Simple extension to observe CoreData NSManagedObjects, behaves like the observe function in Realm.

NSManagedObjectExtension.swift

//
//  NSManagedObjectExtension.swift
//
//  Created by Karim Abou Zeid on 10.06.18.
//  Copyright © 2018 Karim Abou Zeid Software. All rights reserved.
//

import CoreData

extension NSManagedObject {
    typealias OnChange = (ChangeType) -> ()

    func observe(_ onChange: @escaping OnChange) -> NotificationToken {
        return NotificationToken(object: self, onChange: onChange)
    }

    public enum ChangeType {
        case change([String : Any])
        case deleted
    }

    public class NotificationToken {
        let onChange: OnChange
        let object: NSManagedObject

        init(object: NSManagedObject, onChange: @escaping OnChange) {
            self.object = object
            self.onChange = onChange
            NotificationCenter.default.addObserver(self,
                                                   selector: #selector(contextObjectsDidChange(_:)),
                                                   name: Notification.Name.NSManagedObjectContextObjectsDidChange,
                                                   object: object.managedObjectContext)
        }

        deinit {
            NotificationCenter.default.removeObserver(self)
        }

        @objc
        func contextObjectsDidChange(_ notification: Notification) {
            if let objects = notification.userInfo?[NSInsertedObjectsKey] as? Set<NSManagedObject> {
                if objects.contains(object) {
                    onChange(.change(object.changedValuesForCurrentEvent()))
                }
            }
            if let objects = notification.userInfo?[NSUpdatedObjectsKey] as? Set<NSManagedObject> {
                if objects.contains(object) {
                    onChange(.change(object.changedValuesForCurrentEvent()))
                }
            }
            if let objects = notification.userInfo?[NSDeletedObjectsKey] as? Set<NSManagedObject> {
                if objects.contains(object) {
                    onChange(.deleted)
                }
            }
            if let objects = notification.userInfo?[NSRefreshedObjectsKey] as? Set<NSManagedObject> {
                if objects.contains(object) {
                    onChange(.change(object.changedValuesForCurrentEvent()))
                }
            }
            if let objects = notification.userInfo?[NSInvalidatedObjectsKey] as? Set<NSManagedObject> {
                if objects.contains(object) {
                    onChange(.deleted)
                }
            }
            if notification.userInfo?[NSInvalidatedAllObjectsKey] != nil {
                onChange(.deleted)
            }
        }
    }
}

I try this code does work for me 👍