Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Finding Happiness in Functional Programming
Search
Brandon Williams
October 01, 2016
Programming
0
610
Finding Happiness in Functional Programming
Video:
https://www.youtube.com/watch?v=A0VaIKK2ijM
Brandon Williams
October 01, 2016
Tweet
Share
More Decks by Brandon Williams
See All by Brandon Williams
Server-Side Swift from Scratch
mbrandonw
4
1.8k
Playground Driven Development
mbrandonw
0
330
Anything You Can Do I Can Do Better
mbrandonw
1
120
The Two Sides of Testing
mbrandonw
1
140
Other Decks in Programming
See All in Programming
Compose Multiplatform × AI で作る、次世代アプリ開発支援ツールの設計と実装
thagikura
0
170
パッケージ設計の黒魔術/Kyoto.go#63
lufia
3
440
スケールする組織の実現に向けた インナーソース育成術 - ISGT2025
teamlab
PRO
2
170
さようなら Date。 ようこそTemporal! 3年間先行利用して得られた知見の共有
8beeeaaat
3
1.5k
Navigation 2 を 3 に移行する(予定)ためにやったこと
yokomii
0
350
テストカバレッジ100%を10年続けて得られた学びと品質
mottyzzz
2
610
JSONataを使ってみよう Step Functionsが楽しくなる実践テクニック #devio2025
dafujii
1
640
Introducing ReActionView: A new ActionView-compatible ERB Engine @ Rails World 2025, Amsterdam
marcoroth
0
710
Kiroで始めるAI-DLC
kaonash
2
630
testingを眺める
matumoto
1
140
Cache Me If You Can
ryunen344
2
4k
AI Agents: How Do They Work and How to Build Them @ Shift 2025
slobodan
0
100
Featured
See All Featured
Six Lessons from altMBA
skipperchong
28
4k
Building a Scalable Design System with Sketch
lauravandoore
462
33k
Designing Dashboards & Data Visualisations in Web Apps
destraynor
231
53k
CSS Pre-Processors: Stylus, Less & Sass
bermonpainter
358
30k
GraphQLとの向き合い方2022年版
quramy
49
14k
The Web Performance Landscape in 2024 [PerfNow 2024]
tammyeverts
9
810
Exploring the Power of Turbo Streams & Action Cable | RailsConf2023
kevinliebholz
34
6k
Why Our Code Smells
bkeepers
PRO
339
57k
Distributed Sagas: A Protocol for Coordinating Microservices
caitiem20
333
22k
Chrome DevTools: State of the Union 2024 - Debugging React & Beyond
addyosmani
7
850
Optimizing for Happiness
mojombo
379
70k
Speed Design
sergeychernyshev
32
1.1k
Transcript
Finding Happiness in Functional Programming
None
Principles that we benefited from
Separation of effects from purity
Isolation of side-effects An expression is said to have a
side-effect if its execution makes an observable change to the outside world.
Isolation of side-effects self.titleLabel.text = user.name
Isolation of side-effects func update(text: String, forLabel: UILabel) { label.text
= text } update(text: user.name, forLabel: self.titleLabel)
Isolation of side-effects self.loginButton.enabled = !self.userTextField.text.isEmpty && !self.passwordTextField.text.isEmpty
Isolation of side-effects func updateLoginButtonEnabled() { self.loginButton.enabled = !self.userTextField.text.isEmpty &&
!self.passwordTextField.text.isEmpty } func emailChanged() { self.updateLoginButtonEnabled() } func passwordChanged() { self.updateLoginButtonEnabled() }
Isolation of side-effects // Pure, functional world let emailChanged: Signal<String,
NoError> let passwordChanged: Signal<String, NoError> let loginButtonEnabled = combineLatest(emailChanged, passwordChanged) .map { !$0.isEmpty && !$1.isEmpty } // Side-effect world loginButtonEnabled.observeNext { [weak self] in self?.loginButtonEnabled.enabled = $0 }
Isolation of side-effects // Pure, functional world let emailChanged: Signal<String,
NoError> let passwordChanged: Signal<String, NoError> let loginButtonEnabled = combineLatest(emailChanged, passwordChanged) .map { !$0.isEmpty && !$1.isEmpty } // Side-effect world self.loginButton.rac.enabled = loginButtonEnabled
Surfacing of co-effects
Surfacing of co-effects ????????????????
Surfacing of co-effects If an effect is a change to
the outside world after executing an expression...
Surfacing of co-effects If an effect is a change to
the outside world after executing an expression... ...then...
