Swift and CoreData, problems with relationship (NSSet) - [NSSet intersectsSet:]: set argument is not an NSSet

Question

I've been trying to get my head around adding objects in relationships using CoreData and Swift. I am at a loss, I do not understand why my code does not work. I am trying to add an "Event" to a "Team". I can not find the difference between accepted answers (that should work), and my code (that does not).

Teams.swift:

import Foundation
import CoreData

class Teams: NSManagedObject {

    @NSManaged var teamName: String
    @NSManaged var matches: NSSet

}

extension Teams {

    func addEventToTeam(event:Event) {
        //self.mutableSetValueForKeyPath("matches").addObject(event)

        var matchez: NSMutableSet

        matchez = self.mutableSetValueForKey("matches")
        matchez.addObject(event)


        //var manyRelation = self.valueForKeyPath("matches") as NSMutableSet
        //manyRelation.addObject(event)
    }

    func getTeamName() -> String {
        return teamName
    }


}

Calling code (from configure view):

import UIKit
import CoreData

class DetailViewController: UIViewController, NSFetchedResultsControllerDelegate {

    var managedObjectContext: NSManagedObjectContext? = nil

    @IBOutlet weak var detailDescriptionLabel: UILabel!


    var detailItem: AnyObject? {
        didSet {
            // Update the view.
            self.configureView()
        }
    }

    func configureView() {
        // Update the user interface for the detail item.
        if let detail: Event = (self.detailItem as? Event) {
        //if let detail: AnyObject = self.detailItem {

            if let label = self.detailDescriptionLabel {
                label.text = detail.valueForKey("timeStamp").description

                self.insertNewObject(self);
                label.text = String(detail.getNumberOfTeams())

                //detail.getTeams().
                var hej: Array<Teams>
                hej = detail.getTeams()

                label.text = "tjosan"

                for tmpTeam : Teams in hej {
                    label.text = label.text + ", " + tmpTeam.getTeamName()
                }


            }
        }

        if true {


        }


    }

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        self.configureView()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    var fetchedResultsController: NSFetchedResultsController {
        if _fetchedResultsController != nil {
            return _fetchedResultsController!
            }

            let fetchRequest = NSFetchRequest()
            // Edit the entity name as appropriate.
            let team = NSEntityDescription.entityForName("Teams", inManagedObjectContext: self.managedObjectContext)
            fetchRequest.entity = team

            // Set the batch size to a suitable number.
            fetchRequest.fetchBatchSize = 20

            // Edit the sort key as appropriate.
            let sortDescriptor = NSSortDescriptor(key: "teamName", ascending: false)
            let sortDescriptors = [sortDescriptor]

            fetchRequest.sortDescriptors = [sortDescriptor]

            // Edit the section name key path and cache name if appropriate.
            // nil for section name key path means "no sections".
            let aFetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.managedObjectContext, sectionNameKeyPath: nil, cacheName: "Master")
            aFetchedResultsController.delegate = self
            _fetchedResultsController = aFetchedResultsController

            var error: NSError? = nil
            if !_fetchedResultsController!.performFetch(&error) {
                // Replace this implementation with code to handle the error appropriately.
                // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
                //println("Unresolved error \(error), \(error.userInfo)")
                abort()
            }

            return _fetchedResultsController!
    }    
    var _fetchedResultsController: NSFetchedResultsController? = nil



    func insertNewObject(sender: AnyObject) {
        let context = self.fetchedResultsController.managedObjectContext
        let team = self.fetchedResultsController.fetchRequest.entity
        let newManagedObject = NSEntityDescription.insertNewObjectForEntityForName(team.name, inManagedObjectContext: context) as Teams

        // If appropriate, configure the new managed object.
        // Normally you should use accessor methods, but using KVC here avoids the need to add a custom class to the template.
        newManagedObject.setValue("Lagur Namnurk", forKey: "teamName")

        newManagedObject.addEventToTeam(self.detailItem as Event)


