Value types are at the core of Swift (seriously, mostly everything in the Swift standard library is a value type). But how do you avoid subclassing? That's where the power of Protocol-Oriented programming comes in. Learn how to structure your code to (almost) never subclass again! Practical everyday examples and ideas for your own code base will be included.

1. @NatashaTheRobot

2. Protocol-Oriented Programming in Swift
Dave Abrahams Professor of Blowing-Your-Mind

3. –- Professor of Blowing-Your-Mind
"Swift Is a Protocol-Oriented Programming Language"

5. Practical POP
• View
• (UITable)ViewController
• Networking

6. POP Views

9. // FoodImageView.swift
import UIKit
class FoodImageView: UIImageView {
func shake() {
let animation = CABasicAnimation(keyPath: "position")
animation.duration = 0.05
animation.repeatCount = 5
animation.autoreverses = true
animation.fromValue = NSValue(CGPoint: CGPointMake(self.center.x - 4.0, self.center.y))
animation.toValue = NSValue(CGPoint: CGPointMake(self.center.x + 4.0, self.center.y))
layer.addAnimation(animation, forKey: "position")
}
}

10. // ViewController.swift
import UIKit
class ViewController: UIViewController {
@IBOutlet weak var foodImageView: FoodImageView!
@IBAction func onShakeButtonTap(sender: AnyObject) {
foodImageView.shake()
}
}

11. 💃💃💃

13. // ShakeableButton.swift
import UIKit
class ActionButton: UIButton {
func shake() {
let animation = CABasicAnimation(keyPath: "position")
animation.duration = 0.05
animation.repeatCount = 5
animation.autoreverses = true
animation.fromValue = NSValue(CGPoint: CGPointMake(self.center.x - 4.0, self.center.y))
animation.toValue = NSValue(CGPoint: CGPointMake(self.center.x + 4.0, self.center.y))
layer.addAnimation(animation, forKey: "position")
}
}

14. // ViewController.swift
class ViewController: UIViewController {
@IBOutlet weak var foodImageView: FoodImageView!
@IBOutlet weak var actionButton: ActionButton!
@IBAction func onShakeButtonTap(sender: AnyObject) {
foodImageView.shake()
actionButton.shake()
}
}

15. 🤔

16. // UIViewExtension.swift
import UIKit
extension UIView {
func shake() {
let animation = CABasicAnimation(keyPath: "position")
animation.duration = 0.05
animation.repeatCount = 5
animation.autoreverses = true
animation.fromValue = NSValue(CGPoint: CGPointMake(self.center.x - 4.0, self.center.y))
animation.toValue = NSValue(CGPoint: CGPointMake(self.center.x + 4.0, self.center.y))
layer.addAnimation(animation, forKey: "position")
}
}

17. class FoodImageView: UIImageView {
// other customization here
}
class ActionButton: UIButton {
// other customization here
}
class ViewController: UIViewController {
@IBOutlet weak var foodImageView: FoodImageView!
@IBOutlet weak var actionButton: ActionButton!
@IBAction func onShakeButtonTap(sender: AnyObject) {
foodImageView.shake()
actionButton.shake()
}
}

19. // Shakeable.swift
import UIKit
protocol Shakeable { }
extension Shakeable where Self: UIView {
func shake() {
// implementation code
}
}

20. class FoodImageView: UIImageView, Shakeable {
}
class ActionButton: UIButton, Shakeable {
}

21. class FoodImageView: UIImageView, Shakeable, Dimmable {
}

22. class FoodImageView: UIImageView, Dimmable {
}

23. Transparent View Controllers
and Dim Backgrounds
totem.training

24. 👯👯👯👯👯

25. POP (UITable)ViewControllers

27. // FoodLaLaViewController
override func viewDidLoad() {
super.viewDidLoad()
let foodCellNib = UINib(nibName: "FoodTableViewCell", bundle: nil)
tableView.registerNib(foodCellNib,
forCellReuseIdentifier: "FoodTableViewCell")
}

28. let foodCellNib = UINib(nibName: String(FoodTableViewCell), bundle: nil)
tableView.registerNib(foodCellNib,
forCellReuseIdentifier: String(FoodTableViewCell))

29. protocol ReusableView: class {}
extension ReusableView where Self: UIView {
static var reuseIdentifier: String {
return String(self)
}
}

30. extension UITableViewCell: ReusableView { }
FoodTableViewCell.reuseIdentifier
// FoodTableViewCell

31. let foodCellNib = UINib(nibName: "FoodTableViewCell",
bundle: nil)
tableView.registerNib(foodCellNib,
forCellReuseIdentifier: FoodTableViewCell.reuseIdentifier)

32. protocol NibLoadableView: class { }
extension NibLoadableView where Self: UIView {
static var nibName: String {
return String(self)
}
}

33. extension FoodTableViewCell: NibLoadableView { }
FoodTableViewCell.nibName
// "FoodTableViewCell"

34. let foodCellNib = UINib(nibName: FoodTableViewCell.nibName, bundle: nil)
tableView.registerNib(foodCellNib,
forCellReuseIdentifier: FoodTableViewCell.reuseIdentifier)

