AppDelegate.swift

// ...
import CoreData
// ...

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
  // ...
  
  // MARK: - Core Data stack
  lazy var persistentContainer: NSPersistentContainer = {
    let container = NSPersistentContainer(name: "AudioCache")
    container.loadPersistentStores { description, error in
      if let error = error {
        fatalError("Unable to load persistent stores: \(error)")
      }
    }
    return container
  }()
  
  // MARK: - Core Data Saving support
  func saveContext() {
    let context = persistentContainer.viewContext
    if context.hasChanges {
      do {
        try context.save()
      } catch let error as NSError {
        print("Error: \(error), \(error.userInfo)")
      }
    }
  }
  
  // ...
}