Question

当我使用以下代码从TableView中删除一行时：

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete the row from the data source

        NSError *error = nil;
        NSLog(@"Rows before deletion: %d", [[self.fetchedResultsController fetchedObjects] count]);
        NSManagedObject *obj = [self.fetchedResultsController objectAtIndexPath:indexPath];
        [self.managedContext deleteObject:obj];
        NSLog(@"Rows before save: %d", [[self.fetchedResultsController fetchedObjects] count]);
        if (![self.managedContext save:&error]) {
            NSLog(@"Error while deleting time: %s", error.localizedDescription);
        }
        NSLog(@"Rows after save: %d", [[self.fetchedResultsController fetchedObjects] count]);
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];


    }   
    else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
    }   
}

然后我得到以下错误。可能是什么原因？对象的数量每次都是相同的。为什么上下文不会获取已删除对象的此信息。不是自动的吗？

错误是删除行后的行数必须是删除/添加的行的加号或减号。

由于

Answer 1

保存上下文后，您必须重新执行“更新”self.fetchedResultsController的请求。

if (![self.managedContext save:&error]) {
        NSLog(@"Error while deleting time: %s", error.localizedDescription);
    }
self.fetchedResultsController = ...    
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
...

从ManagedContext中删除对象并从TableView中删除单元格后出错

1 个答案: