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这是我的控制器类的接口：

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

@end

我使用以下代码来初始化fetchedResultsController：

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;

如您所见，我使用的是与控制器类中定义的相同的managedObjectContext

这是 NSFetchedResultsControllerDelegate 协议的采用：

- (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: 方法内部，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 。

但是当我尝试插入新项目时，应用程序崩溃并出现以下异常：

-[UITableView _endCellAnimationsWithContext:] 中的断言失败，/SourceCache/UIKit_Sim/UIKit-984.38/UITableView.m:774 由于未捕获的异常“NSInternalInconsistencyException”而终止应用程序，原因：“无效更新：第 0 节中的行数无效。数量更新后现有节中包含的行数 (4) 必须等于更新前该节中包含的行数 (4)，加上或减去从该节中插入或删除的行数（1 插入，0已删除）。

幸运的是，我找到了一种解决方法：如果我在 _configureCell:atIndexPath: 方法中创建并使用单独的 NSManagedObjectContext: 方法应用程序不会崩溃！

我只想知道，这种行为是否正确？

这是一个示例项目。 注意 CrashMeViewController 的 '_configureCell:atIndexPath:' 和 '_addSomeRows' 方法

4

1 回答 1

0

在 iOS 4.0 中已修复

于 2010-06-22T09:58:51.613 回答