99 Problems, but MVC ain't one

- Many iOS apps suffer from the Massive View Controller (MVC) anti-pattern.
- The poor, overworked UIViewController becomes bloated with business logic, model data transformation, user input processing, view layout, data source and delegate code.
- This leads to apps that are difficult to extend, maintain and test.
- This talk will explore a number of different architectural approaches that can help address this problem.
- It will also highlight some options for data binding mechanisms you can use in Objective-C and Swift apps.

Transcript

1. 99 PROBLEMS BUT MVC AIN'T ONE
2. WHAT IS MVC ? MVC AS IOS ANTIPATTERN ARCHITECTURAL ALTERNATIVES DATA BINDING
3. MODEL-VIEW-CONTROLLER THE ! AND " OF ARCHITECTURAL PATTERNS
4. MODEL-VIEW-CONTROLLER DEFINES NOT ONLY THE ROLES OBJECTS PLAY IN THE APPLICATION, IT DEFINES THE WAY OBJECTS COMMUNICATE WITH EACH OTHER. EACH OF THE THREE TYPES OF OBJECTS IS SEPARATED FROM THE OTHERS BY ABSTRACT BOUNDARIES AND COMMUNICATES WITH OBJECTS OF THE OTHER TYPES ACROSS THOSE BOUNDARIES. DEVELOPER.APPLE.COM
5. MVC (EMOJIFIED)
6. MVC AS IOS ANTIPATTERN #1. UIVIEWCONTROLLERS UNDERMINE THE SEPARATION OF ROLES & BLUR BOUNDARIES
7. AS A RESULT BAD THINGS CAN HAPPEN...
9. COME AT ME BRO
10. MVC AS IOS ANTIPATTERN #2. UIVIEWCONTROLLERS ASSUME TOO MANY RESPONSIBILITIES WHICH OFTEN LEADS TO CODE BLOAT
11. Layout & view hierarchy management View lifecyle presentation logic Model data transformation Delegate protocol conformance User interaction handling & validation
12. MVC AS IOS ANTIPATTERN #3. MASSIVE VIEW CONTROLLERS (MVC) ARE HARD TO TEST ADEQUATELY AND THUS BECOME EXPENSIVE TO MAINTAIN & EXTEND
13. WHAT CAN YOU DO ?
15. ARCHITECTURAL ALTERNATIVES
16. #1. GO THIN OR GO HOME
17. THIN PLEASE ! OPT FOR THINNER VIEW CONTROLLERS DECOUPLE RESPONSIBILITIES INTO INDIVIDUALLY COMPOSABLE COMPONENTS
18. #2. MVVM: MODEL-VIEW-VIEWMODEL
19. MVVM (EMOJIFIED)
21. #BROMANCE
22. VIEW --> VIEWMODEL --> MODEL
23. BETTER SEPARATION OF CONCERNS LOOSER COUPLING OF COMPONENTS PLATFORM AGNOSTIC VIEWMODELS ARE PONSOS OR SWIFT VALUE TYPES == EASY TO UNIT TEST
24. DATA BINDING THE SECRET SAUCE OF MVVM
25. FACILITATES TWO-WAY COMMUNICATION BETWEEN THE VIEW & THE VIEWMODEL WITHOUT BREAKING THE MVVM ROLE ABSTRACTION
26. NATIVE IOS OPTIONS : KVO, NOTIFICATIONS, DELEGATES
27. KVO LIFESPAN DEPENDENCIES, TIGHTER COUPLING, LOTS OF BOILERPLATE
28. NOTIFICATIONS ONE-WAY COMMUNICATION, BROADCAST MODE, OBSERVER CLEAN-UP
29. DELEGATES ENFORCES STRONGER ONE-TO-ONE RELATIONSHIP BETWEEN VIEW & VIEWMODEL
30. REACTIVECOCOA
31. FUNCTIONAL REACTIVE PROGRAMMING SIGNALS : A STREAM OF EVENTS OVER TIME HIGHER ORDER FUNCTIONS : COMBINE, MAP, FILTER CONVENIENCE BINDINGS FOR UIKIT ELEMENTS
32. MODEL @interface EmojiMonster: NSObject @property (strong,nonatomic) NSString *name; @property (strong,nonatomic) NSString *fightingName; @property (strong,nonatomic) NSNumber *intelligenceLevel; @property (strong,nonatomic) NSNumber *fightingPowerLevel; @property (strong,nonatomic) NSNumber *battlesFought; @end
33. VIEWMODEL @interface EmojiMonsterViewModel: NSObject @property (strong,nonatomic) NSString *name; @property (strong,nonatomic) NSString *fightingName; @property (strong,nonatomic) NSString *intelligence; @property (strong,nonatomic) NSString *fightingPower; @property (strong,nonatomic) NSString *battles; @property (strong,nonatomic) id<ModelServices> modelServices; @end
34. VIEW @interface EmojiMonsterViewController: UIViewController @property (weak,nonatomic) IBOutlet UILabel *monsterNameLabel; @property (weak,nonatomic) IBOutlet UILabel *intelligenceLabel; @property (weak,nonatomic) IBOutlet UILabel *fightingPowerLabel; @property (weak,nonatomic) IBOutlet UILabel *monsterNameLabel; @property (weak,nonatomic) IBOutlet UILabel *battlesLabel; @property (strong,nonatomic) EmojiMonsterViewModel *viewModel; @end
35. VIEW - SIMPLE PROPERTY BINDING RAC(self.intelligenceLabel, text) = RACObserve(self, viewModel.intelligence);
