CODEWITHSUNDEEP
swiftcore-data
da1lbi3
da1lbi3

Reputation: 4519

CoreData: error: Failed to call designated initializer on NSManagedObject custom class

When I call the function CacheStation I get the error: CoreData: error: Failed to call designated initializer on NSManagedObject class SaveModel. Nothing more nothing less. How can I resolve this issue?

SaveModel.swift: 

import Foundation
    import CoreData
    import UIKit

class SaveModel: NSManagedObject {

    func CacheStations(){
        // create an instance of our managedObjectContext
        let moc = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext

        // we set up our entity by selecting the entity and context that we're targeting
        let entity = NSEntityDescription.insertNewObjectForEntityForName("CachedStations", inManagedObjectContext: moc) as! SaveModel

        //add the data
        entity.land = "nl";

        // we save our entity
        do {
            try moc.save()
        } catch {
            fatalError("Failure to save context: \(error)")
        }
}

SaveModel+CoreDataProperties.swift:

import Foundation
import CoreData

extension SaveModel {
    @NSManaged var land: String?
}

Where I call CacheStations:

import UIKit

class ViewController: UIViewController {

    @IBAction func saveShizzle(sender: AnyObject) {
        let sm = SaveModel();
        sm.CacheStations();
    }
}

Upvotes: 2

Views: 1193

Answers (2)

pbasdf
pbasdf

Reputation: 21536

This line:

let sm = SaveModel();

uses the standard init() method to create an instance of SaveModel, but NSManagedObjects must be initialised using the designated initialiser:

init(entity entity: NSEntityDescription, insertIntoManagedObjectContext context: NSManagedObjectContext?)

(or, as in your CacheStations method, using NSEntityDescription.insertNewObjectForEntityForName(_, inManagedObjectContext: moc) which calls the designated initialiser).

Since it seems sm is created only to have an instance on which to call CacheStations, I would change that method to a class method:

class func CacheStations(){

and change your saveShizzle method to use the class method:

@IBAction func saveShizzle(sender: AnyObject) {
    SaveModel.CacheStations();
}

Upvotes: 2

Tom Harrington
Tom Harrington

Reputation: 70936

Here's what happens:

  1. When you call let sm = SaveModel(); you are creating a new instance of SaveModel.
  2. SaveModel is a subclass of NSManagedObject
  3. NSManagedObject has a designated initializer called init(_: insertIntoManagedObjectContext:)
  4. Your subclass does not add any initializers of any kind, which means that you must call the superclass designated initializer.
  5. You don't do this, so you get an error message which describes the exact problem.

You need to either call the NSManagedObject designated initializer or create your own designated initializer that calls the superclass designated initializer.

Upvotes: 0

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