Elements of Functional Programming

Delivered at dotSwift 2018: Functional programming might seem scary at first, but with some hands-on examples you'll soon find you can use map(), flatMap(), filter(), and more in your own projects and see some real benefits.

Presented at dotSwift 2018, Paris.

Transcript

1. PAUL HUDSON — @twostraws ELEMENTS OF FUNCTIONAL PROGRAMMING www.hackingwithswift.com
2. WHAT’S THE GOAL?
3. MONADS FUNCTORS APPLICATIVES
6. WHY BOTHER?
14. CODE IS
 COMING
15. MAP
17. [1, 2, 3, 4]
18. [2, 4, 6, 8]
19. camping parking weekend
20. le camping le parking le weekend
21. John Paul
 George Ringo 4 4 6 5
22. var result = [Int]() for string in strings { result.append(string.count) } return result func lengthOf(strings: [String]) -> [Int] { }
23. return strings.map { $0.count } func lengthOf(strings: [String]) -> [Int] { }
24. return strings.map { $0.count } func lengthOf(strings: [String]) -> [Int] { }
25. return strings.map { $0.count } func lengthOf(strings: [String]) -> [Int] { }
28. func map<T>(_ transform: (Element) -> T) -> [T] { var returnValue = [T]() for item in self { returnValue.append(transform(item)) } return returnValue }
30. let scores = [100, 80, 85] let formatted = scores.map { “Your score was \($0)” }
31. let strings = [“am”, “stram”, “gram”] let result = strings.map { $0.uppercased() }
32. let numbers = [4.0, 9.0, 16.0] let result = numbers.map(sqrt)
33. animate(withDuration: 5)
34. FLATMAP COMPACTMAP
37. init?() try? as?
38. let a = Int(“5”)
39. a: Int? = 5
40. let b = Int(“non”)
41. b: Int? = nil
42. let input = [“1”, “5”, “Fish”] let numbers = input.flatMap { Int($0) } [Int]
43. [“1”, “5”, “Fish”] [Optional(1), Optional(5), nil] [1, 5]
44. let validURLs = strings.flatMap { URL(string: $0) }
45. let imageViews = views.flatMap { $0 as? UIImageView }
46. let valid = users.flatMap { $0 }
47. OPTIONALS
48. let greet = name.map { “Hi, \($0)!” } print(greet ?? “Unknown user”) let name: String? = getUser(id: 97)
49. let greet: String if let name = name { greet = "Hi, \(name)!" } else { greet = "Unknown user" } print(greet) let name: String? = getUser(id: 97)
50. let number: String? = “5” let result = number.map { Int($0) } Int
51. let number: String? = “5” let result = number.map { Int($0) } Int?
52. let number: String? = “5” let result = number.map { Int($0) } Int??
53. WTF?
54. let number: String? = “5” let result = number.map { Int($0) }
55. let number: String? = “5” let result = number.flatMap { Int($0) } Int?
56. map() Optional<Optional<Int>> flatMap() Optional<Int>
57. FILTER
59. FILTER
60. let goodWine = wine.filter { $0.origin == “France” }
61. let banned = players.filter { $0.hasPrefix(“Kevin”) }
62. let numbers = [1, 2, 3, 4, 5] let odd = numbers.filter { $0 % 2 == 1 }
63. MORE
64. let firstHigh = scores.first { $0 > 85 }
65. let ints = [9, 5, 3, 5] let counts = ints.map { ($0, 1) } // [(9, 1), (5, 1), (3, 1), (5, 1)] let dict = Dictionary(counts, uniquingKeysWith: +) // [9: 1, 5: 2, 3: 1]
66. let numbers = Array(1…100) let sum = numbers.reduce(0, +)
67. let yes = [“oui”, “ouais”, “bien sûr”] yes.contains(“oui”)
68. let reply = “ma réponse est oui” reply.contains(“oui”)
69. let yes = [“oui”, “ouais”, “bien sûr”] let reply = “ma réponse est oui” yes.contains(where: reply.contains)
70. CHALLENGES
74. WRAP UP
78. PAUL HUDSON — @twostraws Merci beaucoup! www.hackingwithswift.com