How do you store an UInt64 in CoreData?

Question

My understanding is that a UInt64 can be any value from: 0 to 18446744073709551615

I need to save a UInt64 identifier to CoreData, however the values I see are:

I initially tried Integer 64 but now I am understanding that has a range of: -9223372036854775808 to 9223372036854775807

Do developers usually store an UInt64 as a String and do conversions between the two types? Is this the best practice?

Answer 1

The accepted answer by Martin R will work.

However it appears that this is part of the default implementation of @NSManaged properties by Apple.

I tested it like so:

1. I created a new Xcode project with Core Data and made a single Entity called Hello.
2. It has a single attribute called short which is saved as an Integer 16.
3. Marked Codegen as Manual/None
4. Created the manual class file for Hello as follows:

class Hello: NSManagedObject {
    @NSManaged var short : UInt16
}

You'll notice that I've typed it as an unsigned UInt16.

In my AppDelegate:

func applicationDidFinishLaunching(_ aNotification: Notification) {
        // Get Context
        let context = self.persistentContainer.viewContext

        // Create Test Objects
        let hello1 = Hello(entity: Hello.entity(), insertInto: context)
        hello1.short = 255
        let hello2 = Hello(entity: Hello.entity(), insertInto: context)
        hello2.short = 266 // Should overflow Int16
        let hello3 = Hello(entity: Hello.entity(), insertInto: context)
        hello3.short = 65535 // Should overflow Int16 by a lot

        // Save them to the database
        do {
            try context.save()
        } catch {
            print(error)
        }
        
        // Fetch the save objects
        let fetch = NSFetchRequest<Hello>(entityName: "Hello")
        if let results = try? context.fetch(fetch) {
            for result in results {
                print(result.short)
            }
        }
    }

This prints out the following:

255
266
65535

Which I imagine is what someone would want from saving unsigned ints in Core Data.