Question

I have a very strange error happening in an App that has been working for a long time.

I can no longer create one of my entities in my CoreData model.

When I create one particular entity in my model and try to print it using NSLog( @”%@”, obj ), I get this strange message:

2011-11-08 13:03:05.936 iLearnFast[31541:15503] -[__NSCFNumber objectID]: unrecognized selector sent to instance 0xa069e20

When I loop over the attributes / relationships for this object and print them out, one particular one to one relationship returns a strange value from [obj valueForKey:]. The value it returns is the same pointer / object that is mentioned in the above error message.

I thought I might have been corrupting memory somewhere, but I inserted the code to create the entity at the very beginning of my executable as soon as datastructures are initialized, and I get the same problem. I am extremely confident that I have not made any memory errors at this point (and a memory error would be more random … I can create thousands of objects, and always the same entity has the same problem with the same relationship, and no other entities ever have a problem).

After narrowing down the problem to this one relationship, I found that I could make the error go away by renaming the relationship to anything else. The relationship has been called “file” since my App was created.

I can make my code work again by renaming the property, although it messes up my automatic lightweight migration, but now I have to deal with figuring out how to do a more complicated migration.

If anyone has any ideas as to what might be going wrong, I would really appreciate it.

This is baffling me, and really feels like a bug in Apple’s SDK.

I’m currently using XCode 4.2 and tried both the SDKs for both iOS5.0 and iOS4.3 and both had the same behaviour.

Ron

Answer 1

2011-11-08 13:03:05.936 iLearnFast[31541:15503] -[__NSCFNumber
objectID]: unrecognized selector sent to instance 0xa069e20

I guess you have a leak in your code. This line means that you trying to access objectID property which contains in your custom NSManagedObject, but for some reason that object no longer lives. Try to check your code on memory leaks.