Each standard view controller has a corresponding superclass (listed in the Scenes and view controllers section previously in this chapter). This can be replaced with a custom subclass, which then has the ability to influence and change what happens in the user interface. To replace the message in the Message Scene, create a new file named MessageViewCotroller.swift with the following content:

import UIKit
class MessageViewController: UIViewController {
}

Having created the class, it can be associated with the view controller by selecting it in the storyboard and then switching to the identity inspector by navigating to View | Utilities | Show Identity Inspector or pressing Command + Option...