Alexander Voronov

Swift: Going Functional
https://youtu.be/Dc9aKhs37BE

1. Swift Rocks 2! Alexander Voronov iOS Developer @ Stanfy
2. Swift Going Functional
3. What is Functional Programming?
4. Functional Programming
5. Functional Programming • Higher-order functions
6. Functional Programming • Higher-order functions • Immutable states & pure functions
7. Functional Programming • Higher-order functions • Immutable states & pure functions • Modularity
8. Functional Programming • Higher-order functions • Immutable states & pure functions • Modularity • Types
9. Swift Power
10. Swift Power
11. Swift Power • First Class Functions
12. Swift Power • First Class Functions • Currying
13. Swift Power • First Class Functions • Currying • Generics
14. Swift Power • First Class Functions • Currying • Generics • Type Inference
15. Swift Power • First Class Functions • Currying • Generics • Type Inference • Enums
16. First Class Functions func add(x: Int) -> Int -> Int { return { y in y + x } } let addOne = add(1) addOne(2) // 3
17. First Class Functions func addTwo(x: Int) -> Int { return x + 2 } (1...5).map(addTwo) // [3, 4, 5, 6, 7]
18. Currying func add(a: Int)(b: Int) -> Int { return a + b } let addOne = add(1) let xs = 1...5 xs.map(addOne) // [2, 3, 4, 5, 6]
19. Currying func curry<A, B, C>(f: (A, B) -> C) -> A -> B -> C { return { a in { b in f(a, b) } } }
20. Generics func printEach<T: SequenceType>(items: T) { for item in items { print(item) } } printEach(1...5) printEach(["one", "two", "three"])
21. Type Inference let x = 42.0 x.dynamicType // Double x is Double // true
22. Type Inference var xs = [1, 5, 2, 4, 3] xs.sort(<) print(xs) // [1, 2, 3, 4, 5]
23. Type Inference var xs = [1, 5, 2, 4, 3] xs.sort(<) print(xs) // [1, 2, 3, 4, 5]
24. Type Inference let xs = [1, 5, 2, 4, 3] let ys = xs.sorted(<) print(xs) // [1, 5, 2, 4, 3] print(ys) // [1, 2, 3, 4, 5]
25. Type Inference let xs = [1, 5, 2, 4, 3] let ys = xs.sorted(<) print(xs) // [1, 5, 2, 4, 3] print(ys) // [1, 2, 3, 4, 5]
26. Enumerations enum Fruit: String { case Apple = "apple" case Banana = "banana" case Cherry = "cherry" } Fruit.Apple.rawValue // "apple"
27. Enumerations enum ValidationResult { case Valid case NotValid(NSError) }
28. Enumerations enum MyApi { case xAuth(String, String) case GetUser(Int) } extension MyApi: MoyaTarget { var baseURL: NSURL { return NSURL(string: "")! } var path: String { switch self { case .xAuth: return "/authorise" case .GetUser(let id): return "/user/\(id)" } } } https://github.com/Moya/Moya
29. Optionals enum Optional<T> { case None case Some(T) } var x = 5 x = nil // Error!
30. Optional Chaining struct Dog { var name: String } struct Person { var dog: Dog? } let dog = Dog(name: "Dodge") let person = Person(dog: dog) let dogName = person.dog?.name
31. Optional Chaining struct Dog { var name: String } struct Person { var dog: Dog? } let dog = Dog(name: "Dodge") let person = Person(dog: dog) let dogName = person.dog?.name Optional Chaining
32. Functors, Applicatives, Monads
34. Functors, Applicatives, Monads let x = 2 x + 3 // == 5
35. Functors, Applicatives, Monads let x = 2 x + 3 // == 5 let y = Optional(2)
36. Functors let y = Optional(2) y + 3 // Error! // Value of optional type // Optional<Int> not unwrapped
37. Functors let y = Optional(2) y.map { $0 + 3 } // Optional(5)
38. Functors func map<U>(f: T -> U) -> U? { switch self { case .Some(let x): return f(x) case .None: return .None } }
39. Functors infix operator <^> { associativity left } func <^><T, U>(f: T -> U, a: T?) -> U? { return a.map(f) }
40. Functors func <^><T, U>(f: T -> U, a: T?) -> U? { return a.map(f) } let addOne = { $0 + 1 } addOne <^> Optional(2) // Optional(3)
41. Applicative func apply<U>(f: (T -> U)?) -> U? { switch f { case .Some(let someF): return self.map(someF) case .None: return .None } }
42. Applicatives infix operator <*> { associativity left } func <*><T, U>(f: (T -> U)?, a: T?) -> U? { return a.apply(f) }
43. Applicatives infix operator <*> { associativity left } func <*><T, U>(f: (T -> U)?, a: T?) -> U? { return a.apply(f) } func add(a: Int)(b: Int) -> Int { return a + b }
