Swift - how to pass managed object context to different view controllers - swift

Question

I put the core data stack in its own file as shown below. I read that using dependency injection is the best way to pass the managed object context. So in each of a handful of VCs, I declare the following property:
var managedObjectContext: NSManagedObjectContext?
Now, the tricky part is getting the moc from my stack to the different VCs. Which seems like a great place for a singleton, but assuming that's a bad idea, I guess I would use the code below in CoreDataStack:
let controller = self.window!.rootViewController as! ViewController
let context = self.persistentContainer.viewContext
controller.managedObjectContext = context
But that leaves me with a few questions:
1) Where in CoreDataStack should I include the code above? In the App Delegate it would go in didFinishLaunchingWithOptions, but that's not really an option now.
2) Writing the above code for every single vc that needs a context seems bad. I guess I could loop through all the VCs. I've seen the moc passed using didSet too, but that doesn't seem quite right either.
CoreData Stack
class CoreDataStack {
lazy var persistentContainer: NSPersistentContainer = {
let container = NSPersistentContainer(name: "Model")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
return container
}()
func saveContext () {
let context = persistentContainer.viewContext
if context.hasChanges {
do {
try context.save()
} catch {
let nserror = error as NSError
fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
}
}
}