CORE DATA objectId changes constantly
original source : https://stackoverflow.com/questions/2819242/core-data-objectid-changes-constantly
core data에서 자체 만들어지는 NSManagedObjectID는 수시로 바뀔수 있음으로 이를 특정 데이터를 접근하기 위한 고유 id로 사용해서는 안된다.
NSManagedObjectID is not guaranteed to be consistent. It can change based on a number of factors including data migration and other factors. If you are using this as a unique identifier for your objects, stop.
The only time you want to use the
NSManagedObjectID is when you need to pass references between threads. Other than that situation you should not rely upon it for anything.
If you need a unique id then create one and store it in your entities.