Core Data exception: [__NSCFString objectID]: unrecognized selector sent to instance

Question

Created Oct ’20

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I am loading JSON in background thread and saving it in Core Data. 99.9% of times everything works, but occasionally I get a strange background crash, with this exception:

Code Block -[NSCFString objectID]: unrecognized selector sent to instance 0x7b14001efcd0
(
	0   CoreFoundation                      0x00007fff2043a126 exceptionPreprocess + 242
	1   libobjc.A.dylib                     0x00007fff20177f78 objc_exception_throw + 48
	2   CoreFoundation                      0x00007fff20448c6f +[NSObject(NSObject) instanceMethodSignatureForSelector:] + 0
	3   CoreFoundation                      0x00007fff2043e666 _forwarding_ + 1489
	4   CoreFoundation                      0x00007fff20440698 _CF_forwarding_prep_0 + 120
	5   CoreData                            0x00007fff251a034b -[NSManagedObjectContext _disposeObjects:count:notifyParent:] + 176
	6   CoreData                            0x00007fff25195b20 -[NSManagedObjectContext _dispose:] + 297
	7   CoreData                            0x00007fff2510f004 -[NSManagedObjectContext _dealloc] + 570
	8   CoreData                            0x00007fff251ac1be internalBlockToDeallocNSManagedObjectContext_block_invoke + 43
	9   CoreData                            0x00007fff25109933 developerSubmittedBlockToNSManagedObjectContextPerform + 154
	10  libclang_rt.tsan_iossim_dynamic.dyl 0x00000001098f2c72 _ZN6__tsanL22dispatch_callback_wrapEPv + 306
	11  libdispatch.dylib                   0x00007fff20106534 _dispatch_client_callout + 8
	12  libdispatch.dylib                   0x00007fff2010c425 _dispatch_lane_serial_drain + 715
	13  libdispatch.dylib                   0x00007fff2010cfa0 _dispatch_lane_invoke + 403
	14  libdispatch.dylib                   0x00007fff20117591 _dispatch_workloop_worker_thread + 782
	15  libsystem_pthread.dylib             0x00007fff5dcd8a3d _pthread_wqthread + 290
	16  libsystem_pthread.dylib             0x00007fff5dcd7b77 start_wqthread + 15
)

Object 0x7b14001efcd0 which is being asked for objectID it really is a string, it's actually the NSManagedObjectID:

Code Block (lldb) po 0x7b14001efcd0
x-coredata://EA951A1D-C5F1-4CAA-80DA-D187C94817D4/Event/p101

Is this maybe a bug in Core Data or is there something I can do to fix this? Not a single line in my code is present in thread stack list.

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Answer 1

bernardkroes OP

Nov ’20

I am having the exact same issue reported in a crash log.
I am, so far, unable to reproduce this myself.
Did you have any luck fixing this crash somehow, or finding a (probable) cause, aleck?

0

Answer 2

Engineer OP

Apple

Dec ’20

com.apple.CoreData.ConcurrencyDebug 1

is your friend. If that doesn't help, I'd next try ASAN and NSZombies (not at the same time)

here you have an object that used to be an NSManagedObject, but it's been over released, and replaced in the same pointer address with an NSString.

0