onmyway133

class ViewModel {
  class Input {
    let fetch = PublishSubject<()>()
  }
  class Output {
    let friends: Driver<[User]>
  }
  let apiClient: APIClient
  let input: Input
  let output: Output

onmyway133

let facebookFriends: Observable<[User]> // network request
let twitterFriends: Observable<[User]> // network request
let totalFriends: Observable<[User]> = Observable.combineLatest([facebookFriends, twitterFriends]) { friends in
  return Array(friends.joined())
}

onmyway133

override func viewDidLoad() {
  super.viewDidLoad()
  viewModel.friends.subscribe(onNext: { friends in
    self.friendsCountLabel.text = "\(friends.count)"
  })
}

onmyway133

class ViewModel {
  let friends: Observable<[User]>
  init() {
    let client = APIClient()
    friends = Observable<[User]>.create({ subscriber in
      client.getFacebookFriends(completion: { friends in
        subscriber.onNext(friends)
        subscriber.onCompleted()
      })
      return Disposables.create()

onmyway133

override func viewDidLoad() {
  super.viewDidLoad()
  viewModel.friends.bind { friends in
    self.friendsCountLabel.text = "\(friends.count)"
  }
}

onmyway133

class ViewModel {
  let friends = Binding<[User]>(value: [])
  init() {
    getFacebookFriends {
      friends.value = $0
    }
  }
  func getFacebookFriends(completion: ([User]) -> Void) {
  	// Do the work
  }

onmyway133

class Binding<T> {
  var value: T {
    didSet {
      listener?(value)
    }
  }
  private var listener: ((T) -> Void)?
  init(value: T) {
    self.value = value
  }

onmyway133

class ViewModel {
  func getFacebookFriends(completion: [User] -> Void) {
    let client = APIClient()
    client.getFacebookFriends(for: user) { friends in
      DispatchQueue.main.async {
        completion(friends)
      }
    }
  }
}

onmyway133

viewModel.getFacebookFriends { friends in
  self.friendCountLabel.text = "\(friends.count)"
}

onmyway133

class ProfileController: UIViewController {
  override func viewDidLoad() {
    super.viewDidLoad()
    let viewModel = ViewModel(user: user)
    nameLabel.text = viewModel.name
    birthdayLabel.text = viewModel.birthdayString
    salaryLabel.text = viewModel.salary
    piLabel.text = viewModel.millionthDigitOfPi
  }
}