iOS18 Crash FetchedProperty CoreData

Yeah, Core Data fetched property is broken in iOS 18, and the team is actively working on that. The error message I saw was pretty much the same as what you provided, but I’d still suggest that you file your own feedback report so your use case is covered by the potential fix – If you do so, please share your report ID here for folks to track.

Best,
——
Ziqiao Chen
 Worldwide Developer Relations.

Hello,

Is there any new about this? We are experiencing the same issue.

I need a solution, how do you fix this?

Also having this problem, 18.1 and up seems to work without any code changes, but app crashing on 18.0 consistently. Is there a workaround for fetched properties on 18 so I can put a fix out for older versions of iOS/iPad OS?

The bug is real, even the official Apple's guide Linking Data Between Two Core Data Stores crashes on launch on iOS 18.0.

It would help if Apple Engineers could have a look at this solution:

How about manually fetching the corresponding records from Core Data? In the Apple's example, instead of

extension Book {
    var feedbackList: [Feedback]? { // The accessor of the feedbackList property.
        return value(forKey: "feedbackList") as? [Feedback]
    }
}

have something like:

import CoreData

extension Book {
    var feedbackList: [Feedback]? { // The accessor of the feedbackList property.
        if #available(iOS 18.1, *) {
            //iOS 18.1+ usual code (current)
            return value(forKey: "feedbackList") as? [Feedback]
        } else if #available(iOS 18, *) {
            //iOS 18.0-18.1 only code
            return fetchFeedbackManually()
        } else {
            //below iOS 18.0 usual code
            return value(forKey: "feedbackList") as? [Feedback]
        }
    }
    
    private func fetchFeedbackManually() -> [Feedback]? {
        guard let viewContext = self.managedObjectContext,
              let bookUUID = self.uuid else {
            return nil
        }
        
        return viewContext.performAndWait {
            let request: NSFetchRequest<Feedback> = Feedback.fetchRequest()
            request.predicate = NSPredicate(format: "bookUUID == %@", bookUUID as CVarArg)
            
            do {
                return try viewContext.fetch(request)
            } catch {
                return nil
            }
        }
    }
}

It seems to work, but I can't say what the consequences of such an approach are...