Question

我需要为Core Data对象实现取消/保存行为。我有一个UITableView，我从NSFetchedResultsController获得了数据。

- (void) configureWithCategoryItem: (CategoryItem *) categoryItem
{
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:[CategoryItem entityName]];

    request.predicate = [NSPredicate predicateWithFormat:@"categoryId = %@", categoryItem.categoryId];
    request.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"title" ascending:YES]];

    self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request
                                                                        managedObjectContext:[CategoryItem defaultContext]
                                                                          sectionNameKeyPath:@"title"
                                                                                   cacheName:nil];
    [self.fetchedResultsController performFetch: NULL];
    self.layers = [self categoryLayers];
    self.sectionTitle = categoryItem.title;
}

每次点击此表视图中的单元格

LayerItem *layerItem = [self.layers objectAtIndex:indexPath.row];
layerItem.isSelected = [NSNumber numberWithBool:YES];

在导航栏中我有两个按钮：取消 - 我需要关闭控制器而不将结果保存到核心数据，保存 - 我需要保存结果并关闭控制器

现在，save方法如下所示：

- (void) saveChanges
{
    NSManagedObjectContext *localContext = self.fetchedResultsController.managedObjectContext;
    if ([localContext hasChanges]) {
        [localContext save: NULL];
        [[NSNotificationCenter defaultCenter] postNotificationName:kEADatabaseWasUpdated object:nil];
    }
}

Core Data中是否有某些工具可以帮助我实现这种行为？

我尝试使用单独的NSManagedObjectContext和mergeChangesFromContextDidSaveNotification但未获得好结果。等待您的帮助。

Answer 1

- (void) cancelChanges
{
    NSManagedObjectContext *localContext = self.fetchedResultsController.managedObjectContext;
    [localContext rollback];
}

仅在某些情况下保存NSManagedContext

1 个答案: