使用 MVVM 架构时页面跳转逻辑写在哪儿？

typealias Completion = () -> Void

enum PageMap {
    case DemoPage1
    case DemoPage2(String)

    var vc: UIViewController {
        switch self {
        case .DemoPage:
            return DemoController1()
        case .DemoPage2(let title):
            return DemoController2(title: title)
        }
    }
}

enum Router {
    case Push(PageMap)
    case Present(PageMap)

    func go(form vc: UIViewController,
                 animated: Bool = true,
                 completion: Completion? = nil) {

        switch self {
        case .Push(let map):
            vc.navigationController?.pushViewController(map.vc, animated: animated)
        case .Present(let map):
            vc.presentViewController(map.vc, animated: animated, completion: completion)
        }
    }
}