Protocols and The Promised Land Take 2

try! Swift edition

Transcript

1. Protocols and the Promised Land @MicheleTitolo
2. Swift is shiny! And new!
3. Swift is not Objective-C
4. Interop
5. as? as? as?
6. as? lies
7. let vendor = ObjcObject() let items = vendor.giveMeItems() as? [Fruit]
8. let vendor = ObjcObject() let items = vendor.giveMeItems().map { $0 as Fruit }
9. @objc spreads like a virus
10. @objc protocol SomeProtocol { func someFunc() } class MyClass: SomeProtocol {}
11. @objc protocol SomeProtocol { func someFunc() } @objc class MyClass: NSObject, SomeProtocol {}
12. Swift > Objc > Swift
13. Can’t #import “MyApp-Swift.h” in header
14. Can’t conform, can’t subclass
15. Bridging
16. many parts of Swift don’t bridge
17. Does this really need to be used in Objective-C?
18. framework headers can’t be in bridging header
19. use @import
20. Partial bridging
21. -Swift.h will leave out funcs/vars that don’t bridge
22. Again: does this really need to be bridged?
23. Type System
24. properties can have 1 type
25. protocol Themeable {} class ListViewController: UIViewController, Themeable {} var themedViewController: // UIViewController, Themeable ????
26. two workarounds
27. public protocol ViewControllerProtocol { var view: UIView! { get } var storyboard: UIStoryboard? { get } init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) func viewDidLoad() // etc } protocol ThemeableViewController: Themeable, ViewControllerProtocol {} var themedViewController: ThemeableViewController Swift-y but hack-y
28. var themed: Themeable { get { return self.viewController as! Themeable } set(newThemeable) { if let themedViewController = newThemeable as? UIViewController{ viewController = themedViewController } } } var viewController: UIViewController init<T where T: Themeable, T: UIViewController>(viewController: T) { self.viewController = viewController } Also swfit-y also hack-y
29. Can’t override type with inheritance
30. Deep object hierarchies
31. Protocols
32. Composition instead of inheritance
33. Protocols and inheritance don’t mix
34. use POP to mock
35. Generics
36. Can’t reference a generic protocol
37. protocol Holder { typealias Item var items: [Item] { get } } class Basket<Thing>: Holder{ var items: [Thing] = [] func add(item: Thing) { items.append(item) } }
38. var someHolder: Holder var someBasket: Basket
39. var someHolder: Holder<Peach> var someBasket: Basket<Peach>
40. Covariance only works with generic classes
41. Covariance: If a Cat is an Animal func feed(animal: Animal) can receive a Cat
42. typealias Object typealias Object: String typealias RoundObject: Object
43. generic classes can specify type requirements
44. class Basket<Thing: Fruit> { var items: [Thing] = [] func add(item: Thing) { items.append(item) } }
45. class Basket<Thing: Fruit> { var items: [Thing] = [] func add(item: Thing) { items.append(item) } } class FruitBasket: Basket<Fruit> {} class PeachBasket: FruitBasket<Peach> {}
46. class Bag<Stuff> { class Basket<Thing: Stuff> { var items: [Thing] = [] func add(item: Thing) { items.append(item) } } }
47. Generic non-NSObjects have issues
48. Explicitly call out class for now
49. Swift introduces awesome new patterns
50. Thanks! @MicheleTitolo
51. Photo Credits • https://www.flickr.com/photos/83073191@N00/21709516808/ • https://www.flickr.com/photos/64181484@N04/21946459678/ • https://www.flickr.com/photos/66904032@N05/18905223864/ • https://www.flickr.com/photos/27454212@N00/22120629112/ • https://www.flickr.com/photos/8725928@N02/24439195435/ • https://www.flickr.com/photos/28480761@N04/24143685631/