Originally presented at Auckland iOS meetup http://www.meetup.com/auckland-ios-meetup/events/227283431/

1. P!MVVM@NATASHATHEROBOT

4. "Swift Is a Protocol-Oriented
Programming Language"
— Dave Abrahams, Professor of Blowing-Your-Mind

5. UITableViewDelegate
UITableViewDataSource
UITextFieldDelegate
NSURLSessionDelegate
CLLocationManagerDelegate
MCSessionDelegate

6. !

7. !

8. !

9. !

10. Artsy Engineering: MVVM in Swift

11. MODEL
let amount = 6729383.99

12. VIEW
Your balance is $6,729,383.99

13. VIEWMODEL
struct AccountViewModel {
let displayBalance: String
init(model: BankAccount) {
let formattedBalance = model.balance.currencyValue
displayBalance = "Your balance is (formattedBalance)"
}
}

14. VIEWCONTROLLER
var viewModel = ViewModel(model: Account)

18. VIEWCONTROLLER
var viewModel = ViewModel(model: Account)

19. PROTOCOLS
!!!

21. THE PROBLEM
class SwitchWithTextTableViewCell: UITableViewCell {
func configure(
title: String,
titleFont: UIFont,
titleColor: UIColor,
switchOn: Bool,
switchColor: UIColor = .purpleColor(),
onSwitchToggleHandler: onSwitchToggleHandlerType? = nil)
{
// configure views here
}
}

22. PROTOCOLS TO
THE RESCUE !

23. protocol SwitchWithTextCellProtocol {
var title: String { get }
var titleFont: UIFont { get }
var titleColor: UIColor { get }
var switchOn: Bool { get }
var switchColor: UIColor { get }
func onSwitchTogleOn(on: Bool)
}

24. extension SwitchWithTextCellProtocol {
var switchColor: UIColor {
return .purpleColor()
}
}

25. class SwitchWithTextTableViewCell: UITableViewCell {
func configure(withDelegate delegate: SwitchWithTextCellProtocol)
{
// configure views here
}
}

26. struct MinionModeViewModel: SwitchWithTextCellProtocol {
var title = "Minion Mode!!!"
var switchOn = true
var switchColor: UIColor {
return .yellowColor()
}
func onSwitchTogleOn(on: Bool) {
if on {
print("The Minions are here to stay!")
} else {
print("The Minions went out to play!")
}
}
}

27. CELLFORROWATINDEXPATH
// YourViewController.swift
let cell = tableView.dequeueReusableCellWithIdentifier("SwitchWithTextTableViewCell",
forIndexPath: indexPath) as! SwitchWithTextTableViewCell
// this is where the magic happens!
cell.configure(withDelegate: MinionModeViewModel())
return cell

28. !

29. ✍

30. protocol SwitchWithTextCellDataSource {
var title: String { get }
var switchOn: Bool { get }
}
protocol SwitchWithTextCellDelegate {
func onSwitchTogleOn(on: Bool)
var switchColor: UIColor { get }
var textColor: UIColor { get }
var font: UIFont { get }
}

31. // SwitchWithTextTableViewCell
func configure(withDataSource dataSource: SwitchWithTextCellDataSource,
delegate: SwitchWithTextCellDelegate?)
{
// configure views here
}

32. struct MinionModeViewModel: SwitchWithTextCellDataSource {
var title = "Minion Mode!!!"
var switchOn = true
}

33. extension MinionModeViewModel: SwitchWithTextCellDelegate {
var switchColor: UIColor {
return .yellowColor()
}
func onSwitchTogleOn(on: Bool) {
if on {
print("The Minions are here to stay!")
} else {
print("The Minions went out to play!")
}
}
}

34. // SettingsViewController
let viewModel = MinionModeViewModel()
cell.configure(withDataSource: viewModel, delegate: viewModel)
return cell

35. !

36. @MHOLLEMANS: MIXINS
AND TRAITS IN SWIFT 2.0

39. class AIPlayer: GameObject, AITrait, GunTrait, RenderTrait, HealthTrait {
...
}
class ZapMonster: GameObject, GunTrait, RenderTrait, HealthTrait, MovementTrait {
...
}

40. ! "

41. protocol TextPresentable {
var text: String { get }
var textColor: UIColor { get }
var font: UIFont { get }
}
protocol SwitchPresentable {
var switchOn: Bool { get }
var switchColor: UIColor { get }
func onSwitchTogleOn(on: Bool)
}

42. protocol ImagePresentable {
var imageName: String { get }
}
protocol TextFieldPresentable {
var placeholder: String { get }
var text: String { get }
func onTextFieldDidEndEditing(textField: UITextField)
}

43. extension TextPresentable {
var textColor: UIColor {
return .blackColor()
}
var font: UIFont {
return .systemFontOfSize(17)
}
}

44. !!!
class SwitchWithTextTableViewCell: UITableViewCell {
func configure<T where T: TextPresentable, T: SwitchPresentable>(withPresenter presenter: T)
// configure views here
}
}

45. !!!!!!
typealias SwitchWithTextViewPresentable = protocol<TextPresentable, SwitchPresentable>
class SwitchWithTextTableViewCell: UITableViewCell {
func configure(withPresenter presenter: T)
// configure views here
}
}

46. extension MinionModeViewModel: TextPresentable {
var text: String { return "Minion Mode" }
var textColor: UIColor { return .blackColor() }
var font: UIFont { return .systemFontOfSize(17.0) }
}

47. extension MinionModeViewModel: SwitchPresentable {
var switchOn: Bool { return false }
var switchColor: UIColor { return .yellowColor() }
func onSwitchTogleOn(on: Bool) {
if on {
print("The Minions are here to stay!")
} else {
print("The Minions went out to play!")
}
}
}

48. let cell = tableView.dequeueReusableCellWithIdentifier("SwitchWithTextTableViewCell",
forIndexPath: indexPath) as! SwitchWithTextTableViewCell
let viewModel = MinionModeViewModel()
cell.configure(withPresenter: viewModel)
return cell

49. !"#

50. "Change is the only constant."
— Unknown

52. typealias SwitchWithTextViewPresentable = protocol<TextPresentable, SwitchPresentable, ImagePresentable>
class SwitchWithTextTableViewCell: UITableViewCell {
func configure(withPresenter presenter: T)
// configure views here
}
}

53. extension MinionModeViewModel: ImagePresentable {
var imageName: String { return "minionParty.png" }
}

54. !"

55. > Use Protocols to Configure Your Views
> Use Protocol Extensions for Defaults
> Use ViewModels to Provide Data for the Protocols

56. HOW CAN WE
MAKE THIS
BETTER?