NSFetchedResultsController objectAtIndex，objectAtIndexPath，indexPathForObject inconsistencies [英] NSFetchedResultsController objectAtIndex, objectAtIndexPath, indexPathForObject inconsistencies
问题描述
我有一个部分的抓取结果。我可以使用 [[fetchedResultsController fetchedObjects] objectAtIndex：index] 访问所有对象的对象。但是当我使用objectAtIndexPath这样的时候，它是失败的： [fetchedResultsController objectAtIndexpath：indexPath]
将一行（对于一个SearchResult对象）插入到相应的表中。该对象似乎被正确插入到新表中。
这是发生错误的代码：
- （void）tableView：（UITableView *）tableView didSelectRowAtIndexPath：（NSIndexPath *）indexPath
{
SearchResult * event;
NSLog（@fetchedResultsController中的节数：％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传递给方法：％@，indexPath）;
SearchResult * result = [fetchedResultsController objectAtIndexPath：indexPath]; // ***这里是错误发生的地方***
[viewDelegate getDetails：result];
}
我在最后一行出现故障。日志如下所示：
在fetchedResultsController中的节数：1
在索引[0]处的对象：Cirles
indexPath对象在index [0] :( null）
对象在索引[1]：Begin
indexPath对象在索引[1] :( null）
对象在索引[2]：复制
indexPath索引处的对象[2] :( null）
索引处的对象[3]：未绑定
indexPath索引处的对象[3] :( null）
indexPath传递给方法：< NSIndexPath 0x64ddea0> 2 index [0，2]
执行NSLog语句后，使用 [fetchedResultsController objectAtIndexPath：indexPath] 。
***由于未捕获异常NSInternalInconsistencyException而终止应用程序，原因： '在索引0处的索引2处没有对象'
因此，总而言之，似乎存在正确数量的获取对象，有一个部分（0），我可以访问每一个一个方法，但不是由另一个。 indexPathForObject：总是返回（null）。
这是一个错误还是我误解了什么？
UPDATE
这是代码，实现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）{
//配置第一个单元格来替换空列表指针，首先删除空行
[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）{
//配置第一个单元格以显示我们有一个空列表
[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;
默认值：
break;
}
}
- （void）controller：（NSFetchedResultsController *）controller
didChangeSection：（id< NSFetchedResultsSectionInfo>）sectionInfo
atIndex：（NSUInteger）sectionIndex
forChangeType：（NSFetchedResultsChangeType）type {
switch（type）{
case NSFetchedResultsChangeInsert：
NSLog ）;
break;
case NSFetchedResultsChangeDelete：
NSLog（@收藏夹部分已删除）;
break;
默认值：
break;
}
}
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UPDATE 2
我不知道是否重要，但是tableView是用这一行初始化的：
tableView = [[UITableView alloc] initWithFrame：CGRectMake（...）style：UITableViewStyleGrouped];
UPDATE 3
当我改变违规行如下，它工作正常。但我宁愿保持索引与它的表一样。
// SearchResult * result = [self.fetchedResultsController objectAtIndexPath：indexPath];
SearchResult * result = [[self.fetchedResultsController fetchedObjects] objectAtIndex：[indexPath indexAtPosition：1]]
对我来说，它有助于初始化 NSFetchedResultsController
cacheName：nil 。 I have a fetched result with a single section. I am able to access the objects using [[fetchedResultsController fetchedObjects] objectAtIndex:index] for all of the objects. But it is failing when I use objectAtIndexPath like this: [fetchedResultsController objectAtIndexpath:indexPath]
An error occurs after I insert an row (for one of the SearchResult objects) into the corresponding table. The object appears to be inserted into the new table correctly. After I have visually confirmed this, I select one of the rows, and then the fun begins.
Here is the code where the error is occurring:
- (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];
}
I am having a failure in the last line. The log looks like this:
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]
After executing the NSLog statements, I get an exception at the last line using [fetchedResultsController objectAtIndexPath:indexPath]. It happens for other index values too, but they always look valid.
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'no object at index 2 in section at index 0'
So, to summarize, there appear to be the right number of fetched objects, there is one section (0), I can access each one by one method, but not by the other. The indexPathForObject: is always returning (null).
Is this a bug or am I misunderstanding something?
UPDATE
Here is the code, implementing the NSFetchedResultsControllerDelegate protocol methods.
- (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
I don't know if it matters, but the tableView is initialized with this line:
tableView = [[UITableView alloc] initWithFrame:CGRectMake(...) style:UITableViewStyleGrouped];
UPDATE 3
When I change the offending line as follows, it works fine. But I would rather keep the indexing the same as it is with the table.
//SearchResult *result = [self.fetchedResultsController objectAtIndexPath:indexPath];
SearchResult *result = [[self.fetchedResultsController fetchedObjects] objectAtIndex:[indexPath indexAtPosition:1]]
I had the same problem now.
For me it helped to initialise NSFetchedResultsController with cacheName: nil.
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