Getting nil after delete an object in Coredata Swift - ios

Question

I tried to store some data using CoreData.
I created Entity Name Users and some attributes namely age, username, password.
Successfully loading, retrieving.
When I delete some object in that entity using context.delete(user), It will be deleted but show nil after I retrieving again.
Showing nil for deleted object
Note: I write the code for predicate which format is "Username!=nil".
Is this the right way? or how to overcome without nil in core data?
import UIKit
import CoreData
class CoreDataVC: UIViewController {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
var context:NSManagedObjectContext!
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func addAction(_ sender: Any){
if let newUser = openDatabse(){
saveData(UserDBObj:newUser)
}
_ = fetchData()
}
#IBAction func deleteAction(_ sender: Any){
if let newUser = openDatabse(){
deleteData(UserObj: newUser)
}
_ = fetchData()
}
// MARK: Methods to Open, Store and Fetch data
func openDatabse() -> NSManagedObject?{
context = appDelegate.persistentContainer.viewContext
guard let entity = NSEntityDescription.entity(forEntityName: "Users", in: context) else {
print("Invalid Entity")
return nil
}
let newUser = NSManagedObject(entity: entity, insertInto: context)
return newUser
}
func deleteData(UserObj: NSManagedObject){
let result = self.fetchData()
if let data = result.last{
context.delete(data)
}
do {
try context.save()
}
catch{
print("Error on saving context")
}
_ = fetchData()
}
func saveData(UserDBObj:NSManagedObject)
{
UserDBObj.setValue("RDC1", forKey: "username")
UserDBObj.setValue("12341", forKey: "password")
UserDBObj.setValue("22", forKey: "age")
print("Storing Data..")
do {
try context.save()
} catch {
print("Storing data Failed")
}
_ = fetchData()
}
func fetchData() -> [Users]
{
var users : [Users] = []
print("Fetching Data..")
let request = Users.fetchRequest()
request.returnsObjectsAsFaults = false
do {
let result = try context.fetch(request)
users = result
for data in result {//as! [NSManagedObject] {
print("Username: ",data.username ?? "nil",", Age : ",data.age ?? "nil")
}
} catch {
print("Fetching data Failed")
}
return users
}
}
Thanks in Advance.