Swift 3 Core Data - ios

Question

I am getting the following error while trying to do NSFetchRequest in Swift 3
Generic parameter 'ResultType' could not be inferred
i checked lots of links and i have not been able to figure how to solve it.
this is what am doing
ViewController.swift
func loadData(){
let request = NSFetchRequest(entityName: "Grocery") //Error occurs here(Generic parameter 'ResultType' could not be inferred)
do{
let results = try manageObjectContext.execute(request)
groceries = results as! [NSManagedObject]
tableView.reloadData()
}catch{
fatalError("Error is retriving Gorcery items")
}
}

Answer 1

Try this:
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Grocery")
It should work :)
Therefore your code should Look like:
func loadData(){
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Grocery")
do{
let results = try manageObjectContext.execute(request)
groceries = results as! [NSManagedObject]
tableView.reloadData()
}catch{
fatalError("Error is retriving Gorcery items")
}
}

Answer 2

Credits: Nitesh Patil https://medium.com/#imnitpa/swift-3-core-data-7b00b50f5782
import UIKit
import CoreData
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .white
let appDelegate = UIApplication.shared.delegate as!AppDelegate
let context = appDelegate.persistentContainer.viewContext
//adding new user and saving in database...
let newUser = NSEntityDescription.insertNewObject(forEntityName: "Users", into: context)
newUser.setValue("Batman", forKey: "username")
newUser.setValue("Robin", forKey: "password")
do {
try context.save()
print("saved")
} catch {
print("Error occured...")
}
// restoring data back from database
let request = NSFetchRequest < NSFetchRequestResult > (entityName: "Users")
request.returnsObjectsAsFaults = false
do {
let results =
try context.fetch(request)
if results.count > 0 {
for result in results as![NSManagedObject] {
if let username = result.value(forKey: "username") as ? String {
print(username)
}
}
}
else {
print("No results")
}
} catch {
print("Couldn't fetch results")
}
}
}

Answer 3

you can use this too:
let request : NSFetchRequest<Grocery> = Grocery.fetchRequest()
and you get results of the type [Grocery] when you execute the request:
let results : [Grocery] = try manageObjectContext.execute(request)
or
let results = try manageObjectContext.execute(request)