UIStoryboard+Extensions.swift

import Foundation
import UIKit

extension UIStoryboard {

    enum Storyboard {
        case main
        case order
        
        var name: String {
            switch self {
            case .main:
                return "Main"
            case .order:
                return "Order"
            }
        }
    }

    convenience init(storyboard: Storyboard, bundle: Bundle? = nil) {
        self.init(name: storyboard.rawValue, bundle: bundle)
    }

}

protocol StoryboardIdentifiable {
    static var storyboardIdentifier: String { get }
}

extension StoryboardIdentifiable where Self: UIViewController {
    static var storyboardIdentifier: String {
        return String(describing: self)
    }
}

extension UIViewController: StoryboardIdentifiable { }

extension UIStoryboard {

    func instantiateViewController<T: UIViewController>() -> T {

        let optionalViewController = self.instantiateViewController(withIdentifier: T.storyboardIdentifier)

        guard let viewController = optionalViewController as? T else {
            fatalError("Couldn't instantiate view controller with identifier \(T.storyboardIdentifier)")
        }

        return viewController
    }

    func instantiateViewController<T: UIViewController>(_: T.Type) -> T {

        let optionalViewController = self.instantiateViewController(withIdentifier: T.storyboardIdentifier)

        guard let viewController = optionalViewController as? T else {
            fatalError("Couldn't instantiate view controller with identifier \(T.storyboardIdentifier)")
        }

        return viewController
    }
}