Swift - Beyond Beginner

Transcript

1. DEVNEXUS Atlanta – February 22, 2018 Swift Patrick Seda - @pxtrick
2. Target Tools
3. Beginner Target Tools @pxtrick
4. Target Tools @pxtrick “Beyond Beginner” This
5. Background
6. Background @pxtrick “The Effects of RR-Interval Data on Heart Rate Variability and Congestive Heart Failure” Then: Now: Mobile and Web Business Apps Atlanta-ish, GA @pxtrick Patrick Seda Increasing the Quality of the Universe
7. Access Control
8. public open internal fileprivate private Access Control @pxtrick
9. file 2 class A class B file 1 module “consumer” Access Control @pxtrick class C
10. file 2 class A class B file 1 module “consumer” // Class with a member variable. class A { private var value } Access Control @pxtrick class C
11. file 2 class A class B file 1 module “consumer” // Class with a member variable. class A { fileprivate var value } Access Control @pxtrick class C
12. class C file 2 class A class B file 1 module “consumer” // Class with a member variable. class A { internal var value } Access Control @pxtrick
13. file 2 class A class B file 1 module “consumer” // Class with a member variable. class A { public var value // Accessible, no override } Access Control @pxtrick class C
14. file 2 class A class B file 1 module “consumer” // Class with a member variable. class A { open var value // Accessible, can override } Access Control @pxtrick class C
15. Most restrictive Least restrictive Access Control @pxtrick
16. -open -public -internal -fileprivate -private Access Control @pxtrick Most restrictive Least restrictive Default!
17. Why is the default level internal? “When you write a simple single-target app, the code in your app is typically self-contained within the app and doesn’t need to be made available outside of the app’s module. The default access level of internal already matches this requirement. Therefore, you don’t need to specify a custom access level.” Because: Less typing for small apps! Access Control @pxtrick
18. -open -public -internal -fileprivate -private What should we do? Access Control @pxtrick Most restrictive Least restrictive
19. Named Model Types
20. enum vs. struct vs. class Named Model Types @pxtrick
21. enum Named Model Types @pxtrick
22. // Modeling a Finite-State Machine. // State of the system. enum AlarmState { case disarmed case armed case alarming } // System-wide events. enum Event { case arm case disarm case tripSensor } Named Model Types @pxtrick
23. var currentState: AlarmState func handleEvent(_ event: Event) { switch event { case .arm: if (currentState == .disarmed) { currentState = .armed } case .disarm: currentState = .disarmed case .tripSensor: if (currentState == .armed) { currentState = .alarming } } } Named Model Types @pxtrick
24. var currentState: AlarmState = .disarmed handleEvent(.arm) // currentState == .armed handleEvent(.tripSensor) // currentState == .alarming handleEvent(.disarm) // currentState == .disarmed handleEvent(.tripSensor) // currentState == .disarmed Named Model Types @pxtrick
25. // Define some Gibson guitar types enum Gibson: String { case lesPaul case es355 case flyingV case sg } Named Model Types @pxtrick
26. // Define some Gibson guitar types enum Gibson: String { case lesPaul case es355 case flyingV case sg } let myGuitar = Gibson.lesPaul print("My guitar is a \(myGuitar.rawValue)") let yourGuitar: Gibson = .flyingV print("Your guitar is a \(yourGuitar.rawValue)") My guitar is a lesPaul Your guitar is a flyingV Named Model Types @pxtrick Ou t p u t :
27. // Define some Gibson guitar types enum Gibson: String { case lesPaul = "Les Paul" case es355 = "ES355" case flyingV = "Flying V" case sg = "SG" } let myGuitar = Gibson.lesPaul print("My guitar is a \(myGuitar.rawValue)") let yourGuitar: Gibson = .flyingV print("Your guitar is a \(yourGuitar.rawValue)") My guitar is a Les Paul Your guitar is a Flying V Named Model Types @pxtrick Ou t p u t :
28. struct & class Named Model Types @pxtrick
29. When should we use struct vs. class? “In all other cases, define a class, and create instances of that class to be managed and passed by reference. In practice, this means that most custom data constructs should be classes, not structures.” Use a struct when: - Encapsulate few, simple data values - Data can be copied (passed by value) - Does not need inheritance Named Model Types @pxtrick
30. Protocols for Design
31. Let’s Design A game! Protocols for Design @pxtrick
32. Protocols for Design @pxtrick
33. Design before coding! Protocols for Design @pxtrick
