Swift Code Patterns From the Ranch

At the Big Nerd Ranch we've been experimenting with Swift since it was first announced. We've also been lucky enough to have some wonderful clients whom have empowered us to use Swift on their projects. This talk will explore some of the way we've embraced Swift patterns as we interact with UIKit on our projects. We'll review some small ideas and then move up in scale to finish with some larger ideas. With luck you'll walk away with some actionable patterns to make your own Swift projects safer, easier to read and easier to test.

http://cocoaconf.com/dc-2016/sessions/Swift-Code-Patterns-From-the-Ranch

Transcript

1. Swift Code Patterns From the Ranch https://github.com/bignerdranch/RanchWeather * Built Using Swift 3, Xcode 8b6
2. June 2, 2014
3. Swift Strongly Typed Value Types Composition Protocol-Oriented Programming Objective-C / UIKit Weakly Typed Reference Types Inheritance Object-Oriented Programming
4. How do we use UIKit with Swift and honoring its goals?
5. Safe. Fast. Expressive. https://swift.org/about/
6. Safe. Expressive.
7. Safe. Expressive. Testable.
9. Initialization
10. class Car { let driver: Driver init() { } }
11. class Car { let driver: Driver init() { } // Return from initializer without // initializing all stored properties. }
12. class Car { let driver: Driver init(driver: Driver) { self.driver = driver } }
13. View Controllers
14. class DisplayViewController: UIViewController { let weatherService: WeatherService }
15. init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) init?(coder aDecoder: NSCoder)
17. class DisplayViewController: UIViewController { let weatherService: WeatherService }
18. class DisplayViewController: UIViewController { var weatherService: WeatherService? }
19. class DisplayViewController: UIViewController { var weatherService: WeatherService! }
20. Dependency Injection
21. // Injectable is a simple protocol to helps enforce Dependency Injection. // It is typically used on View Controllers where you don't have early // life-cycle access and need to inject or configure required properties // after the object has been initialized. protocol Injectable { // When honoring this protocol we expect you to make a method called // inject() that has the needed properties for this object. // checkDependencies is a method intended to verify that our // implicitly unwrapped optionals preconditions have been populated. // It should called in an early life-cycle method where the // required dependancies should have already been set. // For View Controllers, viewDidLoad() is a common choice. func checkDependencies() }
22. class WeatherDisplayViewController: UIViewController { var weatherService: WeatherService! var location: Location! override func viewDidLoad() { super.viewDidLoad() checkDependencies() updateUI() } } //MARK: - Injectable extension WeatherDisplayViewController: Injectable { func inject(weatherService: WeatherService, location: Location) { self.weatherService = weatherService self.location = location } func checkDependencies() { precondition(weatherService != nil) precondition(location != nil) } }
23. Dependency Injection
24. DRY Strings
25. extension UserDefaults { enum Key { static let themeIdentifier = "com.ranchweather.userdefaults.theme" } enum Notifications { static let themeDidChange = Notification.Name("com.ranchweather.notification.themeDidChange") } } string(forKey: Key.themeIdentifier) NotificationCenter.default.post(name: Notifications.themeDidChange, object: self)
26. extension UIImage { enum Asset: String { case clearDay = "clear-day" case clearNight = "clear-night" case rain = "rain" case snow = "snow" case sleet = "sleet" case wind = "wind" case fog = "fog" case cloudy = "cloudy" case partlyCloudyDay = "partly-cloudy-day" case partlyCloudyNight = "partly-cloudy-night" } convenience init!(asset: Asset) { self.init(named: asset.rawValue) } } UIImage(asset: .snow)
27. extension UIStoryboard { private enum File: String { case main = "Main" case weatherDisplay = "WeatherDisplay" case feedback = "Feedback" case debugMenu = "DebugMenu" } private convenience init(_ file: File) { self.init(name: file.rawValue, bundle: nil) } } let storyboard = UIStoryboard(.weatherDisplay)
28. View Controllers from Storyboards
29. extension UIStoryboard { private enum Identifier: String { ... } private convenience init(_ identifier: Identifier) { self.init(name: identifier.rawValue, bundle: nil) } } let storyboard = UIStoryboard(.WeatherDisplay)
30. extension UIStoryboard { static func weatherDisplayViewController() -> WeatherDisplayViewController { let storyboard = UIStoryboard(.weatherDisplay) return storyboard.instantiateInitialViewController() as! WeatherDisplayViewController } } let vc = UIStoryboard.weatherDisplayViewController()
32. extension UIStoryboard { static func debugViewControllerStack(configure: (DebugMenuViewController) -> Void) -> UINavigationController { let navigationController = UIStoryboard(.DebugMenu). instantiateInitialViewController() as! UINavigationController let debugMenu = navigationController.viewControllers[0] as! DebugMenuViewController configure(debugMenu) return navigationController } } let debugNavigationController = UIStoryboard.debugViewControllerStack { (debugVC) in debugVC.inject(userDefaults: UserDefaults.standard, delegate: self) } present(debugNavigationController, animated: true, completion: nil)
33. Data Adaptors (Many DataSources)
34. WeatherDetailVC
35. WeatherDetailVC WeatherService
 
 fetchWeatherReport(…)
36. WeatherDetailVC WeatherService
 
 fetchWeatherReport(…) WeatherSource
 
 fetchWeatherReport(…)
37. WeatherDetailVC WeatherService dataSource: WeatherSource WeatherSource
 
