来自临时 URI 的永久 NSManagedObject URI？
我有一个 NSManagedObject 子类，它存储子对象的 URI。它最初会在子对象首次创建时存储临时 URI，并在保存之前实现 -willSave 在其 NSManagedObjectContext 上调用 -obtainPermanentIDsForObjects，以便仅保留永久 ID 。
不过，我遇到的问题是其他实例也存储临时 URI。当一个对象在具有相同子对象的另一个对象收到 -willSave 消息后不久收到时，它也会调用 -obtainPermanentIDsForObjects 并得到一个不同的、错误 永久 URI，导致后续的核心数据故障错误，例如：
CoreData 无法满足 '0x102e4c110
我想要一种从 NSManagedObject 的旧的、临时的 URIRepresentation 到已生成的新的、永久的 URIRepresentation 的方法。
我最初的想法是存储我自己的 -obtainPermanentIDsForObjects 之前进行查找 - 是否有更简单的（更简单或更简单的）内置）我缺少的方式？我在文档中没有发现任何暗示。
I have an NSManagedObject subclass which stores URIs of child objects. It initially stores the temporary URI when a child object is first created, and implements -willSave to call -obtainPermanentIDsForObjects on its NSManagedObjectContext before saving, so that only the permanent ID is persisted.
The problem I'm running into, though, is that other instances also store the temporary URI. When one gets the -willSave message shortly after another object with the same child does, it also calls -obtainPermanentIDsForObjects and gets a different, wrong permanent URI, causing subsequent Core Data fault errors like:
CoreData could not fulfill a fault for '0x102e4c110 <x-coredata://E17EE19B-E7F3-4102-ACFF-3E6F8BE8B104/MyEntityName/p2>'
I would like a way to get from an NSManagedObject's old, temporary, URIRepresentation to its new, permanent, URIRepresentation that was already generated.
My initial thought is to store my own dictionary of <temporary URI,permanent URI> and look up against that before using -obtainPermanentIDsForObjects - is there an easier (more foolproof or built-in) way that I'm missing? Nothing I found in the documentation suggested anything.
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我最终在创建子对象后（在它属于任何父对象之前）立即通过
-obtainPermanentIDsForObjects调用获得了永久 ID。这样，父对象就永远不会看到临时 ID。这是可行的，尽管我仍然渴望听到是否有更好的解决方案。I ended up getting a permanent ID with the
-obtainPermanentIDsForObjectscall immediately after creating the child object, before it belongs to any parent. That way, the parent object never sees a temporary ID. This works, though I'm still anxious to hear if there are any better solutions.订阅托管对象上下文的
NSManagedObjectContextDidSaveNotification。遍历 NSInsertedObjectsKey 中的对象并获取它们的托管对象 ID。此时，它们都将是正确的、永久的 ID，您可以安全地获取 URI 并存储它。Subscribe to your managed object context's
NSManagedObjectContextDidSaveNotification. Iterate through the objects in theNSInsertedObjectsKeyand get their managed object ids. At this point, they will all be the correct, permanent id and you can safely get the URI and store it.