Question

What is the best way to handle temporary objects in Core Data? I’ve seen solutions where temporary contexts are created, where they are inserted into nil contexts, etc.

However, here’s the issue I’m seeing in both of these solutions. I’m using Core Data for my object model and and in some of my views store a NSSet of Core Data objects. The problem I have is when the object is stored, the objectID changes which effectively invalidates anything stored in any NSSet since the isEqual and hash are now different. While I could invalidate the object stored in the NSSet, it often is not practical and certainly not always easy.

Here’s the things I’ve considered:

1) override isEqual method and hash on NSManagedObject (obviously bad)

2) do not place any NSManagedObject in a NSSet (use a NSDictionary where the key is always fixed)

3) use an entirely different type to store in NSSet where I could correctly implement the isEqual and hash code methods

Does anyone have a better solution for this?

Answer 1

However, here’s the issue I’m seeing in both of these solutions. I’m using Core Data for my object model and and in some of my views store a NSSet of Core Data objects. The problem I have is when the object is stored, the objectID changes which effectively invalidates anything stored in any NSSet since the isEqual and hash are now different.

tjg184,

Your problem here is not the transition to permanent IDs but that your container class depends upon an immutable hash. Hence, change your container class to an array or dictionary and this problem goes away. (You give up uniquing with an array but that is easy to handle with a trip through a transient set to perform the uniquing.)

Andrew