How do I create a new Swift project without using Storyboards?

If you want to Initialize your viewController with xib and and need to use navigation controller. Here is a piece of code.

var window: UIWindow?
var navController:UINavigationController?
var viewController:ViewController?

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    window = UIWindow(frame: UIScreen.mainScreen().bounds)

    viewController = ViewController(nibName: "ViewController", bundle: nil);
    navController = UINavigationController(rootViewController: viewController!);

    window?.rootViewController = navController;
    window?.makeKeyAndVisible()

    return true
}

All it takes for not using Storyboards for the rootViewController:

1· Change AppDelegate.swift to:

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey : Any]? = nil) -> Bool {
        window = UIWindow(frame: UIScreen.main.bounds)
        if let window = window {
            window.backgroundColor = UIColor.white
            window.rootViewController = ViewController()
            window.makeKeyAndVisible()
        }
        return true
    }
}

2· Create a ViewController subclass of UIViewController:

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = UIColor.blue
    }
}

3· If you created the project from an Xcode template:

1. Remove the key-value pair for key "Main storyboard file base name" from Info.plist.
2. Delete the storyboard file Main.storyboard.

As you can see in the first code snippet, instead of implicitly unwrapping an optional, I rather like the if let syntax for unwrapping the optional window property. Here I'm using it like if let a = a { } so that the optional a becomes a non-optional reference inside the if-statement with the same name – a.

Finally self. is not necessary when referencing the window property inside it own class.

You must mark the window and testNavigationController variables as optional:

var window : UIWindow?
var testNavigationController : UINavigationController?

Swift classes require non-optional properties to be initialized during the instantiation:

Classes and structures must set all of their stored properties to an appropriate initial value by the time an instance of that class or structure is created. Stored properties cannot be left in an indeterminate state.

Properties of optional type are automatically initialized with a value of nil, indicating that the property is deliberately intended to have “no value yet” during initialization.

When using optional variables, remember to unwrap them with !, such as:

self.window!.backgroundColor = UIColor.whiteColor();