Question

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSManagedObjectContext *context = [self managedObjectContext];

    if (editingStyle == UITableViewCellEditingStyleDelete) {
        NSLog(@"%@",context);
        // Delete object from database
        [context deleteObject:[self.devices objectAtIndex:indexPath.row]];
        NSLog(@"%@",context);

    NSError *error = nil;
    if (![context save:&error]) {enter code here
        NSLog(@"Can't Delete! %@ %@", error, [error localizedDescription]);
        return;
    }

    // Remove device from table view
    [self.devices removeObjectAtIndex:indexPath.row];
    [self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];


   }
}

错误是NSManagedObjectContext无法删除其他上下文中的对象

Answer 1

用于获取NSManagedObject的NSManagedObjectContext实例与当前实例不同。

另请检查：An NSManagedObjectContext cannot delete objects in other contexts

Answer 2

您必须使用与通过调用self.devices返回的NSManagedObjectContext不同的NSManagedObjectContext获取与[self managedObjectContext]关联的数组中的对象。您尝试删除的对象无法使用不同的上下文进行更改或操作，这就是您收到错误的原因。

你可以尝试做什么，如果要删除该对象，请将其拉出然后删除/更改对象，如下所示：

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSManagedObjectContext *context;

    if (editingStyle == UITableViewCellEditingStyleDelete) {
        NSLog(@"%@",context);
        // Delete object from database
        MyObject *object = [self.devices objectAtIndex:indexPath.row];
        context = object.managedObjectContext;
        [context deleteObject:object]
        NSLog(@"%@",context);

    NSError *error = nil;
    if (![context save:&error]) {enter code here
        NSLog(@"Can't Delete! %@ %@", error, [error localizedDescription]);
        return;
    }

    // Remove device from table view
    [self.devices removeObjectAtIndex:indexPath.row];
    [self.tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];


   }
}

这将适用于您的情况，但您应该如何使代码更容易使用NSFetchedResultsController。以下是一些有关如何使用它的有用链接：

http://www.raywenderlich.com/999/core-data-tutorial-for-ios-how-to-use-nsfetchedresultscontroller https://developer.apple.com/library/ios/documentation/CoreData/Reference/NSFetchedResultsController_Class/index.html

NSManagedObjectContext无法删除其他上下文中的对象

2 个答案: