A MVP demo

mvp.playground.swift

//: A UIKit based Playground for presenting user interface

import UIKit
import PlaygroundSupport

struct User {
  let firstName: String
  let lastName: String
  let email: String
  let age: Int
}

class UserService {
  
  //the service delivers mocked data with a delay
  func getUsers(callBack:@escaping ([User]) -> Void) {
    let users = [User(firstName: "Iyad", lastName: "Agha", email: "[email protected]", age: 36),
                 User(firstName: "Mila", lastName: "Haward", email: "[email protected]", age: 24),
                 User(firstName: "Mark", lastName: "Astun", email: "[email protected]", age: 39)
    ]
    
    DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 2) {
      callBack(users)
    }
  }
}

// data passed to view because view doesn't need to know the model itself
struct UserViewData {
  let name: String
  let age: String
}

protocol UserView: class {
  func startLoading()
  func finishLoading()
  func setUsers(users: [UserViewData])
}

class UserPresenter {
  private let userService:UserService
  weak private var userView : UserView?
  
  init(userService:UserService){
    self.userService = userService
  }
  
  func attachView(view:UserView){
    userView = view
  }
  
  func detachView() {
    userView = nil
  }
  
  func getUsers(){
    print("getUsers")
    self.userView?.startLoading()
    userService.getUsers{ [weak self] users in
      self?.userView?.finishLoading()
      if(users.count == 0){
        self?.userView?.setUsers(users:[])
      }else{
        let mappedUsers = users.map {
          return UserViewData(name: "\($0.firstName) \($0.lastName)", age: "\($0.age) years")
        }
        self?.userView?.setUsers(users: mappedUsers)
      }
      
    }
  }
}

class MyViewController : UIViewController {
  var emptyView: UIView?
  var tableView: UITableView?
  var activityIndicator: UIActivityIndicatorView? // TODO: To be implemented
  
  private weak var userPresenter: UserPresenter!
  private var usersToDisplay = [UserViewData]() // covert from model to ViewModel
  
  init(presenter: UserPresenter) {
    super.init(nibName: nil, bundle: nil)
    
    self.userPresenter = presenter
    self.userPresenter.attachView(view: self)
  }
  
  required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }
  
  override func loadView() {
    print("loadView")
    view = UIView()
    view.backgroundColor = UIColor.white
    
    setupEmptyView()
    setupTableView()
  }
  
  override func viewDidLoad() {
    super.viewDidLoad()
    
    print("viewDidLoad")
    
    setupIndicator()
    self.userPresenter.getUsers()
  }
  
  private func setupEmptyView() {
    emptyView = UIView()
    emptyView!.backgroundColor = .yellow
    view.addSubview(emptyView!)
    
    setupConstraints(for: emptyView!)
  }
  
  private func setupTableView() {
    tableView = UITableView()
    view.addSubview(tableView!)
    
    setupConstraints(for: tableView!)
    
    tableView?.delegate = self
    tableView?.dataSource = self
    
    tableView?.register(UITableViewCell.self, forCellReuseIdentifier: "UserCell")
  }
  
  private func setupIndicator() {
    activityIndicator = UIActivityIndicatorView(style: UIActivityIndicatorView.Style.gray)
    
    activityIndicator!.hidesWhenStopped = true
    view.addSubview(activityIndicator!)
    
    activityIndicator!.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
      activityIndicator!.centerXAnchor.constraint(equalTo: self.view.centerXAnchor),
      activityIndicator!.centerYAnchor.constraint(equalTo: self.view.centerYAnchor)
    ])
  }
  
  private func setupConstraints(for view: UIView) {
    view.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
      view.topAnchor.constraint(equalTo: self.view.topAnchor, constant: 0),
      view.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 0),
      view.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: 0),
      view.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: 0),
      ])
  }
}

extension MyViewController: UserView {
  func startLoading() {
    activityIndicator?.startAnimating()
  }
  
  func finishLoading() {
    activityIndicator?.stopAnimating()
  }
  
  func setUsers(users: [UserViewData]) {
    if users.isEmpty {
      self.emptyView?.isHidden = false
      self.tableView?.isHidden = true
    } else {
      self.emptyView?.isHidden = true
      self.tableView?.isHidden = false
      usersToDisplay = users
      tableView?.reloadData()
    }
  }
}

extension MyViewController: UITableViewDataSource, UITableViewDelegate {
  func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return usersToDisplay.count
  }
  
  func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = UITableViewCell(style: UITableViewCell.CellStyle.subtitle, reuseIdentifier: "UserCell")
    let userViewData = usersToDisplay[indexPath.row]
    cell.textLabel?.text = userViewData.name
    cell.detailTextLabel?.text = userViewData.age
    cell.textLabel
    return cell
  }
  
  
}

// Present the view controller in the Live View window
let presenter = UserPresenter(userService: UserService())
let vc = MyViewController(presenter: presenter)

PlaygroundPage.current.liveView = vc
//PlaygroundPage.current.needsIndefiniteExecution = true