 fetchWeatherReport(…)
38. WeatherDetailVC WeatherService dataSource: WeatherSource WeatherSource
 
 fetchWeatherReport(…) ForcastIOSource
39. WeatherDetailVC WeatherService dataSource: WeatherSource WeatherSource
 
 fetchWeatherReport(…) YahooSource ForcastIOSource
40. WeatherDetailVC WeatherService dataSource: WeatherSource WeatherSource
 
 fetchWeatherReport(…) Prepared Response
42. WeatherDetailVC WeatherService dataSource: WeatherSource WeatherSource
 
 fetchWeatherReport(…) Prepared Response
43. Service Interface
44. struct WeatherService { func fetchWeatherReport(latitude: Double, longitude: Double, completion: @escaping (_ result: WeatherService.Result) -> Void) { dataSource.fetchWeatherReport(latitude: latitude, longitude: longitude, completion: completion) } }
45. struct WeatherService { enum Result { case success(WeatherReport) case failure(WeatherService.Error) } func fetchWeatherReport(latitude: Double, longitude: Double, completion: @escaping (_ result: WeatherService.Result) -> Void) { dataSource.fetchWeatherReport(latitude: latitude, longitude: longitude, completion: completion) } }
46. struct WeatherService { enum Result { case success(WeatherReport) case failure(WeatherService.Error) // Many would use ErrorType } }
47. struct WeatherService { enum Result { case success(WeatherReport) case failure(WeatherService.Error) // Many would use ErrorType } enum Error { case invalidLatitude case invalidLongitude case parseError case noPreparedResponse case networkError(NSError) case noDataError } }
48. enum ValidatorError: Equatable { case MinLengthInvalid(actual: Int, required: Int) case MaxLengthInvalid(actual: Int, allowed: Int) case RequiredCharacterMissing(requiredSet: NSCharacterSet) case RequiredPrefixCharacterMissing(requiredPrefixSet: NSCharacterSet) case DoesNotMatchRegex(regex: String) } // Taken From Swift2 project, forgive the CamelCase enum names.
49. struct WeatherService { enum Result { case success(WeatherReport) case failure(WeatherService.Error) } enum Error {} func fetchWeatherReport(latitude: Double, longitude: Double, completion: @escaping (_ result: WeatherService.Result) -> Void) { dataSource.fetchWeatherReport(latitude: latitude, longitude: longitude, completion: completion) } }
50. Theming
51. UIColor
52. private extension UIColor { convenience init(hex: UInt32) { // Note: This is called the bit shift operator let red = CGFloat((hex >> 16) & 0xff) / 255 let green = CGFloat((hex >> 8) & 0xff) / 255 let blue = CGFloat((hex ) & 0xff) / 255 self.init(red: red, green: green, blue: blue, alpha: 1) } } let yellow = UIColor(hex: 0xECB02F) // Note: These are called hexadecimal literals
53. private enum BNRColors { static let offWhite = UIColor(hex: 0xEEEEEE) static let offBlack = UIColor(hex: 0x333333) static let red = UIColor(hex: 0xE15827) static let yellow = UIColor(hex: 0xECB02F) }
54. enum Theme: String { case day = "com.ranchweather.theme.day" case night = "com.ranchweather.theme.night" var backgroundColor: UIColor { switch self { case .day: return BNRColors.offWhite case .night: return BNRColors.offBlack } } var textColor: UIColor { switch self { case .day: return BNRColors.offBlack case .night: return BNRColors.offWhite } } var tintColor: UIColor { switch self { case .day: return BNRColors.red case .night: return BNRColors.yellow } } var preferredStatusBarStyle: UIStatusBarStyle { switch self { case .day: return UIStatusBarStyle.default case .night: return UIStatusBarStyle.lightContent } } }
55. struct Themer { let theme: Theme init(theme: Theme) { self.theme = theme updateGlobalThemeSettings() } }
56. struct Themer { let theme: Theme init(theme: Theme) { self.theme = theme updateGlobalThemeSettings() } func updateGlobalThemeSettings() { updateNavigationBar() reloadWindow() } func updateNavigationBar() { let apperance = UINavigationBar.appearance() apperance.barTintColor = theme.backgroundColor apperance.titleTextAttributes = [NSForegroundColorAttributeName: theme.textColor] apperance.tintColor = theme.tintColor }
57. struct Themer { ... // Manual calls func theme(_ tableView: UITableView) { tableView.backgroundColor = theme.tableViewBackgroundColor } func theme(_ cell: UITableViewCell) { cell.backgroundColor = theme.tableViewCellBackgroundColor cell.textLabel?.textColor = theme.tableViewCellTextColor } func theme(_ view: UIView) { view.backgroundColor = theme.tableViewBackgroundColor } }
58. Theming
59. Debug Menus
60. x4
61. Story Time
62. Dequeueing TableView Cells
63. let cell = tableView.dequeueReusableCellWithIdentifier("CustomCell", forIndexPath: indexPath) as! CustomCell
64. let cell = tableView.dequeue(cellOfType: CustomCell.self, indexPath: indexPath)
65. let cell = tableView.dequeueReusableCellWithIdentifier("CustomCell", forIndexPath: indexPath) as! CustomCell let cell = tableView.dequeue(cellOfType: CustomCell.self, indexPath: indexPath)
66. Problem
67. Pain Threshold
68. Safe. Expressive. Testable.
70. RanchWeather https://github.com/bignerdranch/RanchWeather Thank you.