CODEWITHSUNDEEP
iosswiftcore-data
Jonny
Jonny

Reputation: 67

How to correctly map one-to-many relationship using core data in Swift? Getting NSInvalidArgumentException error during attempts

Here's my medicine object class and extension:

import Foundation
import CoreData

class Medicine: NSManagedObject {

    @NSManaged var alarms: NSSet

}

-

import Foundation
import CoreData

extension Medicine {

@NSManaged var name: String?
@NSManaged var dosage: String?
@NSManaged var type: String?
@NSManaged var image: NSData?

func addAlarmObject(value:Alarm) {
    let items = self.mutableSetValueForKey("alarms") 
    items.addObject(value)
}

func removeDeleteObject(value:Alarm) {
    let items = self.mutableSetValueForKey("alarms")
    items.removeObject(value)
}

}

My alarm object:

import Foundation
import CoreData

extension Alarm {

    @NSManaged var time: String?
    @NSManaged var weekdays: String?
    @NSManaged var isOwnedByMedicine: Medicine?

}

Screenshot of my data models and their relationship:

enter image description here

FINALLY, here is what I'm trying to do:

        let predicate = NSPredicate(format: "name == %@", currentMedicine)
        let fetchRequest = NSFetchRequest(entityName: "Medicine")
        fetchRequest.predicate = predicate
        var fetchedCurrentMedicine:Medicine!
        do {
            let fetchedMedicines = try managedContext.executeFetchRequest(fetchRequest) as! [Medicine]
            fetchedCurrentMedicine = fetchedMedicines.first
        } catch {

        }

        //add all the alarms to the Medicine class
        for alarmString in alarmList{
            let entity =  NSEntityDescription.entityForName("Alarm", inManagedObjectContext: managedContext)
            let alarm = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedContext) as! Alarm
            alarm.setValue("test", forKey: "weekdays")
            alarm.setValue(String(alarmString), forKey: "time")
            fetchedCurrentMedicine.addAlarmObject(alarm)
        }
        do {
            try managedContext.save()
        } catch let error as NSError  {
            print("Could not save \(error), \(error.userInfo)")
        }

It keeps failing at 

fetchedCurrentMedicine.addAlarmObject(alarm)

and I get the error:

"'NSInvalidArgumentException', reason: 'NSManagedObjects of entity 'Medicine' do not support -mutableSetValueForKey: for the property 'alarms''"

Any idea where I may have messed up or gotten the schema of my data models wrong? Much appreciated.

Upvotes: 0

Views: 430

Answers (1)

evnaz
evnaz

Reputation: 190

On your data model screen alarms relation of Medicine model is to one. Perhaps medicines relation of Alarm model is to-many.
Anyway try to set to-many relation type for alarms in the data model inspector.

Upvotes: 2

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