Refactor your way forward
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The document outlines a strategic approach to refactoring a legacy iOS application suffering from outdated code and lack of tests, emphasizing the importance of incremental changes and maintaining functionality. It presents a structured method for enhancing the app's architecture using clean design principles and introduces dependency injection while gradually adding tests. Key tactics include committing frequently, organizing code effectively, and ensuring any new features are implemented without disrupting existing functionality.
![#AdvArchMobile
Cheat to provide
dependencies
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
// DONE: Invoke presenter configure(cell:forRow:)
UITableViewCell *cell = [tableView
dequeueReusableCellWithIdentifier:@"cell" forIndexPath:indexPath];
// TODO: In the new view replace with the actual cell
[self.presenter configureWithCell:[[ActionTableViewCell alloc]
init] atRow:indexPath.row];
cell.textLabel.text = self.actions[indexPath.row][0][@"Title"];
cell.detailTextLabel.text = self.actions[indexPath.row][1]
[@"Type"];
cell.imageView.image = [UIImage
imageNamed:self.actions[indexPath.row][1][@"Type"]];
return cell;
}](https://image.slidesharecdn.com/20171005refactoryourwayforward-mobilera-171023173132/85/Refactor-your-way-forward-47-320.jpg)
![#AdvArchMobile
- (void)viewDidLoad {
[super viewDidLoad];
[self.presenter viewReady];
// …
self.actions = [self
fetchActions];
// …
}
- (NSMutableArray *) fetchActions
{
return [[NSMutableArray alloc]
initWithArray:[[NSUserDefaults
standardUserDefaults]
objectForKey:@"actions"]];
}
Extract Methods with
Persistence
- (void)viewDidLoad {
[super viewDidLoad];
[self.presenter
viewReady];
// …
self.actions =
[[NSMutableArray alloc]
initWithArray:
[[NSUserDefaults
standardUserDefaults]
objectForKey:@"actions"]];
// …
}](https://image.slidesharecdn.com/20171005refactoryourwayforward-mobilera-171023173132/85/Refactor-your-way-forward-50-320.jpg)
Refactor your way forward
- 1. Refactor Your Way Forward Jorge D. Ortiz-Fuentes @jdortiz
- 3. #AdvArchMobile Agenda ★ The challenge ★ Strategy ★ Tactics ★ Recap
- 5. #AdvArchMobile Sounds familiar? ★ Legacy application • No tests • Outdated ★ Written in Objective-C ★ Not (m)any tests ★ Multiple styles and ways to do things ★ Not much info from the previous developer
- 6. #AdvArchMobile Need a Better Architecture ★ Difficult to add new features without breaking existing ones ★ Difficult to find and solve bugs ★ Expensive to maintain ★ Difficult to add tests
- 7. #AdvArchMobile My Example ★ App: OpenIt ★ Credit: Patrick Balestra ★ Thanks! ★ Great code for an example ★ All criticism IS constructive
- 8. Strategy
- 10. Persistance FW View Network LocationFW Presenter Entity Gateway Clean Architecture Interactor Entity
- 11. Clean Architecture: iOS App Delegate View (VC) Presenter Interactor Entity Gateway Connector
- 12. #AdvArchMobile Goals ★ New feature: Apple rating API ★ Don’t break anything ★ Enhance when possible
- 13. No Big Bang Rewrite Still love the TV series
- 15. – Sun Tzu “Know your enemy and know yourself and you can fight a hundred battles without disaster.”
- 17. #AdvArchMobile Make it Work ★ Install dependencies • Pods/Carthage, if any • API keys ★ Build ★ Fix big problems until it works
- 18. #AdvArchMobile Make it Work ★ DON’T update the project settings yet ★ DON’T add any functionality yet ★ DON’T fix any other bugs yet
- 19. Commit!
- 20. #AdvArchMobile Explore the Battlefield ★ Take a glimpse a the code ★ Tests? Runnable? Pass? ★ Documentation? ★ Oral transmission? ★ Business goals
- 21. #AdvArchMobile Design your strategy ★ Planed features ★ Pain points
- 22. #AdvArchMobile Main Strategic Approaches ★ From the model upwards • Less intuitive • Still requires injections from top to bottom ★ From the views inwards • More work initially
- 23. #AdvArchMobile Shape the Strategy ★ App delegate: Size? Relevant tasks? Easy to replace (And remove main.m)? ★ Storyboards? ★ Tests coverage? Only for the model? ★ Frameworks used (Persistence & others)? ★ DI? Abstractions for DIP? ★ VCs screaming for changes?
- 24. But remember Only small non breaking changes allowed
- 25. Tactics
- 26. Add Tests
- 27. #AdvArchMobile Add Tests ★ Set up the testing target ★ Language is Swift ★ Start with main target ★ Don't add others (frameworks) until required ★ Cmd+U To test that it works. ★ Delete the default tests
- 28. Commit!
