https://habr.com/ru/company/badoo/blog/281162/

viper.swift

import UIKit

// MVC:

//struct Person { // Model
//    let firstName: String
//    let lastName: String
//}
//
//class GreetingViewController : UIViewController { // View + Controller
//    var person: Person!
//    let showGreetingButton = UIButton()
//    let greetingLabel = UILabel()
//
//    override func viewDidLoad() {
//        super.viewDidLoad()
//        self.showGreetingButton.addTarget(self, action: #selector(didTapButton(button:)), for: .touchUpInside)
//    }
//
//    @objc func didTapButton(button: UIButton) {
//        let greeting = "Hello" + " " + self.person.firstName + " " + self.person.lastName
//        self.greetingLabel.text = greeting
//
//    }
//    // layout code goes here
//}
//// Assembling of MVC
//let model = Person(firstName: "David", lastName: "Blaine")
//let view = GreetingViewController()
//view.person = model;


// MVP:

//struct Person { // Model
//    let firstName: String
//    let lastName: String
//}
//
//protocol GreetingView: class {
//    func setGreeting(greeting: String)
//}
//
//protocol GreetingViewPresenter {
//    init(view: GreetingView, person: Person)
//    func showGreeting()
//}
//
//class GreetingPresenter : GreetingViewPresenter {
//    unowned let view: GreetingView
//    let person: Person
//
//    required init(view: GreetingView, person: Person) {
//        self.view = view
//        self.person = person
//    }
//    func showGreeting() {
//        let greeting = "Hello" + " " + self.person.firstName + " " + self.person.lastName
//        self.view.setGreeting(greeting: greeting)
//    }
//}
//
//class GreetingViewController : UIViewController, GreetingView {
//    var presenter: GreetingViewPresenter!
//    let showGreetingButton = UIButton()
//    let greetingLabel = UILabel()
//
//    override func viewDidLoad() {
//        super.viewDidLoad()
//        self.showGreetingButton.addTarget(self, action: #selector(didTapButton(button:)), for: .touchUpInside)
//    }
//
//    @objc func didTapButton(button: UIButton) {
//        self.presenter.showGreeting()
//    }
//
//    func setGreeting(greeting: String) {
//        self.greetingLabel.text = greeting
//    }
//
//    // layout code goes here
//}
//// Assembling of MVP
//let model = Person(firstName: "David", lastName: "Blaine")
//let view = GreetingViewController()
//let presenter = GreetingPresenter(view: view, person: model)
//view.presenter = presenter


// MVVM:

//struct Person { // Model
//    let firstName: String
//    let lastName: String
//}
//
//protocol GreetingViewModelProtocol: class {
//    var greeting: String? { get }
//    var greetingDidChange: ((GreetingViewModelProtocol) -> ())? { get set } // function to call when greeting did change
//    init(person: Person)
//    func showGreeting()
//}
//
//class GreetingViewModel : GreetingViewModelProtocol {
//    let person: Person
//
//    var greeting: String? {
//        didSet {
//            self.greetingDidChange?(self)
//        }
//    }
//
//    var greetingDidChange: ((GreetingViewModelProtocol) -> ())?
//
//    required init(person: Person) {
//        self.person = person
//    }
//
//    func showGreeting() {
//        self.greeting = "Hello" + " " + self.person.firstName + " " + self.person.lastName
//    }
//}
//
//class GreetingViewController : UIViewController {
//    var viewModel: GreetingViewModelProtocol! {
//        didSet {
//            self.viewModel.greetingDidChange = { [unowned self] viewModel in
//                self.greetingLabel.text = viewModel.greeting
//            }
//        }
//    }
//    let showGreetingButton = UIButton()
//    let greetingLabel = UILabel()
//
//    override func viewDidLoad() {
//        super.viewDidLoad()
//        self.showGreetingButton.addTarget(self, action: #selector(didTapButton(button:)), for: .touchUpInside)
//    }
//
//    @objc func didTapButton(button: UIButton) {
//        self.viewModel.showGreeting()
//    }
//    // layout code goes here
//}
//// Assembling of MVVM
//let model = Person(firstName: "David", lastName: "Blaine")
//let viewModel = GreetingViewModel(person: model)
//let view = GreetingViewController()
//view.viewModel = viewModel


// VIPER:

struct Person { // Entity (usually more complex e.g. NSManagedObject)
    let firstName: String
    let lastName: String
}

struct GreetingData { // Transport data structure (not Entity)
    let greeting: String
    let subject: String
}

protocol GreetingProvider {
    func provideGreetingData()
}

protocol GreetingOutput: class {
    func receiveGreetingData(_ greetingData: GreetingData)
}

protocol GreetingViewEventHandler {
    func didTapShowGreetingButton()
}

protocol GreetingView: class {
    func setGreeting(_ greeting: String)
}

class GreetingInteractor : GreetingProvider {
    weak var output: GreetingOutput!
    
    func provideGreetingData() {
        let person = Person(firstName: "David", lastName: "Blaine") // usually comes from data access layer
        let subject = person.firstName + " " + person.lastName
        let greeting = GreetingData(greeting: "Hello", subject: subject)
        self.output.receiveGreetingData(greeting)
    }
}

class GreetingPresenter : GreetingOutput, GreetingViewEventHandler {
    weak var view: GreetingView!
    var greetingProvider: GreetingProvider!
    
    func didTapShowGreetingButton() {
        self.greetingProvider.provideGreetingData()
    }
    
    func receiveGreetingData(_ greetingData: GreetingData) {
        let greeting = greetingData.greeting + " " + greetingData.subject
        self.view.setGreeting(greeting)
    }
}

class GreetingViewController : UIViewController, GreetingView {
    var eventHandler: GreetingViewEventHandler!
    let showGreetingButton = UIButton()
    let greetingLabel = UILabel()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.showGreetingButton.addTarget(self, action: #selector(didTapButton(button:)), for: .touchUpInside)
    }
    
    @objc func didTapButton(button: UIButton) {
        self.eventHandler.didTapShowGreetingButton()
    }
    
    func setGreeting(_ greeting: String) {
        self.greetingLabel.text = greeting
    }
    
    // layout code goes here
}
// Assembling of VIPER module, without Router
let view = GreetingViewController()
let presenter = GreetingPresenter()
let interactor = GreetingInteractor()
view.eventHandler = presenter
presenter.view = view
presenter.greetingProvider = interactor
interactor.output = presenter