Author: Sean Allen Video URL: Intro to Programatic UI. No Storyboard – Swift – Xcode 10 Introduction: In this video we build the basic structure of an app without using storyboards. We take a programatic approach to showing the initial screen, creating a UINavigationController, adding a UIButton to the screen, and transitioning to a new screen. This is just the beginning o your programatic UI journey!

Could not find a storyboard named ‘Main’ in bundle NSBundle

Add initial view controller

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

        let vc = ViewController()
        
        window = UIWindow(frame: UIScreen.main.bounds)
        window?.rootViewController = vc
        window?.makeKeyAndVisible()
        
        return true
    }

Set Constraints by codes

    func setNextButtonConstraints() {
        nextButton.translatesAutoresizingMaskIntoConstraints = false
        nextButton.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20).isActive = true
        nextButton.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20).isActive = true
        nextButton.heightAnchor.constraint(equalToConstant: 50).isActive = true
        nextButton.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
    }

Add target for the button

/* This will add the specific target of "nextButtonTapped" to nextButton. */
nextButton.addTarget(self, action: #selector(nextButtonTapped), for: .touchUpInside)

/* The target function looks like as follows. */
@objc func nextButtonTapped() {
    /* TODO */
}