Swift set or update asset in core data

Question

• Two Entities
• Gymnast is one to many to Meet
• I would like to when I save a new meet, it gets assigned to as a meet to each gymnast where they can then score their individuals scores for each event

Maybe I completely wrong in my logic, but here is what I am trying to do

let request = NSFetchRequest(entityName: "Gymnast")

    do {

        let entities = try AD.managedObjectContext.executeFetchRequest(request) as! [Gymnast]

        for item in entities {

            if let first = item.valueForKey("firstName"), last = item.valueForKey("lastName") {

                print("Name: \(first) \(last)")

                let myMeet = NSEntityDescription.insertNewObjectForEntityForName("Meet", inManagedObjectContext: AD.managedObjectContext) as! Meet

                myMeet.meetName = "Winter Classic"

                let myMeets = item.meets!.mutableCopy() as! NSMutableSet
                myMeets.addObject(myMeet)

                item.meets = myMeets.copy() as? NSSet

                AD.saveContext()

            }

        }

    } catch {

    }
}

}

Answer 1

I think it is not ideal to replicate the Meet object over and over again for each Gymnast. For example, the meetName will be stored multiple times. I am not sure this is intended.

However, going with your setup, your problem is how you assign the to-many relationship. For a one-to-many it is always easier to simply set the to-one relationship. (Remember, there is always a reverse relationship in the Core Data model.)

Thus,

myMeet.gymnast = item

is all you need.

To add and remove to-many relationships, you can use this extension:

// Support adding to many-to-many relationships

extension NSManagedObject {
    func addObject(value: NSManagedObject, forKey key: String) {
        let items = self.mutableSetValueForKey(key)
        items.addObject(value)
    }

    func removeObject(value: NSManagedObject, forKey key: String) {
        let items = self.mutableSetValueForKey(key)
        items.removeObject(value)
    }
}