核心数据：错误，“不能合并具有两个不同实体的模型命名为'foo'”

问题描述

我正在使用一个使用Core Data的iPhone应用程式。大多数时候，我只是在模拟器测试，但偶尔将应用程序下载到iPad以确保。

I'm working on an iPhone app that uses Core Data. Most times, I just test in the simulator, but occasionally pump the app down to the iPad to make sure.

我最近更改了我的Core Data模型，现在当我把应用程序发送到iPad，我得到一个SIGABRT异常告诉我：

I've recently changed my Core Data model, and now when I send the app to the iPad, I get a SIGABRT exception telling me:

 Can't merge models with two different entities named 'foo'

好的，我明白了。设备上存在旧版本的数据库。所以，我（尝试）通过按/应用程序的图标杀死旧版本，直到它开始摆动，然后点击其X。 iPad会问我是否要删除应用程序及其所有数据。我说是的。

OK, that I understand. Old version of the database exists on the device. So, I (try to) kill the old version by press/holding the application's icon until it starts wiggling, and then tap its "X". The iPad asks me if I want to delete the application and all of its data. I say yes.

我重建应用程序，定位到iPad，并得到相同的错误。

I rebuild the app, targetting the iPad, and get the same error.

有没有让老数据库真正走开的窍门？

Is there a trick to getting the old database to really go away?

推荐答案

对于那些在尝试使用core数据轻量级迁移：

For those who come across this question after trying to use core data lightweight migrations:

即使遵循了创建新版本数据模型的说明，我也遇到了此问题。我注意到，在我的应用程序包中有两个.mom文件，一个.mom和一个包含.mom文件的.momd目录。

I was having this issue even after following the instructions for creating a new version of my data model. I noticed that there were two ".mom" files in my application bundle, one ".mom" and one ".momd" directory that contained ".mom" files.

根据这一点，我能够找到解释问题并提供解决方案。

Based on that, I was able to find this excellent post explaining the issue and offering a solution.

关键是替换为此实现生成的 - （NSManagedObjectModel *）managedObjectModel 的实现：

The key is to replace the implementation of - (NSManagedObjectModel *)managedObjectModel that is generated for you with this implementation:

- (NSManagedObjectModel *)managedObjectModel {

    if (managedObjectModel != nil) {
        return managedObjectModel;
    }

    NSString *path = [[NSBundle mainBundle] pathForResource:@"Foo" ofType:@"momd"];
    NSURL *momURL = [NSURL fileURLWithPath:path];
    managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:momURL];

    return managedObjectModel; }

其中Foo是您的数据模型的名称。

where 'Foo' is the name of your data model.

希望这对某人有用 - 我花了太多的时间在我的头撞墙。再次感谢，苹果！ ：）

Hopefully this is useful to someone - I spent WAY too many hours beating my head against the wall on this. Thanks again, Apple! :)

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