核心数据-existingObjectWithID：错误：导致错误133000 [英] Core Data -existingObjectWithID:error: causes error 133000
问题描述
我的应用程序使用Core Data（使用Magical Record的一些帮助），并且使用 NSOperation 进行相当严重的多线程。
当然，我非常小心，只在线程/操作之间传递 NSManagedObjectID 。
回到操作中的相应托管对象，我使用 -existingObjectWithID：error：：
Collection * owner =（Collection *）[localContext existingObjectWithID：self.containerId error：& error];
但是我得到的是nil和错误说这是一个错误＃13300： NSManagedObjectReferentialIntegrityError 。
这里是文档说的这个错误： / p>
<$ c $ p> NSManagedObjectReferentialIntegrityError
表示尝试触发指向不存在的对象的故障的错误代码。
可访问存储，但找不到与故障相对应的对象。
在我的情况下不是真的：那个对象存在。事实上，如果我用 NSFetchRequest 遍历 Collection 实体的所有实例，我发现它在其中， NSManagedObjectID 正是我传递给 -existingObjectWithID：error：。
此外，如果我使用 -objectWithID：，我得到一个正确的对象，只是罚款。
所以有一些我错过了。以下是一些其他的意见/问题：
- 不存在的对象：句子？ 存在在哪里？
- 无法找到对应于故障的对象：该句子中found的含义是什么？ 发现在哪里？
所以也许我缺少一些关于 existingObjectWithID：error：是吗？文档说：
如果有上下文中已经注册了给定ID的托管对象，否则相应的对象被故障到上下文中。
[...]
与objectWithID：不同，此方法不会返回错误。
这对我的问题没有帮助。我不介意让我的对象完全故障，而不是故障。事实上，当我访问对象属性时，其中的任何错误都会在下一个代码行上触发。
-
NSManagedObjectReferentialIntegrityError？
感谢任何启发。
$问题是，你传递的 NSManagedObjectID 是临时的。您可以通过调用 NSManagedObjectID 的 isTemporaryID 方法来检查它。来自docs：
返回一个布尔值，表示
接收方是否是临时的。
大多数对象ID返回NO。新对象插入
被管对象上下文中被分配一个临时ID，一旦对象被保存到持久化存储中，它被替换为永久的一个临时ID。
您应该先将更改保存到持久存储，然后再获取永久ID以传递给其他上下文。
My app uses Core Data (with some help of Magical Record) and is rather heavily multithreaded using NSOperation.
Of course I am very careful to only pass around NSManagedObjectID between threads/operations.
Now, to get back to the corresponding managed object in an operation, I use -existingObjectWithID:error: thus:
Collection *owner = (Collection *)[localContext existingObjectWithID:self.containerId error:&error];
But what I get back is nil and error says this is an error #13300: NSManagedObjectReferentialIntegrityError.
Here is what the documentation says about this error:
NSManagedObjectReferentialIntegrityError
Error code to denote an attempt to fire a fault pointing to an object that does not exist.
The store is accessible, but the object corresponding to the fault cannot be found.
Which is not true in my case: that object exists. Indeed, If I iterate through all instances of that Collection entity with an NSFetchRequest, I find it among them, and its NSManagedObjectID is exactly the one I passed to -existingObjectWithID:error:.
Moreover, if I use -objectWithID: instead, I get a correct object back just fine.
So there is something I'm missing. Here are a few additional observations/questions:
- "an object that does not exist": what it the meaning of "exist" in that sentence? "exist" where? It definitely "exists" in my Core Data store at that point.
- "the object corresponding to the fault cannot be found": what it the meaning of "found" in that sentence? "found" where? It definitely "be found" in my Core Data store at that point.
So maybe I am missing something regarding what existingObjectWithID:error: does? The documentation says:
If there is a managed object with the given ID already registered in the context, that object is returned directly; otherwise the corresponding object is faulted into the context.
[...]
Unlike objectWithID:, this method never returns a fault.
This doesn't help my issue. I don't mind getting my object fully faulted, and not a fault. In fact, any fault within it will fire on the next code line when I access the object properties.
- What would be a realistic scenario leading to an
NSManagedObjectReferentialIntegrityError?
Thanks for any enlightenment.
The problem is that NSManagedObjectID you pass is temporary. You can check it by calling NSManagedObjectID's isTemporaryID method. From docs:
Returns a Boolean value that indicates whether the receiver is temporary.
Most object IDs return NO. New objects inserted into a managed object context are assigned a temporary ID which is replaced with a permanent one once the object gets saved to a persistent store.
You should first save your changes to persistent store, only then get a permanent ID to pass to other context.
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