Surfacing of co-effects If an effect is a change to
the outside world after executing an expression... ...then... ...a co-effect is the state of the world that the expression needs in order to execute.
Surfacing of co-effects e.g. Dependency Injection
Surfacing of co-effects Dependency Injection func currentUserIsCreator(ofProject project: Project) ->
Bool { return User.currentUser.id == project.creator.id } currentUserIsCreator(ofProject: project) // => true or false
Surfacing of co-effects Dependency Injection func user(_ user: User, isCreatorOfProject:
Project) -> Bool { return user.id == project.creator.id } user(User.currentUser, isCreatorOfProject: project) // => true or false
Surfacing of co-effects References — Colin Barrett — Functional Swift
Conference 2015 — Structure and Interpretation of Swift Programs — The work of Tomas Petricek — Coeffects: A calculus of context-dependent computation — Coeffects: The next big programming challenge
Effect/Co-effect Duality
Code to the interface you wish you had, not the
interface you were given. - Stephen Celis
An interface we were given
An interface we were given Storyboards — Very thick abstraction
layer — Separates code from data — Constantly catching up to what UIKit can do
An interface we wish we had Lenses
An interface we wish we had Lenses struct Project {
let creator: User let id: Int let name: String }
An interface we wish we had Lenses Project.lens.name // =>
Lens<Project, String>
An interface we wish we had Lenses Project.lens.name // =>
Lens<Project, String> Project.lens.name .~ "Advanced Swift" // => Project -> Project
An interface we wish we had Lenses Project.lens.name // =>
Lens<Project, String> Project.lens.name .~ "Advanced Swift" // => Project -> Project project |> Project.lens.name .~ "Advanced Swift"
An interface we wish we had Lenses project |> Project.lens.name
.~ "Advanced Swift" |> Project.lens.creator.name .~ "Chris Eidhof"
An interface we wish we had UIKit Lenses
An interface we wish we had UIKit Lenses UIView.lens.backgroundColor //
=> Lens<UIView, UIColor>
An interface we wish we had UIKit Lenses UIView.lens.backgroundColor //
=> Lens<UIView, UIColor> UIView.lens.backgroundColor .~ .redColor() // => UIView -> UIView
An interface we wish we had UIKit Lenses UIView.lens.backgroundColor //
=> Lens<UIView, UIColor> UIView.lens.backgroundColor .~ .redColor() // => UIView -> UIView view |> UIView.lens.backgroundColor .~ .redColor() |> UIView.lens.layer.cornerRadius .~ 4 |> UIView.lens.layer.masksToBounds .~ true
An interface we wish we had UIKit Lenses func roundedStyle(cornerRadius:
CGFloat) -> (UIView) -> UIView { return UIView.lens.layer.cornerRadius .~ 4 <> UIView.lens.layer.masksToBounds .~ true } view |> roundedStyle(cornerRadius: 4) |> UIView.lens.backgroundColor .~ .redColor()
An interface we wish we had UIKit Lenses let baseButtonStyle
= roundedStyle(cornerRadius: 4) <> UIButton.lens.titleLabel.font .~ UIFont(size: 16) <> UIButton.lens.contentEdgeInsets .~ .init(topBottom: 6, leftRight: 12) let greenButtonStyle = baseButtonStyle <> UIButton.lens.backgroundColor(forState: .Normal) .~ .greenColor()
An interface we wish we had UIKit Lenses let bigButtonStyle
= baseButtonStyle <> UIButton.lens.contentEdgeInsets %~ { .init(top: $0.top * 2, left: $0.left * 2, bottom: $0.bottom * 2, right: $0.right * 2) }
An interface we wish we had UIKit Lenses let baseButtonStyle
= roundedStyle(cornerRadius: 4) <> UIButton.lens.titleLabel.font %~~ { _, button in button.traitCollection.verticalSizeClass == .Compact ? UIFont(size: 12) : UIFont(size: 14) } <> UIButton.lens.contentEdgeInsets .~ .init(topBottom: 6, leftRight: 12)
Principles that we did not benefit so much from: —
D.R.Y. — S.R.P. — S.O.L.I.D. — Objects
The Result
Testing
Test-Driven Development
Test-Driven Bug Fixing
Playground-Driven Development
Screenshot testing
Event Tracking
Event Tracking
Accessibility
Love for UIKit
Be!er working relationship with Product Managers, Designers and Engineers
Finding Happiness in Functional Programming
Finding Happiness in Functional Programming
[email protected]