NSManagedObject collection properties become nil after a while - swift

Question

I'm working in a subclass of NSViewController where in viewDidLoad I fetch my entities from CoreData as below:
let delegate = AppDelegate.init()
let context = delegate.persistentContainer.viewContext
let fetch = PicPathEntity.entityFetchRequest()
var tempEntities: [PicPathEntity] = []
context.performAndWait {
tempEntities = try! fetch.execute()
}
entities = tempEntities
Then during the itemForRepresentedObjectAt function, it appears that the count of entities is the same, but the property values have become nil/empty.
I did some searching and found similar problems with no clear answers (at least not for Swift)
I can't seem to find information on how to properly fetch and retain the data in my entities variable.

Answer 1

I figured out how to solve this after reading the how the relationship between objects and context work.
Turns out all I needed to make this work, was make the context into a property of the ViewController instead of a local variable of viewDidLoad.
var entities: [PicPathEntity] = []
var context: NSManagedObjectContext!
override func viewDidLoad() {
super.viewDidLoad()
let delegate = AppDelegate.init()
context = delegate.persistentContainer.viewContext
let fetch = PicPathEntity.entityFetchRequest()
context.performAndWait {
entities = try! fetch.execute()
}
}
Due to helpful comments to this answer, I have now updated the code to:
var entities: [PicPathEntity] = []
var context: NSManagedObjectContext!
override func viewDidLoad() {
super.viewDidLoad()
let delegate = NSApplication.shared.delegate as! AppDelegate
context = delegate.persistentContainer.viewContext
let fetch = PicPathEntity.entityFetchRequest()
context.perform {
self.entities = try! fetch.execute()
self.picFinderEntityCollectionView.reloadData()
}
configureCollectionView()
}