删除对象时为null indexPaths

我搞不清楚,但当我从 NSFetchedResultsController .

当我删除我的对象时,我会这样做:

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete the object
        NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
        [context deleteObject:[self.fetchedResultsController objectAtIndexPath:indexPath]];

        [self saveContext];
    }
}

设置 NSFetchedResults控制器 :

- (NSFetchedResultsController *)fetchedResultsController {
    if (_fetchedResultsController != nil) {
        return _fetchedResultsController;
    }
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    [fetchRequest setFetchBatchSize:20];

    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Route" inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];

    NSSortDescriptor *nameSort = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES selector:@selector(localizedCaseInsensitiveCompare:)];
    NSArray *sortDescriptors = @[nameSort];
    [fetchRequest setSortDescriptors:sortDescriptors];

    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:@"Routes"];
    self.fetchedResultsController = aFetchedResultsController;
    self.fetchedResultsController.delegate = self;

    NSError *error = nil;
    if (![self.fetchedResultsController performFetch:&error]) {
        NSLog(@"Unresolved error with NSFetchedResultsController: %@", [error description]);
        abort();
    }

    return _fetchedResultsController;
}

这就是故障发生的地方:

- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {

    switch (type) {
            // Data was inserted - insert the data into the table view
        case NSFetchedResultsChangeInsert: {
            [self.savedRoutesTableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationAutomatic];

            break;
        }
            // Data was deleted - delete the data from the table view
        case NSFetchedResultsChangeDelete: {
            [self.savedRoutesTableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
            break;
        }
        case NSFetchedResultsChangeUpdate: {
            SavedRoutesTableViewCell *cell = (SavedRoutesTableViewCell *)[self.savedRoutesTableView cellForRowAtIndexPath:indexPath];
            [cell configureCellWithRoute:[controller objectAtIndexPath:newIndexPath]];
            break;
        }
        case NSFetchedResultsChangeMove: {
            [self.savedRoutesTableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
            [self.savedRoutesTableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
            break;
        }
        default:
            break;
    }
}

在didChangeObject方法中,我的indexPath和newIndexPath都为nil。我可以NSLog我的对象,并且我确实看到了实体。它在 [self.savedRoutesTableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic]; 方法,但出现异常:

CoreData: error: Serious application error.  Exception was caught during Core Data change processing.  This is usually a bug within an observer of NSManagedObjectContextObjectsDidChangeNotification.  *** -[__NSPlaceholderArray initWithObjects:count:]: attempt to insert nil object from objects[0] with userInfo (null)

当我保存这个对象时,我会这样保存它:

self.route.name = routeName;
NSManagedObjectContext *tempContext = [self.route managedObjectContext];

[tempContext performBlock:^{
        NSError *error = nil;
        if (![tempContext save:&error]) {
            NSLog(@"an error occurred: %@", [error localizedDescription]);
        }

        [self.managedObjectContext performBlock:^{
            NSError *error = nil;
            if (![_managedObjectContext save:&error]) {
                NSLog(@"error in main context: %@", [error localizedDescription]);
            }
        }];
    }];

由于 NSFetchedResults控制器 只是没有给我返回已删除对象的indexPath。有什么想法吗?提前谢谢。

编辑: 我找到了导致错误的罪魁祸首,但我不确定为什么会这样。基本上,我有一个ViewController,如果它正在编辑路线,它会从主主运行中心接收一个路线实体,或者如果你正在创建一个新路线,它就会插入一个新实体。因此,在那个viewController中,如果我正在编辑一个路由,因为我试图使用两个MOC,一个temp,一个main作为它的父级,这样如果用户决定取消而不创建新的路由,我可以很容易地丢弃东西,我需要将该路由转移到另一个上下文,以使我拥有的其他代码工作。因此,“转移”看起来像:

    NSManagedObjectContext *moc = _route.managedObjectContext;
    NSManagedObjectID *routeId = [_route objectID];
    self.tempContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
    self.tempContext.parentContext = moc;
    NSManagedObject *localRoute = [self.tempContext objectWithID:routeId];
    self.route = localRoute;

有了这个代码,我在现有路线上添加位置是可行的,因为这些位置在相同的上下文中,但不知何故,它会把从主运行中心删除现有路线搞砸。不确定为什么以及最好的解决方案是什么。