UIViewController+StoryboardInit.swift

import UIKit

extension UIViewController {
    /// Creates an instance of `ViewControllerType` defined in a storyboard.
    ///
    /// The setup for this method to work is the following:
    /// 1. The storyboard needs to have a single view controller of the type `ViewControllerType`
    /// 2. This view controller needs to be set as the initial view controller
    /// 3. The name of the view controller needs to match the name of the storyboard and end with "ViewController".
    ///   e.g. Some.storyboard and SomeViewController
    static func initFromStoryboard<ViewControllerType: UIViewController>() -> ViewControllerType {
        let bundle = Bundle(for: self)
        let name = String(describing: self).replacingOccurrences(of: "ViewController", with: "")
        let storyboard = UIStoryboard(name: name, bundle: bundle)

        guard let viewController = storyboard.instantiateInitialViewController() as? ViewControllerType else {
            let error = """
            ViewController of type \(self) failed to instantiate.
            Check if the ViewController is set as initial in the Storyboard
            and that it's set to a correct custom class.
            """
            fatalError(error)
        }
        return viewController
    }
}