CoreData - 多个持久存储 [英] CoreData - multiple persistent stores

问题描述

我需要一些帮助理解CoreData。

I need some help understanding CoreData.

假设我安装了MagicalRecords和RestKit，我也有一个服务器，它可以返回一些帖子 。然后，我需要保存一些帖子到设备内存，所以用户可以稍后阅读该帖子（即使没有互联网连接）。为了不浪费内存，很明显，我应该使用内存存储，我这样做。但是为了保存帖子我definitley想要SQLite或某物，它使我真的无奈。

Let's say I have MagicalRecords and RestKit installed, and I also have a server, which can return me some posts. Then I need to save some of those posts onto device memory, so a user can read the post later on (even with no internet connection). To not rubbish the memory, it's obvious that I should use in-memory storage, which I do. But for saving the posts I definitley want SQLite or something, and it makes me really helpless.

问题是，苹果没有给出很多关于如何处理这种排序的信息的情境，和谷歌没有帮助到目前为止。我猜我必须做两个永久存储和两个配置：默认和保存一个。我找到了一种方法来创建两个永久性存储，但现在我只是不明白如何使用：如何创建和保存在确切存储我想要的，如何传输它们在商店之间，这将如何与RK和MR进行交互？

任何帮助将被淹没。链接，信息，代码段

The problem is, Apple do not give much information about how to handle this sort of situatuion, and the googling did not help so far. I'm guessing that I have to make two persistent stores and two configurations: the default and the "saving" ones. I have found a way to make two persistent stores, but now I just don't understand how to work with that: how to create and save enteties in exact store I want, how to transfer them between stores, how will this interact with RK and MR?
Any help will be aprichiated. Links, info, code snippets

推荐答案

一般来说，

使用不同的命名配置设置数据模型。每个配置定义包含一个或多个实体的模型的子集。您可以在模型编辑器中执行此操作。当通过调用 addPersistentStoreWithType：configuration：URL：options：error：添加持久存储时，为第二个参数提供配置名称。

Set up your data model with different named configurations. Each configuration defines a subset of the model that contains one or more of the entities. You do this in the model editor. When you add a persistent store by calling addPersistentStoreWithType:configuration:URL:options:error:, provide a configuration name for the second argument. Any time you insert a new instance, it will go to the correct persistent store, based on the configuration.

不要打扰配置。相反，在插入新实例后，使用 NSManagedObjectContext 的方法 assignObject：toPersistentStore：

Don't bother with configurations. Instead, after you insert a new instance, use NSManagedObjectContext's method assignObject:toPersistentStore: to tell it which persistent store file to use.

完全由您自己决定。没有直接的框架支持。您不能使用 assignObject：toPersistentStore：将实例重新分配给不同的存储文件。您必须在不同的存储区中创建一个新实例，并自己复制所有属性值和关系。

It's all up to you. There is no direct framework support. You cannot use assignObject:toPersistentStore: to reassign an instance to a different store file. You would have to create a new instance in a different store and copy over all attribute values and relationships yourself.

我不知道MagicalRecord或RestKit如何支持这个，他们甚至做。

I have no idea how MagicalRecord or RestKit support this, or if they even do.

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