Balance

Balancing the new awesome with Swift, and the old ways with Objective C is not always easy. I went over some of the things I've learned over the years putting the two worlds together.

Transcript

1. Balance Saul Mora @casademora saul@casademora.com
2. Journey…
4. Functions Protocols Objects
5. Unlearn what you have learned…
6. nil
7. Optionals?
11. >>- <^> <*>
12. flatMap map apply
13. let fileManager = NSFileManager() if let filePath = fileURL.path { if fileManager.fileExistsAtPath(filePath) { var error: NSError? let fileAttributes = fileManager.attributesOfItemAtPath(filePath, error: &error) if let fileAttributes = fileAttributes { if let creationDate = fileAttributes[NSFileModificationDate] as? NSDate { return creationDate .isBefore(NSDate.oneDayAgo()) } } else { NSLog("No file attributes \(filePath)") } } }
14. return filePath >>- fileExists >>- retrieveFileAttributes >>- extractCreationDate >>- checkExpired ?? false
15. Functional operator all the things
16. extension Bundle { var bundleVersion: String { let bundleVersionKey = kCFBundleVersionKey as String let bundleShortVersionkey = "CFBundleShortVersionString" let version = (infoDictionary >>- { $0[bundleVersionKey] }) ?? (infoDictionary >>- { $0[bundleShortVersionkey] }) return version as? String ?? "0.0.0" } }
17. extension Bundle { var bundleVersion: String { let bundleVersionKey = kCFBundleVersionKey as String let bundleShortVersionkey = "CFBundleShortVersionString" let version = (infoDictionary >>- { $0[bundleVersionKey] }) ?? (infoDictionary >>- { $0[bundleShortVersionkey] }) return version as? String ?? "0.0.0" } } import Runes
18. Frameworks?
19. extension Bundle { var bundleVersion: String { let bundleVersionKey = kCFBundleVersionKey as String let bundleShortVersionkey = "CFBundleShortVersionString" let version = (infoDictionary >>- { $0[bundleVersionKey] }) ?? (infoDictionary >>- { $0[bundleShortVersionkey] }) return version as? String ?? "0.0.0" } } import Runes
20. extension Bundle { private var bundleInfo: [String: Any] { return infoDictionary ?? [:] } var bundleVersion: String { let bundleVersionKey = kCFBundleVersionKey as String let bundleShortVersionkey = "CFBundleShortVersionString" let version = (infoDictionary >>- { $0[bundleVersionKey] }) ?? (infoDictionary >>- { $0[bundleShortVersionkey] }) return version as? String ?? "0.0.0" } } import Runes
21. extension Bundle { private var bundleInfo: [String: Any] { return infoDictionary ?? [:] } var bundleVersion: String { let bundleVersionKey = kCFBundleVersionKey as String let bundleShortVersionkey = "CFBundleShortVersionString" let version = bundleInfo[bundleVersionKey] ?? bundleInfo[bundleShortVersionkey] return version as? String ?? "0.0.0" } }
22. !
23. ! • Remove a framework • Code is using standard operators • Less complex syntax
24. Why does it fail
25. "
26. Optional<T>
27. Result<T, Error>
28. let result: Result<T, Error> = … result.map { // use value ($0) in here } .mapError { error and in // handle error here }
29. throws
30. func doSomething() throws -> Double { throw MyErrors.hadNothingToDo }
31. func doSomethingAsync() throws -> Double { DispatchQueue.background.async { throw MyErrors.hadNothingToDo } }
32. func doSomethingAsync() throws -> Double { do { DispatchQueue.background.async { throw MyErrors.hadNothingToDo } } catch { ///... } }
33. Promise
34. let promise = doSomething() promise.then { // use promised value ($0) in here } .catch { error and in // handle error here }
35. func doSomething() -> Promise<Double> { return Promise { fulfill, reject in /// if success { fulfill(10.0) } else { reject(MyError.unableToCompute) } }
36. !
37. message based
38. Object''' Object'' Object' Object
39. Object''' Object'' Object' Object
40. Object''' Object'' Object' Object Another Object doSomething
41. forwardingTarget(for: Selector)
42. Module Module Module App
43. Module Module Module App
44. App
45. App Coordinator Coordinator Coordinator
46. Host App Coordinator Coordinator Coordinator
47. Host App Coordinator Coordinator Coordinator
48. class Coordinator: NSObject { var next: Coordinator? override func forwardingTarget(for aSelector: Selector!) -> Any? { return next } }
49. class ModuleHost { let loginModule = LoginModule() let main = MainModule() let profile = ProfileModule() var messageBus: AnyObject { return main.coordinator } func setup() { main.coordinator.next = loginModule.coordinator loginModule.coordinator.next = profile.coordinator } }
50. //... host.messageBus.login() host.messageBus.loginComplete() let mainView = host.messageBus.mainUI() host.messageBus.showMainUI() host.messageBus.displayProfile() //...
51. http://tinyurl.com/DynamicCoordinatorDemo
52. Singletons
53. +(MyClass *)singleton { static MyClass *shared = nil; if(shared == nil) { shared = [[MyClass alloc] init]; } return shared; }
54. +(MyClass *)singleton { static dispatch_once_t token; static MyClass *shared = nil; dispatch_once(&token, ^{ shared = [[MyClass alloc] init]; }); return shared; }
55. struct MyClass {
 static let shared: MyClass = MyClass()
 }
56. KEEP CALM SINGLETONS ARE NOT SPECIAL AND REALIZE
57. Treat singleton objects like other objects
58. Protocols
59. class MyResource { // slow, expensive object static let `default`: MyResource }
