Navigator

Navigator.swift

struct Navigator {
    static func toMainViewController(from parent: UIViewController) {
        self.present(from: parent, to: StoryboardBuilder.mainViewController)
    }

    // 遷移先のViewControllerに値を渡す場合 
    static func toDetailViewController(from parent: UIViewController, id: String) {
        let detail = StoryboardBuilder.detailViewController
        detail.id = id
        self.present(from: parent, to: detail)
    }

    private static func present(from parent: UIViewController, to content: UIViewController) {
        parent.present(content, animated: true, completion: nil)
    }
}

StoryboardBuilder.swift

struct StoryboardBuilder {
    private static func storyboard(name: StoryboardName) -> UIStoryboard {
        return UIStoryboard(name: name.rawValue, bundle: Bundle.main)
    }

    private static func viewController<T: UIViewController>(name: StoryboardName, id: StoryboardID) -> T {
        guard let vc = storyboard(name: name).instantiateViewController(withIdentifier: id.rawValue) as? T else {
            fatalError("Error: StoryboardBuilder: No cast ViewControllerType from storyboard to ReturnValueType")
        }
        return vc
    }

    static var mainViewController: MainViewController {
        return viewController(name: .Main, id: .MainViewController)
    }

  static var detailViewController: DetailViewController {
        return viewController(name: .Detail, id: .DetailViewController)
    }
}

StoryboardID.swift

enum StoryboardID: String {
    case MainViewController
    case DetailViewController
}

StoryboardName.swift

// XXX.storyboardのXXXの部分
enum StoryboardName: String {
    case Main
    case Detail
}

Usage.swift

func onClickButtonToMain() {
    Navigator.toMainViewController(from: self)
}

func onClickButtonToDetail() {
    Navigator.toDetailViewController(from: self)
}