NSFetchedResultsController objectAtIndex,objectAtIndexPath,indexPathForObject不一致

Question

我有一个部分的获取结果.我可以使用[[fetchedResultsController fetchedObjects] objectAtIndex:index]所有对象访问对象.但是当我像这样使用objectAtIndexPath时失败了:[fetchedResultsController objectAtIndexpath:indexPath]

将一行(对于其中一个SearchResult对象)插入相应的表后发生错误.该对象似乎正确插入到新表中.在我直观地确认了这一点之后,我选择了其中一行,然后开始了.

以下是发生错误的代码:

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    SearchResult *event;
    NSLog(@"Number of sections in fetchedResultsController: %d", [[fetchedResultsController sections] count]);
    for (NSUInteger i=0; i<[[fetchedResultsController fetchedObjects] count]; i++) {
        event = (SearchResult*)[[fetchedResultsController fetchedObjects] objectAtIndex:i];
        NSLog(@"object at index[%d]: %@", i, event.title );
        NSLog(@"indexPath for object at index[%d]:%@", i, [fetchedResultsController indexPathForObject:event]);
    }

    NSLog(@"indexPath passed to method: %@", indexPath);

    SearchResult *result = [fetchedResultsController objectAtIndexPath:indexPath];  // *** here is where the error occurs ***

    [viewDelegate getDetails:result];
}

我在最后一行失败了.日志看起来像这样:

Number of sections in fetchedResultsController: 1
object at index[0]: Cirles
indexPath for object at index[0]:(null)
object at index[1]: Begin
indexPath for object at index[1]:(null)
object at index[2]: Copy
indexPath for object at index[2]:(null)
object at index[3]: Unbound
indexPath for object at index[3]:(null)
indexPath passed to method: <NSIndexPath 0x64ddea0> 2 indexes [0, 2]

执行NSLog语句后,我在最后一行使用了一个异常[fetchedResultsController objectAtIndexPath:indexPath].它也适用于其他索引值,但它们总是看起来有效.

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'no object at index 2 in section at index 0'

因此,总而言之,似乎有正确数量的获取对象,有一个部分(0),我可以通过一个方法访问每个,但不能通过另一个方法访问.indexPathForObject:始终返回(null).

这是一个错误还是我误解了什么？

---

UPDATE

这是代码,实现了NSFetchedResultsControllerDelegate协议方法.

- (void) controllerWillChangeContent:(NSFetchedResultsController *)controller {
    NSLog(@"Favorites controllerWillChangeContent");
    [self.tableView beginUpdates];
}

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller 
{
    NSLog(@"Favorites Table controllerDidChangeContent");
    [self.tableView endUpdates];
}

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

    NSLog(@"Favorites Changed Object");

    switch (type) {
        case NSFetchedResultsChangeInsert:
            NSLog(@"--- Favorite was inserted");
            if ([[self.fetchedResultsController fetchedObjects] count] == 1) {
                // configure first cell to replace the empty list indicator by first deleting the "empty" row
                [self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationNone];
            }

            [self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationNone];

            break;

        case NSFetchedResultsChangeDelete:
            NSLog(@"--- Favorite was deleted");

            [self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationNone];
            if ([[self.fetchedResultsController fetchedObjects] count] == 0) {
                // configure first cell to show that we have an empty list
                [self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationNone];
            }

            break;

        case NSFetchedResultsChangeMove:
            NSLog(@"--- Favorite was moved");

            break;

        case NSFetchedResultsChangeUpdate:
            NSLog(@"--- Favorite was updated");
            [self configureCell:(ResultCell*)[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];

            break;

        default:
            break;
    }

}

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

    switch (type) {
        case NSFetchedResultsChangeInsert:
            NSLog(@"Favorites Section Added");

            break;

        case NSFetchedResultsChangeDelete:
            NSLog(@"Favorites Section Deleted");

            break;

        default:
            break;
    }

}

---

更新2

我不知道它是否重要,但tableView是用这一行初始化的:

    tableView = [[UITableView alloc] initWithFrame:CGRectMake(...) style:UITableViewStyleGrouped];

---

更新3

当我按如下方式改变违规行时,它工作正常.但我宁愿保持索引与表格相同.

//SearchResult *result = [self.fetchedResultsController objectAtIndexPath:indexPath];
SearchResult *result = [[self.fetchedResultsController fetchedObjects] objectAtIndex:[indexPath indexAtPosition:1]]

Answer 1

我现在也有同样的问题。

对我来说，它有助于NSFetchedResultsController初始化cacheName: nil。