinator managedObjectIDForURIRepresentation:objectURL];
        NSManagedObject *object =  [self.fetchedResultsController.managedObjectContext existingObjectWithID:objectID error:NULL];
        if (object) {
            return [self.fetchedResultsController indexPathForObject:object];
        }
    }
    return nil;
}