        // Save the context.
        var error: NSError? = nil
        if !context.save(&error) {
            // Replace this implementation with code to handle the error appropriately.
            // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            //println("Unresolved error \(error), \(error.userInfo)")
            abort()
        }
    }



}

Error message:

2014-08-13 18:38:46.651 Score Calculator 2[10538:829319] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSSet intersectsSet:]: set argument is not an NSSet'
*** First throw call stack:
(
    0   CoreFoundation                      0x00000001028a53e5 __exceptionPreprocess + 165
    1   libobjc.A.dylib                     0x00000001043b8967 objc_exception_throw + 45
    2   CoreFoundation                      0x000000010280fc6c -[NSSet intersectsSet:] + 940
    3   Foundation                          0x0000000102d0c4a6 NSKeyValueWillChangeBySetMutation + 156
    4   Foundation                          0x0000000102c804fa NSKeyValueWillChange + 386
    5   Foundation                          0x0000000102d0c3fb -[NSObject(NSKeyValueObserverNotification) willChangeValueForKey:withSetMutation:usingObjects:] + 310
    6   CoreData                            0x00000001024178d7 -[NSManagedObject(_NSInternalMethods) _includeObject:intoPropertyWithKey:andIndex:] + 551
    7   CoreData                            0x0000000102418294 -[NSManagedObject(_NSInternalMethods) _maintainInverseRelationship:forProperty:forChange:onSet:] + 276
    8   CoreData                            0x0000000102416ef2 -[NSManagedObject(_NSInternalMethods) _didChangeValue:forRelationship:named:withInverse:] + 562
    9   Foundation                          0x0000000102c835d6 NSKeyValueNotifyObserver + 356
    10  Foundation                          0x0000000102c827fd NSKeyValueDidChange + 466
    11  Foundation                          0x0000000102d0c7ee -[NSObject(NSKeyValueObserverNotification) didChangeValueForKey:withSetMutation:usingObjects:] + 118
    12  CoreData                            0x00000001024180b0 -[NSManagedObject didChangeValueForKey:withSetMutation:usingObjects:] + 80
    13  CoreData                            0x000000010242fa11 -[_NSNotifyingWrapperMutableSet addObject:] + 161

edit: a couple of clarifications. Teams and Event have a multi-to-multi, unordered relationship.

Answer 1

Yesss!! I found the answer!

I had created a new function in the class Events.swift (the other side of the relationship).

I had written the following code:

import Foundation
import CoreData

class Event: NSManagedObject {

    @NSManaged var timeStamp: NSDate
    @NSManaged var teams: NSSet

}

extension Event {

    func addTeamToEvent(team:Teams) {
        var teamz = self.mutableSetValueForKey("teams")
        teamz.addObject(team)
    }

    func getNumberOfTeams() -> Int {
        return self.teams.count;
    }

    func getTeams() -> [Teams] {
        var tmpsak: [Teams]
        tmpsak = self.teams.allObjects as [Teams]
        tmpsak = self.teams.allObjects as [Teams]

        return tmpsak
    }

}

which I thought was unrelated. However, renaming getTeams to getTeamsAsArray removed the problem. I am guessing that CoreData, when filling in the other end of the relationship, uses a built-in function called getTeams() (since the other class was called Teams). I accidentally overrode(?) it, causing it to fail.

Thank you for your suggestions, and I hope this can be helpful to someone else!

On a somewhat related note, a bug with similar symptoms was identified a few years ago (and appears to still be present), that shows itself in auto-generated code when using ordered many-to-many relationships.

Answer 2

If you use the objective C generated NSManagedObject subclasses, they include custom methods for adding a single object - I think these are tried and tested and seem better than what is currently there for swift.

Theoretically you would just need to just set the new set with whatever new set you created. One option would be:

    var matchobjs = matches.allObjects as [Event]
    matchobjs.append(event)
    matches = NSSet(array: matchobjs)

However the error looks very similar to this post:

Which to me looks like theres something fishy going on again with many-to-many relationships...