36. VIEW - IGNORING NIL VALUES [RACObserve(self, viewModel.intelligence) ignore:nil];
37. VIEW - ONLY NOTIFY CHANGES [[RACObserve(self, viewModel.intelligence) ignore:nil] distinctUntilChanged];
38. VIEW - THREAD MARSHALLING [[[RACObserve(self, viewModel.intelligence) ignore:nil] distinctUntilChanged] deliverOn:[RACScheduler mainThreadScheduler]];
39. VIEW - SIGNAL FILTERING [[[RACObserve(self, viewModel.name) ignore:nil] distinctUntilChanged] filter:^(NSString *newName){ return [newName hasPrefix@"Z"]; }];
40. VIEW - UIKIT BUILT-IN BINDINGS [self.battlesLabel.rac_textSignal subscribeNext:^(NSString *newValue){ NSLog(@"Got new battle value : %@", newValue); }];
41. VIEW - SIGNAL FROM VIEWMODEL PROPERTY RACSignal *nameSignal = [[RACObserve(self, viewModel.name) ignore:nil] distinctUntilChanged] deliverOn:[RACScheduler mainThreadScheduler]];
42. VIEW - SIGNAL FROM VIEWMODEL PROPERTY RACSignal *fightingNameSignal = [[RACObserve(self, viewModel.fightingName) ignore:nil] distinctUntilChanged] deliverOn:[RACScheduler mainThreadScheduler]];
43. VIEW - COMBINED SIGNALS [RACSignal combineLatest:@[nameSignal,fightingNameSignal] reduce:^(NSString *name, NSString *fightName){ return [NSString stringWithFormat:@"%@ %@", name, fightName]; }];
44. VIEW - AVOID RETAIN CYCLES #import "RACEXTScope.h" @weakify(self); [[[RACObserve(self, viewModel.battles) ignore:nil] distinctUntilChanged] subscribeNext:^(NSString *newValue){ @strongify(self); self.battlesLabel.text = newValue; }];
45. VIEWMODEL - BIND UI ACTIONS TO COMMANDS [[RACCommand alloc] initWithSignalBlock:^RACSignal *(id input) { return [[[self refreshSignal:input] ignore:nil] deliverOn:[RACScheduler mainThreadScheduler]]; }];
46. VIEW - BIND UI ANIMATIONS TO VIEWMODEL REFRESHES RACSignal *viewModelRefreshSignal = self.viewModel.executeRefresh.executing; [viewModelRefreshSignal subscribeNext:^(NSNumber *x) { @strongify(self); if (x.boolValue) { [self animateActivity]; } else { [self stopAnimateActivity]; } }];
47. PROS CONCISE, FLEXIBLE, POWERFUL MVVM SUPPORT BAKED IN CROSS PLATFORM
48. CONS EXTERNAL OSS DEPENDENCY FRP LEARNING CURVE OBJC FOCUS
49. SWIFT BINDING
50. PROPERTY OBSERVERS GENERICS CLOSURES
52. HOLY SHET ! WE TOTALLY ❤ SWIFT'S BUILT-IN PROPERTY OBSERVERS
53. PROPERTY OBSERVERS struct EmojiMonster { var name: String { didSet { println("Bow before the mighty \(name) underlings !") } } init(_ name: String){ self.name = name } }
54. STANDARD LIBRARY TYPE WRAPPING struct BindableString { var value: String { didSet { // invoke some useful logic here } } init(_ v: String){ value = v } }
55. DEFINE A LISTENER typealias Listener = String -> Void var listener: Listener? func bind(listener: Listener?){ self.listener = listener listener?(value) } var value: String { didSet { listener?(value) } }
56. GENERIC BINDABLE struct Bindable<T> { typealias Listener = T -> Void var listener: Listener? var value: T { didSet { listener?(value) } } init(_ v: T){ value = v } }
57. BINDING A CLOSURE let name = Bindable("Tiddles") let fightingName = Bindable("The Dark Destroyer") let nameLabel = UILabel() let fightingNameLabel = UILabel() name.bind { nameLabel.text = $0 } fightingName.bind { fightingNameLabel.text = $0 }
58. MVVM VIEWMODEL PROTOCOL protocol EmojiViewModel { var name : Bindable<String> { get } }
59. MVVM VIEWMODEL IMPLEMENTATION struct EmojiMonsterViewModel: EmojiViewModel { let name : Bindable<String> let monster : EmojiMonster init(_ emoji: EmojiMonster){ self.monster = emoji self.name = monster.name } }
60. MVVM VIEW BIND VIEWMODEL class EmojiMonsterViewController { var nameLabel: UILabel var viewModel: EmojiViewModel { didSet { viewModel.name.bind { [unowned self] in self.nameLabel.text = $0 } } } }
61. TAKEAWAYS DECOMPOSE MASSIVE VIEWCONTROLLERS MVVM FOR STRUCTURE & EASIER TESTING EXPLORE RAC OR SWIFT FOR DATA BINDING
62. RESOURCES OBJC.IO BLOG.SCOTTLOGIC.COM/CEBERHARDT ASHFURROW.COM GITHUB.COM/REACTIVECOCOA RASIC.INFO