Ggtcf

If I have an Xcode project that already uses a Storyboard, and now I want to switch to loading the view controller programmatically, how do I do that?

Here is an in-depth article about doing this. The TLDR is:

1. In the project settings, clear the Main Interface:

2. 
   

   In your didFinishLaunching use code such as the following:

   
   
   

   func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool 
    window = UIWindow(frame: UIScreen.main.bounds)
    let homeViewController = UIViewController()
    homeViewController.view.backgroundColor = UIColor.red
    window!.rootViewController = homeViewController
    window!.makeKeyAndVisible()
    return true
   
   

   
   

Slowly. One step at a time.

Storyboards are not all-or-nothing. You can continue to use a Storyboard for places where it is helpful, and you can use programmatic loading for places where it isn't, and you can transition between them one step at a time.

A first step if you wanted to unwind a piece from the Storyboard is to remove the segues leading in and out of it, and then programmatically load that view controller from the Storyboard with instantiateViewController(withIdentifier:).

You could then pull a given scene into its own separate Storyboard (select the scene, Editor, Refactor to Storyboard...) so that it's completely independent of all the other scenes. Then you can rework that one view controller as programmatic code without interrupting anything else in the project. You can also mix-and-match here; loading the view controller from the Storyboard, but handling initialization by hand in init(nibName:bundle:).

You can also cut and paste a storyboard view into its own XIB file, which sometimes is easier to work with, without giving up the GUI layout system. Select the view, copy, create a new XIB file (it's called "View" in the templates), and paste it. This is a bit easier to use with init(nibName:bundle:).

But the key point is to not try to rework your entire project all at once. If there's some portion where Storyboards are causing trouble, refactor them out. If you just like programmatic code better, then keep refactoring one step at a time until you're done or until you've done enough to be happy.

As Senseful's answer notes, the top-level scene is slightly special. You can change it with or without changing the other scenes.