nsFetchedResultsController:在更新期间使用nsManagedObjectContext会导致崩溃

以下是我的控制器类的接口:

@interface ProjectListViewController : UITableViewController <NSFetchedResultsControllerDelegate> {
    NSFetchedResultsController *fetchedResultsController;
    NSManagedObjectContext *managedObjectContext;
}

@end

我用以下代码初始化 提取结果控制器 :

if (fetchedResultsController != nil) {
    return fetchedResultsController;
}

    // Create and configure a fetch request with the Project entity.
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Project" inManagedObjectContext:managedObjectContext];
    [fetchRequest setEntity:entity];

    // Create the sort descriptors array.
    NSSortDescriptor *projectIdDescriptor = [[NSSortDescriptor alloc] initWithKey:@"projectId" ascending:YES];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:projectIdDescriptor, nil];
    [fetchRequest setSortDescriptors:sortDescriptors];

    // Create and initialize the fetch results controller.
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
                                                                                            managedObjectContext:managedObjectContext 
                                                                                              sectionNameKeyPath:nil 
                                                                                                       cacheName:nil];
    self.fetchedResultsController = aFetchedResultsController;
    fetchedResultsController.delegate = self;

如你所见,我也在用 管理对象上下文 在我的控制器类中定义

以下采用了控制删除协议中的nsfetchedresults:

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
    // The fetch controller is about to start sending change notifications, so prepare the table view for updates.
        [self.tableView beginUpdates];
}


- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
        UITableView *tableView = self.tableView;

        switch(type) {

            case NSFetchedResultsChangeInsert:
                [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
                break;

            case NSFetchedResultsChangeDelete:
                [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
                break;

            case NSFetchedResultsChangeUpdate:
                [self _configureCell:(TDBadgedCell *)[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
                break;

            case NSFetchedResultsChangeMove:
                if (newIndexPath != nil) {
                    [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
                    [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
                }
                else {
                    [tableView reloadSections:[NSIndexSet indexSetWithIndex:indexPath.section] withRowAnimation:UITableViewRowAnimationFade];
                }
            break;
        }
}


- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
        switch(type) {

            case NSFetchedResultsChangeInsert:
                [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
                break;

            case NSFetchedResultsChangeDelete:
                [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
                break;
        }
}


- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
        [self.tableView endUpdates];
}

在_configureCell:atindexpath:方法中,我有以下代码:

    NSFetchRequest *issuesNumberRequest = [NSFetchRequest new];
    NSEntityDescription *issueEntity = [NSEntityDescription entityForName:@"Issue" inManagedObjectContext:managedObjectContext];
    [issuesNumberRequest setEntity:issueEntity];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"projectId == %@", project.projectId];
    [issuesNumberRequest setPredicate:predicate];
    NSUInteger issuesNumber = [managedObjectContext countForFetchRequest:issuesNumberRequest error:nil];
    [issuesNumberRequest release];

我再次使用ManagedObjectContext。

但当我尝试插入新项目时,应用程序崩溃,出现以下异常:

-[UITableView中的断言失败 _ endcellanimationswithcontext:,/sourcecache/uikit_-sim/uikit-984.38/uitableview.m:774 由于未捕获而终止应用程序 例外 'nsInternalConsistenceyException', 原因:'无效更新:无效 第0节中的行数。这个 中包含的行数 更新后的现有部分(4) 必须等于行数 包含在该节之前 更新(4),加上或减去数字 从中插入或删除的行数 节(插入1,删除0)。'

幸运的是,我找到了一个解决方法:如果我在_configureCell:atindexpath:method app中创建和使用单独的nsmanagedObjectContext,那么它不会崩溃!

我只想知道,这种行为是否正确?

Here is a sample project. 注意crashmeViewController的“_configureCell:atindexpath:”和“_addsomerows”方法