34. Musician Musical Instrument Stringed Instrument Cello Viola Violin Bass makeSound() numStrings perform() Protocols for Design @pxtrick
35. protocol MusicalInstrument { func makeSound() } protocol StringedInstrument: MusicalInstrument { var numStrings: Int { get } } extension StringedInstrument { func makeSound() { print("Plink") } } class Cello: StringedInstrument { var numStrings: Int = 4 func makeSound() { print(”Hurrm Hummm") } } class Bass: StringedInstrument { var numStrings: Int = 4 func makeSound() { print("A Boom Boom Boom") } } Protocols for Design @pxtrick
36. class Musician { var instrument: MusicalInstrument? func perform() { instrument?.makeSound() } } let cello: MusicalInstrument = Cello() let bass: MusicalInstrument = Bass() let musician = Musician() musician.instrument = cello musician.perform() musician.instrument = bass musician.perform() Hurrm Hummm A Boom Boom Boom Protocols for Design @pxtrick Ou t p u t :
37. CLosures
38. callbacks Closures @pxtrick
39. // Do some stuff and then fire a callback. func doSomething( /* ??? */ ) { // ... onDone() } Closures - C a l lb a cks @pxtrick
40. // Increment an integer and fire a callback. func increment(_ value: inout Int, onDone onDone: () -> Void) { value += 1 onDone() } // Define our callback. var attentionCb = { print("Attention! value = \(value)") } // Test it out. var value = 3; increment(&value, onDone: attentionCb) increment(&value, onDone: attentionCb) Attention! value = 4 Attention! value = 5 @pxtrick Ou t p u t : Closures - C a l lb a cks
41. time of execution Closures @pxtrick
42. var queue = DispatchQueue.global() // Run using a thread pool. func execute(_ work: () -> Void) { queue.sync { work() } } // Create some work. var workItemOne = { print("Work item 1") } var workItemTwo = { print("Work item 2") } execute(workItemOne) execute(workItemTwo) Work item 1 Work item 2 @pxtrick Ou t p u t : Closures - T i m e of E xecu t ion
43. var queue = DispatchQueue.global() // Run using a thread pool. func execute(_ work: () -> Void) { queue.async { work() } } // Create some work. var workItemOne = { print("Work item 1") } var workItemTwo = { print("Work item 2") } execute(workItemOne) execute(workItemTwo) error: closure use of non-escaping parameter 'work' may allow it to escape @pxtrick Ou t p u t : Closures - T i m e of E xecu t ion
44. var queue = DispatchQueue.global() // Run using a thread pool. func execute(_ work: @escaping () -> Void) { queue.async { work() } } // Create some work. var workItemOne = { print("Work item 1") } var workItemTwo = { print("Work item 2") } execute(workItemOne) execute(workItemTwo) Work item 2 Work item 1 @pxtrick Ou t p u t : Closures - T i m e of E xecu t ion
45. Closure Expressions Closures @pxtrick
46. let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Define a normal comparison function. func backwards(_ s1: String, _ s2: String) { return s1 > s2 } // Execute the array sort. var reversedOrder = cities.sorted(by: backwards) print("\(reversedOrder)") ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : Closures - C l os u r e E xp r e s s io n s
47. let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Closure Expression syntax. var reversedOrder = cities.sorted(by: { (s1: String, s2: String) -> Bool in return s1 > s2 }) ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : Closures - C l os u r e E xp r e s s io n s
48. let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Inferring type from context. var reversedOrder = cities.sorted(by: { s1, s2 in return s1 > s2 }) ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : Closures - C l os u r e E xp r e s s io n s
49. let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Implicit returns from single-expression closures. var reversedOrder = cities.sorted(by: { s1, s2 in s1 > s2 }) ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : Closures - C l os u r e E xp r e s s io n s
50. let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Shorthand argument names. var reversedOrder = cities.sorted(by: { $0 > $1 }) ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : Closures - C l os u r e E xp r e s s io n s
51. let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Operator methods. var reversedOrder = cities.sorted(by: >) ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : Closures - C l os u r e E xp r e s s io n s
52. let cities = ["Geneva", "Traer", "Mint Hill", "Senoia"] // Operator methods. var reversedOrder = cities.sorted(by: >) ["Traer", "Senoia", "Mint Hill", "Geneva"] @pxtrick Ou t p u t : // Closure Expression syntax. var reversedOrder = cities.sorted(by: { (s1: String, s2: String) -> Bool in return s1 > s2 }) Previously: Closures - C l os u r e E xp r e s s io n s
