Concept

VIPERConcept.swift

class Presenter<T> {
    private var view: T?
    func attachView(_ view: T) {
        self.view = view
    }
    
    func detachView() {
        self.view = nil
    }
}

struct UserDTO {
    let firstName: String
    let lastName: String
}

protocol DataStore {
    func getUser() -> UserDTO
}

class UserDataStore: DataStore {
    func getUser() -> UserDTO {
        return UserDTO(firstName: "Mary", lastName: "Jane")
    }
}

class UserInteractor<T: DataStore> {
    struct User {
        let firstName: String
        let lastName: String
    }
    
    private let dataStore: T
    
    init(dataStore: T) {
        self.dataStore = dataStore
    }
    
    func getUser() -> User {
        let dtoUser = dataStore.getUser()
        return User(firstName: dtoUser.firstName, lastName: dtoUser.lastName)
    }
}

protocol UserView {
    func setFirstName(_ firstName: String)
    func setLastName(_ lastName: String)
}

class UserPresenter<T: UserView, U: UserDataStore>: Presenter<T> {
    private let interactor: UserInteractor<U>
    
    init(interactor: UserInteractor<U>) {
        self.interactor = interactor
    }
    
    override func attachView(_ view: T) {
        super.attachView(view)
        
        let user = interactor.getUser()
        view.setFirstName(user.firstName)
        view.setLastName(user.lastName)
    }
}

class UserViewController: UIViewController, UserView {
    func setFirstName(_ firstName: String) {
        debugPrint("First name = \(firstName)")
    }
    
    func setLastName(_ lastName: String) {
        debugPrint("Last name = \(lastName)")
    }
}

let myInteractor = UserInteractor<UserDataStore>(dataStore: UserDataStore())
let myPresenter = UserPresenter<UserViewController, UserDataStore>(interactor: myInteractor)
myPresenter.attachView(UserViewController(nibName: nil, bundle: nil))