Poor man's functional programming

Getting started with new paradigms requires us to change thinking and make mistakes along the way. Functional programming from the eyes of the beginner, along with practical steps to gradually change how we write our code.

Transcript

1. POOR MAN’S FUNCTIONAL PROGRAMMING
2. HI! @miguelquinon http://miqu.me
3. WHY FP?
4. !
5. !
6. !
7. !
8. ! (PRODUCT_NAME)
9. CONTROLLING COMPLEXITY
10. WHY NOW? SWIFT == CHANGE CHANGE == OPPORTUNITY
11. 1. BEGINNER’S POINT OF VIEW 2. PRACTICAL FP 3. BEYOND BASICS
12. BEGINNER’S POINT OF VIEW
13. HIGHER ORDER FUNCTIONS NO SIDE EFFECTS
18. LEARNING FP FEELS HARD
20. TOOLS NOT RELIGIONS UI AND IOS SWIFT IS NOT PURE FP LANGUAGE SIDE EFFECTS ARE NECESSARY
21. PRACTICAL FP
22. 1. KNOW YOUR FUNCTIONS 2. PROFIT!
23. KNOW YOUR FUNCTIONS 1. SIGNATURES 2. SWIFT SYNTAX 3. FUNCTIONS EVERYWHERE!
24. FUNCTIONS EVERYWHERE! func animation() { self.view.transform = CGAffineTransformMakeScale(0.5, 0.5) } UIView.animateWithDuration(0.4, animations: animation)
25. FUNCTIONS EVERYWHERE! let animation = { view.transform = CGAffineTransformMakeScale(0.5, 0.5) } UIView.animateWithDuration(0.4, animations: animation)
26. FUNCTIONS EVERYWHERE! struct Person { let name: String let surname: String } extension Person { var displayName { return "\(name) \(surname)" } }
27. FUNCTIONS EVERYWHERE! extension Person { func greeting() -> String { return "Hello my name is \(name)" } } let me = Person(name: "Miguel", surname: "Quinones") let john = Person(name: "John", surname: "Doe") let greeter = Person.greeting let a = greeter(me)() // Hello my name is Miguel let b = greeter(john)() // Hello my name is John
28. BASIC FUNCTIONS MAP FILTER REDUCE FLATMAP
29. KNOW THE BASIC FUNCTIONS extension CollectionType { func map<T>(@noescape transform: (Self.Generator.Element) throws -> T) rethrows -> [T] func filter(@noescape includeElement: (Self.Generator.Element) throws -> Bool) rethrows -> [Self.Generator.Element] func reduce<T>(initial: T, @noescape combine: (T, Self.Generator.Element) throws -> T) rethrows -> T }
30. KNOW THE BASIC FUNCTIONS extension CollectionType { func map<T>(transform: (Element) -> T) -> [T] func filter(includeElement: (Element) -> Bool) -> [Element] func reduce<T>(initial: T, combine: (T, Element) -> T) -> T }
31. KNOW THE BASIC FUNCTIONS extension SequenceType { func flatMap<S : SequenceType>(transform: (Self.Generator.Element) throws -> S) rethrows -> [S.Generator.Element] }
32. KNOW THE BASIC FUNCTIONS extension SequenceType { func flatMap<S : SequenceType>(transform: (Self.Element) -> S) -> [S.Element] }
33. PROFIT!
34. (SMALL) EXAMPLES OF PROFIT MAPPING struct MyDataModel { // Values } struct MyViewModel { private let model: MyDataModel // Presentation stuff } let models: [MyDataModel] //Read from somewhere let viewModels = models.map(MyViewModel.init)
35. (SMALL) EXAMPLES OF PROFIT struct User { let name: String let nickname: String? } struct UserViewModel { var displayName: String { func formatNickName(nickName: String) -> String { return "Known as \(nickName)" } return self.user.nickname.map(formatNickName) ?? "" } private let user: User }
36. (SMALL) EXAMPLES OF PROFIT REDUCE INSTEAD OF LOOPS let anySubViewEmpty: Bool = self.subviews.reduce(false) { empty, view return empty || CGRectEqualToRect(view.frame, CGRectZero) }
37. (SMALL) EXAMPLES OF PROFIT FLATMAP WITH OPTIONALS struct MyDataModel { // Values } extension MyDataModel { init?(json: JSON) { // Parsing } } let jsonItems: [JSON] // Fetched from a remote server let dataModels = jsonItems.flatMap(MyDataModel.init)
38. ABUSING IT MAP INSTEAD OF LOOPS let views: [UIView] // No readability gain views.map { self.addSubview($0) } // Conveys purpose for view in views { self.addSubview(view) }
39. BEYOND BASICS
40. SEE NEXT TALK FUNCTIONS, A LOVE AFFAIR @JOSHABER
41. !
42. MIXING FP AND OOP VALUE TYPES AND SIDE EFFECTS FUTURES FRP: HTTP://REACTIVEX.IO
43. SEE Intro to FP in Swift: http://harlankellaway.com/blog/2015/08/10/ swift-functional-programming-intro/ Boundaries: https://www.destroyallsoftware.com/talks/boundaries Railway oriented programming: https://vimeo.com/97344498
44. SEE I have no idea what I’m doing: https://realm.io/news/altconf-graham-lee-i-have-no-idea-what-i-m- doing/ Simple made easy: http://www.infoq.com/presentations/Simple-Made-Easy
45. There is no such thing as a best solution, be it a tool, a language, or an operating system. — The pragmatic programmer