Swift 5 NSFetchRequest predicate when trying to lookup a String UUID-CodePudding

I have a string UUID coming into this method, to lookup an entity in CoreData that has UUID's saved as UUID type (Not String).

I keep getting "Fatal error: Unexpectedly found nil while unwrapping an Optional value" on line for the predicate.

func loadUser(uuid: String) -> [ExistingUsers2] {
    let request : NSFetchRequest<ExistingUsers2> = ExistingUsers2.fetchRequest()
    let uuidQuery = NSUUID(uuidString: uuid)
    request.predicate = NSPredicate(format: "%K == %@", #keyPath(ExistingUsers2.uuid), uuidQuery! as CVarArg)
    request.sortDescriptors = [NSSortDescriptor(key: "name", ascending: true)]
    do {
        existingUsersArray = try context.fetch(request)
        print("Returned \(existingUsersArray.count)")
    } catch {
        print("Error fetching data from context \(error)")
    }
    return existingUsersArray
}

Any help? I haven't found anything here or Dr Google. TKS

CodePudding user response：

Try this as your predicate: NSPredicate(format: "cid = %@", "\(id)")

where cid is the UUID in CoreData and id is the UUID you got from the string. Also do not use NSUUID.

CodePudding user response：

You can replace your predicate with this:

guard let uuidQuery = UUID(uuidString: uuid) else { return [] } // no valid UUID with this code
request.predicate = NSPredicate(format: "%K == %@", #keyPath(ExistingUsers2.uuid), uuidQuery as CVarArg)

Everything else should work.

CodePudding user response：

Replace the uuidAttributeName with your attribute name and yourStringuuid with the your string that you want to convert into UUID type.

var uuid = UUID(uuidString: yourStringuuid)

let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "ExistingUsers2")
fetchRequest.predicate = NSPredicate(format: "uuidAttributeName == %@",uuid)

let results = try context.fetch(fetchRequest)