44. Applicatives add <^> Optional(2) <*> Optional(3) // Optional(5)
45. Applicatives add <^> Optional(2) <*> Optional(3) // Optional(5)
46. Applicatives add <^> Optional(2) <*> Optional(3) // Optional(5) let a = add <^> Optional(2)
47. Applicatives add <^> Optional(2) <*> Optional(3) // Optional(5) let a = add <^> Optional(2)
48. Applicatives add <^> Optional(2) <*> Optional(3) // Optional(5) let a = add <^> Optional(2) let a: (b: Int) -> Int?
49. Monads typealias T = Double let f: T -> T = { $0 * 2.0 } let g: (T, T) -> T = { $0 / $1 }
50. Monads typealias T = Double let f: T -> T = { $0 * 2.0 } let g: (T, T) -> T = { $0 / $1 } f(g(4, 2))
51. Monads typealias T = Double let f: T -> T = { $0 * 2.0 } let g: (T, T) -> T = { $0 / $1 } f(g(4, 2)) g: (T, T) -> T?
52. Monads typealias T = Double let f: T -> T = { $0 * 2.0 } let g: (T, T) -> T = { $0 / $1 } f(g(4, 2)) g: (T, T) -> T? g(4, 2) >>- { f($0) }
53. Monads >>- == http://adit.io/posts/2013-04-17-functors,_applicatives,_and_monads_in_pictures.html
54. Monads func flatten<U>(a: U??) -> U? { switch a { case .Some(let someA): return someA case .None: return .None } }
55. Monads func flatMap<U>(f: T -> U?) -> U? { return flatten(map(f)) }
56. Monads func flatMap<U>(f: T -> U?) -> U? { return flatten(map(f)) } func map<U>(f: T -> U) -> U?
57. Monads func flatMap<U>(f: T -> U?) -> U? { return flatten(map(f)) } func map<U>(f: T -> U) -> U?
58. Monads func flatMap<U>(f: T -> U?) -> U? { return flatten(map(f)) } func map<U>(f: T -> U) -> U? func map<U?>(f: T -> U?) -> U??
59. Monads infix operator >>- { associativity left } func >>-<T, U>(a: T?, f: T -> U?) -> U? { return a.flatMap(f) }
60. Monads func half(a: Int) -> Int? { return a % 2 == 0 ? a / 2 : .None }
61. Monads func half(a: Int) -> Int? { return a % 2 == 0 ? a / 2 : .None } Optional(8) >>- half >>- half // Optional(2)
62. Monad Laws • Left Identity • Right Identity • Associativity
63. Left Identity Law let f = { Optional($0 + 1) } let a = 1 let x = Optional(a) >>- f let y = f(a) x == y
64. Right Identity Law func create<T>(value: T) -> T? { return Optional(value) } let x = Optional(1) >>- create let y = Optional(1) x == y
65. Associativity Law let double = { Optional(2 * $0) } let triple = { Optional(3 * $0) } let x = Optional(1) >>- double >>- triple let y = Optional(1) >>- { double($0) >>- triple } let z = { Optional(1) >>- double }() >>- triple x == y y == z
66. Recap Functor map<U>(f: T -> U) -> M<U> Applicative apply<U>(f: M<(T -> U)>) -> M<U> Monad flatMap<U>(f: T -> M<U>) -> M<U>
67. Pipes & Railways @ScottWlaschin
68. Pipes infix operator |> { associativity left } public func |> <T, U>(x: T, f: T -> U) -> U { return f(x) } let addTwo = { $0 + 2 } let prodThree = { $0 * 3 } 5 |> addTwo |> prodThree |> print // 21
69. Pipes let transformedX = x |> addTwo |> prodThree |> increment |> square |> pow VS (pow(square(increment(prodThree(addTwo(x))))))
70. Railways http://fsharpforfunandprofit.com/posts/recipe-part2/
71. Argo JSON Parser + Argo Runes
72. Argo Example extension Model: Decodable { static func decode(json: JSON) -> Decoded<Model> { return Model.create <^> json <| "id" <*> json <| "room" <*> json <| "guest_name" <*> json <| "status" <*> json <| "label" <*> json <|? "user_comment" <*> json <| ["channel", "label"] <*> json <| "severity" <*> json <|| "epochs" <*> json <|| "body" } }
73. Argo Example let entities: [Model]? entities = data?.json() >>- { $0["entities"] } >>- decode
74. Where Next?
75. Where Next • Functors, Applicatives and Monads in Pictures • Railway Oriented Programming • Functional Programming in Swift (Objc.io) • Argo • Swiftz • RxSwift • ReactiveCocoa-3.0 • Haskell, F#, Erlang, Elm
76. Thanks!
77. Comments / Questions? @aleks_voronov a-voronov