Guideline to choose best iOS Architecture Patterns
Introduction#
Demystifying MVC, MVP, MVVM and VIPER or any other design patterns to choose the best approach to building an app
MVC pattern
import UIKit
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: "didTapButton:", forControlEvents: .TouchUpInside)
}
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 Patterns
import UIKit
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)
}
}
class GreetingViewController : UIViewController, GreetingView {
var presenter: GreetingViewPresenter!
let showGreetingButton = UIButton()
let greetingLabel = UILabel()
override func viewDidLoad() {
super.viewDidLoad()
self.showGreetingButton.addTarget(self, action: "didTapButton:", forControlEvents: .TouchUpInside)
}
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 Pattern
import UIKit
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.viewModel, action: "showGreeting", forControlEvents: .TouchUpInside)
}
// 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 Pattern
import UIKit
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)
}
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)
}
}
protocol GreetingViewEventHandler {
func didTapShowGreetingButton()
}
protocol GreetingView: class {
func setGreeting(greeting: String)
}
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: "didTapButton:", forControlEvents: .TouchUpInside)
}
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