35. extension UITableView {
func register<T: UITableViewCell where T: ReusableView, T: NibLoadableView>(_: T.Type) {
let nib = UINib(nibName: T.nibName, bundle: nil)
registerNib(nib, forCellReuseIdentifier: T.reuseIdentifier)
}
}

36. let foodCellNib = UINib(nibName: "FoodTableViewCell", bundle: nil)
tableView.registerNib(foodCellNib,
forCellReuseIdentifier: "FoodTableViewCell")

37. tableView.register(FoodTableViewCell)

38. extension UITableView {
func dequeueReusableCell<T: UITableViewCell where T: ReusableView>(forIndexPath indexPath: NSIndexPath) -> T {
guard let cell = dequeueReusableCellWithIdentifier(T.reuseIdentifier, forIndexPath: indexPath) as? T else {
fatalError("Could not dequeue cell with identifier: (T.reuseIdentifier)")
}
return cell
}
}

39. guard let cell = tableView.dequeueReusableCellWithIdentifier(“FoodTableViewCell", forIndexPath: indexPath)
as? FoodTableViewCell
else {
fatalError("Could not dequeue cell with identifier: FoodTableViewCell")
}

40. let cell = tableView.dequeueReusableCell(forIndexPath: indexPath) as FoodTableViewCell

41. if indexPath.row == 0 {
return tableView.dequeueReusableCell(forIndexPath: indexPath) as DesertTableViewCell
}
return tableView.dequeueReusableCell(forIndexPath: indexPath) as FoodTableViewCell

42. iOS Cell Registration & Reusing with
Swift Protocol Extensions and
Generics
medium.com/@gonzalezreal

43. Protocol-Oriented Segue
Identifiers in Swift
natashatherobot.com

45. POP Networking

46. struct FoodService {
func get(completionHandler: Result<[Food]> -> Void) {
// make asynchronous API call
// and return appropriate result
}
}

47. enum Result<T> {
case Success(T)
case Failure(ErrorType)
}

48. struct FoodService {
func get(completionHandler: Result<[Food]> -> Void) {
// make asynchronous API call
// and return appropriate result
}
}

49. // FoodLaLaViewController
var dataSource = [Food]() {
didSet {
tableView.reloadData()
}
}
override func viewDidLoad() {
super.viewDidLoad()
getFood()
}
private func getFood() {
FoodService().getFood() { [weak self] result in
switch result {
case .Success(let food):
self?.dataSource = food
case .Failure(let error):
self?.showError(error)
}
}
}

50. View Controller Tests?!!! 😱

51. // FoodLaLaViewController
var dataSource = [Food]() {
didSet {
tableView.reloadData()
}
}
override func viewDidLoad() {
super.viewDidLoad()
getFood()
}
private func getFood() {
FoodService().getFood() { [weak self] result in
switch result {
case .Success(let food):
self?.dataSource = food
case .Failure(let error):
self?.showError(error)
}
}
}

52. // FoodLaLaViewController
func getFood(fromService service: FoodService) {
service.getFood() { [weak self] result in
// handle result
}
}

53. // FoodLaLaViewControllerTests
func testFetchFood() {
viewController.getFood(fromService: FoodService())
// 🤔 now what?
}

54. struct FoodService {
func get(completionHandler: Result<[Food]> -> Void) {
// make asynchronous API call
// and return appropriate result
}
}

55. protocol Gettable {
associatedtype T
func get(completionHandler: Result<T> -> Void)
}

56. struct FoodService: Gettable {
func get(completionHandler: Result<[Food]> -> Void) {
// make asynchronous API call
// and return appropriate result
}
}

57. // FoodLaLaViewController
override func viewDidLoad() {
super.viewDidLoad()
getFood(fromService: FoodService())
}
func getFood<S: Gettable where S.T == [Food]>(fromService service: S) {
service.get() { [weak self] result in
switch result {
case .Success(let food):
self?.dataSource = food
case .Failure(let error):
self?.showError(error)
}
}
}

58. // FoodLaLaViewControllerTests
class Fake_FoodService: Gettable {
var getWasCalled = false
func get(completionHandler: Result<[Food]> -> Void) {
getWasCalled = true
completionHandler(Result.Success(food))
}
}

59. // FoodLaLaViewControllerTests
func testFetchFood() {
let fakeFoodService = Fake_FoodService()
viewController.getFood(fromService: fakeFoodService)
XCTAssertTrue(fakeFoodService.getWasCalled)
XCTAssertEqual(viewController.dataSource.count, food.count)
XCTAssertEqual(viewController.dataSource, food)
}

60. Update: View Controller Data
Injection with Storyboards and
Segues in Swift
natashatherobot.com

61. Protocols with Associated Types
Alexis Gallagher
2015.funswiftconf.com

62. 😎😎😎

63. Practical POP
• View
• (UITable)ViewController
• Networking

64. Beyond Crusty: Real-World
Protocols
Rob Napier
thedotpost.com

65. Blending Cultures: The Best of
Functional, Protocol-Oriented, and
Object-Oriented Programming
Daniel Steinberg
realm.io

66. @NatashaTheRobot