- 29. Zero Visibility Here Be Dragons
- 30. Use the Tools
- 31. #AdvArchMobile Proper Git ★ Branch often ★ Better, git flow: Feature branch for each part of migration ★ Avoid long lived branches ★ Use branch by abstraction instead
- 32. #AdvArchMobile Branch by Abstraction 2 1 1 1 2
- 33. #AdvArchMobile Use Xcode Groups ★ Put all legacy code in a group ★ Support files and assets in another one ★ Create new Groups (or folders) to organize new code
- 35. 😂
- 36. Replace App Delegate (& main.m)
- 37. #AdvArchMobile Very Simple (when it is) @UIApplicationMain class AppDelegate: UIResponder, UIApplicationDelegate { }
- 38. Commit!
- 40. #AdvArchMobile Introduce DI from Root VC ★ Change behavior in Info.plist ★ App delegate creates initial view controller ★ Pass into a dumb (yet) connector ★ Add Bridging header
- 42. Commit!
- 43. View Controller Talks to Dumb Presenter
- 45. #AdvArchMobile Introduce Presenter ★ @objc ★ Pass events ★ Test VC ★ Generate a skeleton for the presenter
- 46. #AdvArchMobile Cheat to keep it working - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { // DONE: Invoke presenter numberOfActions NSInteger rows = self.presenter.numberOfActions; // TODO: Remove when using real presenter if (rows < 0) { rows = self.actions.count; } return rows; }
- 47. #AdvArchMobile Cheat to provide dependencies - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { // DONE: Invoke presenter configure(cell:forRow:) UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell" forIndexPath:indexPath]; // TODO: In the new view replace with the actual cell [self.presenter configureWithCell:[[ActionTableViewCell alloc] init] atRow:indexPath.row]; cell.textLabel.text = self.actions[indexPath.row][0][@"Title"]; cell.detailTextLabel.text = self.actions[indexPath.row][1] [@"Type"]; cell.imageView.image = [UIImage imageNamed:self.actions[indexPath.row][1][@"Type"]]; return cell; }
- 48. Commit!
- 50. #AdvArchMobile - (void)viewDidLoad { [super viewDidLoad]; [self.presenter viewReady]; // … self.actions = [self fetchActions]; // … } - (NSMutableArray *) fetchActions { return [[NSMutableArray alloc] initWithArray:[[NSUserDefaults standardUserDefaults] objectForKey:@"actions"]]; } Extract Methods with Persistence - (void)viewDidLoad { [super viewDidLoad]; [self.presenter viewReady]; // … self.actions = [[NSMutableArray alloc] initWithArray: [[NSUserDefaults standardUserDefaults] objectForKey:@"actions"]]; // … }
- 51. #AdvArchMobile And Test It func testFetchActionsObtainsDataFromUserDefaults() { let userDefaultsMock = UserDefaultsMock() sut.setValue(userDefaultsMock, forKey: "userDefaults") _ = sut.fetchActions() XCTAssertTrue(userDefaultsMock.objectForKeyInvoked) }
- 52. Commit!
- 53. Get the new VC in
- 54. #AdvArchMobile New Swift VC ★ Replaces the old one ★ Refactor Storyboard ★ New Swift class with the desired name ★ Reuse the tests to create an instance of this one
- 57. #AdvArchMobile Rough Edges ★ Structs & Enums ★ Tuples ★ Generics ★ Curried & global functions ★ Typealiases
- 58. #AdvArchMobile @objcMembers class ActionWrapper: NSObject { private var action: Action var title: String { get { return action.title } set(newTitle) { action.title = newTitle } } //… init(action: Action) { self.action = action } init(title: String, type: String, url: String) { action = Action(title: title, type: type, url: url) } } Use Wrappers struct Action { var title: String var type: String var url: String }
- 59. Commit!
- 60. #AdvArchMobile But… ★ Entity Gateway should implement both ★ Value semantics are lost ★ Use scarcely ★ Remove when possible
- 61. And Finally… New Use Case
- 62. #AdvArchMobile Use Case typealias AskForRatingCompletion = (Bool) -> () class AskForRatingUseCase: UseCase { let entityGateway: EntityGateway let preferencesGateway: PreferencesGateway let completion: AskForRatingCompletion init(entityGateway: EntityGateway, preferencesGateway: PreferencesGateway, completion: @escaping AskForRatingCompletion) { self.entityGateway = entityGateway self.preferencesGateway = preferencesGateway self.completion = completion } func execute() { let ask = entityGateway.numberOfActions > 10 && preferencesGateway.daysSinceLastRating > 180 completion(ask) } }
- 63. #AdvArchMobile // View (extension) func askForRating() { SKStoreReviewController.requestRe view() } Presenter & View // Presenter func viewReady() { actions = fetchActions() mayAskUserForRating() } private func mayAskUserForRating() { let useCase = useCaseFactory.askForRatingUseCas e(completion: { (shouldAsk: Bool) in view.askForRating() }) useCase.execute() }
- 64. Commit!
- 65. Recap
- 66. #AdvArchMobile Recap ★ Incremental refactoring is feasible ★ Design your strategy ★ Use the tactics ★ Small non breaking changes are best ★ Tests are key ★ Don’t follow sequential order
- 67. Tusen Takk!
- 68. Thank You!