An instance of NSFetchedResultsController requires a non-nil fetchRequest and managedObjectContext'

Question

Other people have asked a similar question, but the answers given did not help me. I am trying to create a table view with core data and I keep getting an error message that my fetchRequest and/or managedObjectContext are nil

class CustomTableViewController: UITableViewController, 
NSFetchedResultsControllerDelegate {

var coreDataContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext


@available(iOS 10.0, *)
fileprivate lazy var fetchedResultsController: NSFetchedResultsController<Movie> = {
    // Initiate the query
    let fetchRequest: NSFetchRequest<Movie> = Movie.fetchRequest() as! NSFetchRequest<Movie>

    // Sort the data
    fetchRequest.sortDescriptors = [NSSortDescriptor(key:"title", ascending: true)]

  NSLog("Request: %@, Context: %@", fetchRequest, self.coreDataContext);        
  let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: self.coreDataContext, sectionNameKeyPath: nil, cacheName: nil)

    fetchedResultsController.delegate = self
    return fetchedResultsController
}()


override func viewDidLoad() {
    super.viewDidLoad()

    navigationController?.setToolbarHidden(false, animated: false)

    do {
        // when view loads, run the fetch (query)
        if #available(iOS 10.0, *) {
            try self.fetchedResultsController.performFetch()
        } else {
            // Fallback on earlier versions
        }
    } catch {
        let fetchError = error as NSError
        print("Unable to Perform Fetch Request")
        print("\(fetchError)")
    }
    }

Does anyone have any ideas what's wrong? Also, not sure if it matters, but my project is a mix of both Objective-C and Swift

Also, the NSLog("Request: %@, Context: %@", fetchRequest, self.coreDataContext) from my above code prints out:

Request: (null), Context: <NSManagedObjectContext: 0x1701db4e0>

I have an entity called Movie in my xcdatamodeld with three String attributes. I also created a class for Movie like this in its own Movie.swift file:

import UIKit
import CoreData

class Movie: NSManagedObject {

}

Answer 1

The problem is that your Movie class has no code for generating a fetch request.

@nonobjc public class func fetchRequest() -> NSFetchRequest<Movie> {
    return NSFetchRequest<Movie>(entityName: "Movie");
}

The solution: Delete your Movie class file entirely.

In the data model, configure your Movie entity to do automatic code generation:

That will solve the problem. Xcode knows how to make the class files for an entity. So just permit it to do so, and all will be well.