如何在Xcode8中使用Swift 3创建managedObjectContext？

import CoreData

var persistentContainer: NSPersistentContainer!
var managedObjectContext: NSManagedObjectContext {
    return persistentContainer.viewContext
}

func saveContext() {
    if managedObjectContext.hasChanges {
        do {
            try managedObjectContext.save()
        } catch {
            let nserror = error as NSError
            fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
        }
    }
}

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    persistentContainer = NSPersistentContainer(name: "YourDataModelFileName")
    persistentContainer.loadPersistentStores { (storeDescription, error) in
        if let error = error as NSError? {
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    }
    return true
}

let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managedObjectContext = appDelegate.managedObjectContext