60. protocol ResourceUsable { var currentResource: MyResource { get } } extension ResourceUsable { var currentResource: MyResource { return MyResource.default } } class MyResource { // slow, expensive object static let `default`: MyResource }
61. class MyClient: ResourceUsable { func usesResource() { currentResource.performOperation() } }
64. class MyClient: ResourceUsable { var currentResource: MyResource = .default func useResource() { currentResource.performOperation() } }
65. class ClientTest: XCTestCase { fun testSomething() { let client = Client() client.currentResource = fakeResource XCTAssertNotNil(client.performUpdateFromResource()) } }
66. KVO
67. open func addObserver(_ observer: NSObject, forKeyPath keyPath: String, options: NSKeyValueObservingOptions = [], context: UnsafeMutableRawPointer?)
68. class SomeView: UIView { var observedProgress: Progress? { didSet { observedProgress?.addObserver(self, forKeyPath: #keyPath(Progress.fractionCompleted), options: [.initial, .new], context: nil) } } }
69. class SomeView: UIView { var observedProgress: Progress? { willSet { observedProgress?.removeObserver(self, forKeyPath: #keyPath(Progress.fractionCompleted), context: nil) } didSet { observedProgress?.addObserver(self, forKeyPath: #keyPath(Progress.fractionCompleted), options: [.initial, .new], context: nil) } } }
70. private var observingContext = 0 class SomeView: UIView { var observedProgress: Progress? { willSet { observedProgress?.removeObserver(self, forKeyPath: #keyPath(Progress.fractionCompleted), context: &observingContext) } didSet { observedProgress?.addObserver(self, forKeyPath: #keyPath(Progress.fractionCompleted), options: [.initial, .new], context: &observingContext) } } }
71. class SomeView: UIView { //… override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {} }
72. override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) { guard &observingContext == context else { super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context) return } }
73. override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) { guard &observingContext == context else { super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context) return } let value = change?[.newKey] as? Double }
74. override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) { guard &observingContext == context else { super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context) return } if let value = change?[.newKey] as? Double { renderProgress(value) //UI drawing } }
75. override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) { guard &observingContext == context else { super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context) return } if object == observedProgress && keyPath == #keyPath(Progress.fractionCompleted) { if let value = change?[.newKey] as? Double { renderProgress(value) } } }
76. override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) { guard &observingContext == context else { super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context) return } guard object == observedProgress, keyPath == #keyPath(Progress.fractionCompleted), let value = change?[.newKey] as? Double else { return } renderProgress(value) }
77. What value does the client object really want to observe?
78. class EasierObserving: UIView { var progress: Progress? { willSet { progress?.observeFractionCompleted = nil } didSet { progress?.observeFractionCompleted = renderProgress } } func renderProgress(_ value: Double) { //... } }
79. protocol ProgressObservable { typealias ProgressReportingFunction = (Double) -> Void var observeFractionCompleted: ProgressReportingFunction? { get set } }
80. class EasierObserving: UIView { var progress: ProgressObservable? { willSet { progress?.observeFractionCompleted = nil } didSet { progress?.observeFractionCompleted = renderProgress } } func renderProgress(_ value: Double) { //... } }
81. class Progress: ProgressObservable { var observeFractionCompleted: (Double) -> Void }
82. Composition Inheritance or
83. class EazyProgress: ProgressObservable { let progress: Progress init(progress: Progress) { self.progress = progress } var observeFractionCompleted: ProgressObservable.ProgressReportingFunction? }
84. init(progress: Progress) { self.progress = progress super.init() progress.addObserver(self, forKeyPath: #keyPath(Progress.fractionCompleted), options: [.initial, .new], context: &observingContext) } deinit { progress.removeObserver(self, forKeyPath: #keyPath(progress.fractionCompleted), context: &observingContext) }
85. extension Progress: ProgressObservable { func observeFractionCompleted(_ handler: @escaping (Double) -> Void) -> ProgressObservable //must keep this object to maintain connection { let observer = ProgressFractionCompletedObserver(progress: self) observer.observeFractionCompleted = handler return observer } }
86. class Client: UIView { var observerToken: ProgressObservable! func setup() { let view = UIProgressView() let progress = Progress() observerToken = progress.observeFractionCompleted { view.progress = Float($0) } } }
87. So…
88. What does all this mean?
90. Protocols Objects Functions
91. Functions are really great at calculating state Objects are really great at presenting state Protocols are really great at communicating state
92. Balance
93. Questions?
94. kthxbai