fetchedResultsContext并没有真正删除对象，并导致commitEditingStyle中的断言问题

Question

我有一个奇怪的问题，需要一些帮助。

我在一个核心数据项目上，并没有使用fetchedResultsController，只是使用fetchRequets和数组来填充zableviews。所以现在我决定改变和使用FRC ...

到目前为止一切都非常简单...但是与commitEditingStyle我从那时起就有问题 - 当删除行时，我引发了一个像这样的异常：

The number of rows contained in an existing section after the update (1) must be equal to the number of rows contained in that section before the update. 

在我发现那是因为我想删除遗体在FRC ...对象我把一些NSLog的章节中的Liko这样结尾：

NSLog(@"Number before deleting: %i - deleting %@",[[fetchedResultsController fetchedObjects] count], [fetchedResultsController objectAtIndexPath:indexPath]); 

    NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; 
    [context deleteObject:[fetchedResultsController objectAtIndexPath:indexPath]]; 

    NSLog(@"Number before saving: %i",[[fetchedResultsController fetchedObjects] count]); 

    NSError *error; 
    if (![context save:&error]) { 

     [NSException raise:NSGenericException format:@"Following error occured when trying to delete %@: %@", [fetchedResultsController objectAtIndexPath:indexPath], [error description]]; 
    } 

    NSLog(@"Number after saving: %i",[[fetchedResultsController fetchedObjects] count]); 

    NSArray * cellsToDelete = [NSArray arrayWithObject:indexPath]; 
    [tableView deleteRowsAtIndexPaths:cellsToDelete withRowAnimation:UITableViewRowAnimationFade]; 

，结果是这样的：

2011-05-20 14:49:35.398 Nivellator[6000:207] Number before deleting: 3 
2011-05-20 14:49:35.399 Nivellator[6000:207] Number before saving: 3 
2011-05-20 14:49:35.404 Nivellator[6000:207] Number after saving: 3 

当然，当我告诉tableview它会得到3行，但只能通过两个...当然会呕吐，但是这里有什么问题？

我的旧代码是这样看，没有任何问题，工作...

-(void) tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath 
{ 
    if ([tableView isEqual:self.entityTableView] == YES) { 
     if (editingStyle != UITableViewCellEditingStyleDelete) { 
      return; 
     } 

     if ([self.entityArray count] <= indexPath.row) { 
      return; 
     } 

     Member *thisEntity = [self.entityArray objectAtIndex:indexPath.row]; 
     [delegate.managedObjectContext deleteObject:thisEntity]; 

     NSError *savingError = nil; 

     if ([delegate.managedObjectContext save:&savingError] == YES) { 

      // Remove the entity from the Array and delete the corresponding table cell with animation 
      // 
      [self.entityArray removeObject:thisEntity]; 

      NSArray * cellsToDelete = [NSArray arrayWithObject:indexPath]; 
      [tableView deleteRowsAtIndexPaths:cellsToDelete withRowAnimation:UITableViewRowAnimationFade]; 
     } else { 
      /* Error handling missing */ 
     } 
    } 
} 

OK

到底

它来到了RTFM ...所以我做了部分改变工作代码如：

-(void) tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath 
{ 
    if ([tableView isEqual:self.entityTableView] == YES) { 
     if (editingStyle != UITableViewCellEditingStyleDelete) { 
      return; 
     } 

     NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; 
     [context deleteObject:[fetchedResultsController objectAtIndexPath:indexPath]]; 

     NSError *error; 
     if (![context save:&error]) { 

      [NSException raise:NSGenericException format:@"Following error occured when trying to delete %@: %@", [fetchedResultsController objectAtIndexPath:indexPath], [error description]]; 
     } 

     if ([fetchedResultsController performFetch:&error]) { 

      [tableView beginUpdates]; 

      NSArray * cellsToDelete = [NSArray arrayWithObject:indexPath]; 
      [tableView deleteRowsAtIndexPaths:cellsToDelete withRowAnimation:UITableViewRowAnimationFade]; 

      [tableView endUpdates]; 
     } else { 

      [NSException raise:NSGenericException format:@"Following error occured when trying to delete %@: %@", [fetchedResultsController objectAtIndexPath:indexPath], [error description]]; 
     } 
    } 
} 

但是，当我使用sectments在我的FRC我仍然得到同样的错误......我找不到任何比这更多的是与FRC ...

有什么想法？

Answer 1

1. 删除
2. 检查您是否已经正确实施FRC的委托方法后删除了FRC的缓存。
3. 确保在运行FRC的委托方法之前冻结表格视图beginUpdates。