ios - Swift CoreData: error: Failed to call designated initializer on NSManagedObject class 'NSManagedObject'

Question

I'm using core data to save a category in vc1 and want to add list properties to a list in vc2. My data model is one category to many list properties.

I'm adding the category like this in vc1:

func createNewCategory() {
    var category: NSManagedObject! = NSEntityDescription.insertNewObjectForEntityForName("Category", inManagedObjectContext: self.context) as NSManagedObject
    category.setValue(self.categoryTextField.text, forKey: "name")

    var error: NSError? = nil
    self.context.save(&error)
}

Setting up the data in vc2:

func setupCoreData() {
    var appDelegate: AppDelegate = (UIApplication.sharedApplication()).delegate as AppDelegate
    self.context = appDelegate.managedObjectContext!

    var request: NSFetchRequest = NSFetchRequest(entityName: "Category")
    if (self.context.executeFetchRequest(request, error: nil)) {
        var error: NSError? = nil
        self.listData = self.context.executeFetchRequest(request, error: &error)
        self.managedObject = self.listData.objectAtIndex(0) as NSManagedObject
    }
}

It crashes on the last row: self.managedObject = ... saying:

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

The managed object is in the array if I put a break point and print the array. What's wrong?

Answer 1

The dedicated initializer is

class func insertNewObjectForEntityForName(_ entityName: String!,
   inManagedObjectContext context: NSManagedObjectContext!) -> AnyObject!

Clearly, you are not inserting a new object, so you really want an optional value. Maybe you declared your class variable managedObject as NSManagedObject!? Try setting it to NSManagedObject? and also change the operator to as?.