我有一个包含单个部分的提取结果。我可以使用访问对象[[fetchedResultsController fetchedObjects] objectAtIndex:index]对于所有对象。但是当我像这样使用 objectAtIndexPath 时它失败了：[fetchedResultsController objectAtIndexpath:indexPath]
当我将一行（针对一个 SearchResult 对象）插入到相应的表中后，出现错误。该对象似乎已正确插入到新表中。在我目视确认这一点后，我选择其中一行，然后乐趣就开始了。
这是发生错误的代码：
- (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。日志如下所示：
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，我在最后一行使用时出现异常[fetchedResultsController objectAtIndexPath:indexPath]。其他索引值也会发生这种情况，但它们看起来总是有效的。
*** 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），我可以通过一种方法访问每个对象，但不能通过另一种方法访问。 indexPathForObject: 始终返回 (null)。
这是一个错误还是我误解了什么？
UPDATE
这是实现 NSFetchedResultsControllerDelegate 协议方法的代码。
- (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;
}
}
UPDATE 2
我不知道这是否重要，但 tableView 是用这一行初始化的：
tableView = [[UITableView alloc] initWithFrame:CGRectMake(...) style:UITableViewStyleGrouped];
UPDATE 3
当我按如下方式更改有问题的行时，它工作正常。但我宁愿保持索引与表相同。
//SearchResult *result = [self.fetchedResultsController objectAtIndexPath:indexPath];
SearchResult *result = [[self.fetchedResultsController fetchedObjects] objectAtIndex:[indexPath indexAtPosition:1]]
