CoreInnerLayer.swift

// Abstract
protocol NavigationController {
  func push(_ view: View)
}
protocol View {}
protocol Service {
  func fetchUser() -> User
  func write(user: User)
}

// Concrete
struct User {
  let name: String
}

class Router {
  let navigationController: NavigationController // abstract
  @Dependency(\.userViewFactory) var userViewFactory // abstract
  func show(user: User) {
    let view = userViewFactory.make(user)
    let presenter = PresenterB(interactor: InteractorB(), router: RouterB())
    presenter.delegate = view
    view.presenter = presenter
    navigationController.push(view)
  }
}

class Presenter {
  weak var delegate: View? // abstract
  let interactor: Interactor // concrete
  let router: Router // concrete
  func prepare() {
    interactor.fetchUser()
  }
  func store(user: User) {
    interactor.store(user)
  }
  func show(user: User) {
    router.show(user)
  }
}

class Interactor {
  weak var delegate: Presenter?
  @Dependency(\.service) var service // abstract
  func fetchUser() {
    delegate?.show(user: service.fetchUser())
  }
  func store(user: User) {
    service.write(user)
  }
}