fetchedResultsContext並沒有真正刪除對象，並導致commitEditingStyle中的斷言問題

Question

我有一個奇怪的問題，需要一些幫助。

我在一個核心數據項目上，並沒有使用fetchedResultsController，只是使用fetchRequets和數組來填充zableviews。所以現在我決定改變和使用FRC ...

到目前爲止一切都非常簡單...但是與commitEditingStyle我從那時起就有問題 - 當刪除行時，我引發了一個像這樣的異常：

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. 

在我發現那是因爲我想刪除遺體在FRC ...對象我把一些NSLog的章節中的Liko這樣結尾：

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]; 

，結果是這樣的：

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 

當然，當我告訴tableview它會得到3行，但只能通過兩個...當然會嘔吐，但是這裏有什麼問題？

我的舊代碼是這樣看，沒有任何問題，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

它來到了RTFM ...所以我做了部分改變工作代碼如：

-(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，當我使用sectments在我的FRC我仍然得到同樣的錯誤......我找不到任何比這更多的是與FRC ...

有什麼想法？

Answer 1

1. 刪除
2. 檢查您是否已經正確實施FRC的委託方法後刪除了FRC的緩存。
3. 確保在運行FRC的委託方法之前凍結表格視圖beginUpdates。