53. Memory Leaks
54. ARC – Automatic Reference Counting Memory Leaks @pxtrick
55. // A rockin’ band. class RockBand { var keys: Keyboard? deinit { print("[RockBand] - deinit()") } } // A tasty delight. class Keyboard { var band: RockBand? deinit { print("[Keyboard] - deinit()") } } Memory Leaks @pxtrick
56. // Create our band. var band: RockBand? = RockBand() // Create our keys. var keys: Keyboard? = Keyboard() // Establish a beautiful friendship. band?.keys = keys keys?.band = band // Clean up. print("Removing band ...") band = nil print("Removing keys ...") keys = nil Removing band ... Removing keys ... Memory Leaks @pxtrick Ou t p u t :
57. var band strong strong strong var keys strong <RockBand instance> keys: <Keyboard instance> band <Keyboard instance> band: <RockBand instance> keys Memory Leaks @pxtrick
58. var band strong strong var keys strong <RockBand instance> keys: <Keyboard instance> band <Keyboard instance> band: <RockBand instance> keys Memory Leaks @pxtrick
59. var band strong strong var keys <RockBand instance> keys: <Keyboard instance> band <Keyboard instance> band: <RockBand instance> keys Memory Leaks @pxtrick
60. // A rockin’ band. class RockBand { var keys: Keyboard? deinit { print("[RockBand] - deinit()") } } // A tasty delight. class Keyboard { weak var band: RockBand? deinit { print("[Keyboard] - deinit()") } } Memory Leaks @pxtrick
61. var band strong strong var keys strong <RockBand instance> keys: <Keyboard instance> band <Keyboard instance> band: <RockBand instance> keys Memory Leaks @pxtrick weak
62. var band strong var keys strong <RockBand instance> keys: <Keyboard instance> band <Keyboard instance> band: <RockBand instance> keys Memory Leaks @pxtrick weak
63. var band var keys strong <RockBand instance> keys: <Keyboard instance> band <Keyboard instance> band: <RockBand instance> keys Memory Leaks @pxtrick
64. var band var keys <RockBand instance> keys: <Keyboard instance> band <Keyboard instance> band: <RockBand instance> keys Memory Leaks @pxtrick
65. var band var keys <RockBand instance> keys: <Keyboard instance> band <Keyboard instance> band: <RockBand instance> keys Memory Leaks @pxtrick
66. // Create our band. var band: RockBand? = RockBand() // Create our keys. var keys: Keyboard? = Keyboard() // Establish a beautiful friendship. band?.keys = keys keys?.band = band // Clean up. print("Removing band ...") band = nil print("Removing keys ...") keys = nil Removing band ... [RockBand] - deinit() Removing keys ... [Keyboard] - deinit() Memory Leaks @pxtrick Ou t p u t :
67. // A rock show. class Concert { var fans: Audience? deinit { print("[Concert] - deinit()") } } // The fans. class Audience { var concert: Concert init(_ concert: Concert) { self.concert = concert } deinit { print("[Audience] - deinit()") } } Memory Leaks @pxtrick
68. // Create our rock show. var rockShow: Concert? = Concert() // Create and assign our fans. rockShow?.fans = Audience(rockShow!) // Clean up. print("Removing rockShow...") rockShow = nil Removing rockShow ... Memory Leaks @pxtrick Ou t p u t :
69. var rockShow <Concert instance> fans: <Audience instance> rockShow <Audience instance> concert: <Concert instance> audience strong strong strong Memory Leaks @pxtrick
70. var rockShow strong strong <Concert instance> fans: <Audience instance> rockShow <Audience instance> concert: <Concert instance> audience Memory Leaks @pxtrick
71. // A rock show. class Concert { var fans: Audience? deinit { print("[Concert] - deinit()") } } // The fans. class Audience { unowned var concert: Concert init(_ concert: Concert) { self.concert = concert } deinit { print("[Audience] - deinit()") } } Memory Leaks @pxtrick
72. var rockShow <Concert instance> fans: <Audience instance> rockShow <Audience instance> concert: <Concert instance> audience strong strong Memory Leaks @pxtrick unowned
73. var rockShow <Concert instance> fans: <Audience instance> rockShow <Audience instance> concert: <Concert instance> audience strong Memory Leaks @pxtrick unowned
74. var rockShow <Concert instance> fans: <Audience instance> rockShow <Audience instance> concert: <Concert instance> audience Memory Leaks @pxtrick
75. // Create our rock show. var rockShow: Concert? = Concert() // Create and assign our fans. rockShow?.fans = Audience(rockShow!) // Clean up. print("Removing rockShow...") rockShow = nil Removing rockShow ... [Concert] - deinit() [Audience] - deinit() Ou t p u t : Memory Leaks @pxtrick
76. DEVNEXUS Atlanta – February 22, 2018 Thank You Patrick Seda - @pxtrick