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
Swift flatMap
Search
USAMI Kosuke
February 28, 2017
Programming
4
1k
Swift flatMap
https://kanmoba.connpass.com/event/51628/
USAMI Kosuke
February 28, 2017
Tweet
Share
More Decks by USAMI Kosuke
See All by USAMI Kosuke
Onsager代数とその周辺 / Onsager algebra tsudoi
usamik26
0
650
Apple HIG 正式名称クイズ結果発表 / HIG Quiz Result
usamik26
0
200
ゆめみ大技林製作委員会の立ち上げの話 / daigirin project
usamik26
0
340
@ViewLoadingプロパティラッパの紹介と自前で実装する方法 / @ViewLoading property wrapper implementation
usamik26
0
500
これからUICollectionViewを実践活用する人のためのガイド / Guide to UICollectionView
usamik26
1
760
Xcodeとの最近の付き合い方のはなし / Approach To Xcode
usamik26
2
690
UICollectionView Compositional Layout
usamik26
0
810
Coding Swift with Visual Studio Code and Docker
usamik26
0
530
Swift Extension for Visual Studio Code
usamik26
2
1.1k
Other Decks in Programming
See All in Programming
Android16 Migration Stories ~Building a Pattern for Android OS upgrades~
reoandroider
0
120
Serena MCPのすすめ
wadakatu
4
1k
CSC305 Lecture 06
javiergs
PRO
0
250
20251016_Rails News ~Rails 8.1の足音を聴く~
morimorihoge
2
480
TFLintカスタムプラグインで始める Terraformコード品質管理
bells17
2
210
Writing Better Go: Lessons from 10 Code Reviews
konradreiche
0
1.3k
XP, Testing and ninja testing ZOZ5
m_seki
3
700
他言語経験者が Golangci-lint を最初のコーディングメンターにした話 / How Golangci-lint Became My First Coding Mentor: A Story from a Polyglot Programmer
uma31
0
200
Railsだからできる 例外業務に禍根を残さない 設定設計パターン
ei_ei_eiichi
0
940
bootcamp2025_バックエンド研修_WebAPIサーバ作成.pdf
geniee_inc
0
110
Introduce Hono CLI
yusukebe
6
2.7k
Foundation Modelsを実装日本語学習アプリを作ってみた!
hypebeans
0
120
Featured
See All Featured
Building Adaptive Systems
keathley
44
2.8k
Gamification - CAS2011
davidbonilla
81
5.5k
CSS Pre-Processors: Stylus, Less & Sass
bermonpainter
359
30k
Unsuck your backbone
ammeep
671
58k
Art, The Web, and Tiny UX
lynnandtonic
303
21k
StorybookのUI Testing Handbookを読んだ
zakiyama
31
6.2k
Building Applications with DynamoDB
mza
96
6.7k
Rebuilding a faster, lazier Slack
samanthasiow
84
9.2k
KATA
mclloyd
PRO
32
15k
[Rails World 2023 - Day 1 Closing Keynote] - The Magic of Rails
eileencodes
37
2.6k
GitHub's CSS Performance
jonrohan
1032
470k
The MySQL Ecosystem @ GitHub 2015
samlambert
251
13k
Transcript
flatMap ͷ USAMI Kosuke Fenrir Inc.
͡Ίʹ • Swi% ͷ flatMap ʹ͍ͭͯ͠·͢ • flatMap ͦͷͷ͍Ζ͍Ζͳݴޠʹ͋Γ·͢
flatMap • Α͘Θ͔Βͳ͍Πϝʔδ͕͋Δʁ • ίʔυ͕ಡΈͮΒ͍ʁ • map ͯ͠ fla'en ͢Δͭʁ
• ؔܕʁ Ϟφυʁ
flatMap • ݸਓతʹɺؾָʹ͍͍͑ͱࢥ͏
Op#onal ͷ flatMap
Op#onal ͷ flatMap • มલ : Optional<T> • มॲཧ :
T -> Optional<U> • flatMap : Optional<T> -> Optional<U> • มલ͕ non-nil ͳΒมॲཧΛద༻͢Δ • มલ͕ nil ͳΒมॲཧΛద༻͠ͳ͍
ྫ • มલ : Optional<String> • มॲཧ : String ->
Optional<Int> : { Int($0) } • string.flatMap { Int($0) } • "123" -> Int("123") -> 123 • "abc" -> Int("abc") -> nil • nil -> nil
nil ͷೖྗΛҙࣝ͠ͳ͍͍ͯ͘ // string Optional ͚ͩͲɾɾɾ let string: String?
= "123" let integer: Int? = string.flatMap { Int($0) // $0 unwrap ͞Ε͍ͯΔ }
if let Ͱॻ͘ͱʹͳΔ let string: String? = "123" let integer:
Int? if let string = string { integer = Int(string) } else { integer = nil }
Op#onal chaining ෩ʹ͏ // Optional chaining string?.isEmpty // ಉ༷ʹ͜Μͳͷ͕ཉ͘͠ͳΔʁ string?.toInt
// ΘΓʹ͜͏͢Δ string.flatMap { Int($0) }
Array ͷ flatMap
Array ͷ flatMap • 2 छྨͷ flatMap ͕ଘࡏ͢Δ
Array ͷ flatMap (1) • มલ : Array<T> • มॲཧ
: T -> Array<U> • flatMap : Array<T> -> Array<U>
ྫ • มલ : Array<Int> • มॲཧ : Int ->
Array<Int> : { [$0, $0 * 10] } • [1, 2, 3].flatMap { [$0, $0 * 10] } • 1 -> [1, 10], 2 -> [2, 20], 3 -> [3, 30] • [1, 10, 2, 20, 3, 30]
Op#onal ͱ Array ͷ flatMap ൺֱ • มલ : Optional<T>
• มॲཧ : T -> Optional<U> • flatMap : Optional<T> -> Optional<U> • มલ : Array<T> • มॲཧ : T -> Array<U> • flatMap : Array<T> -> Array<U>
flatMap ͷجຊܗ • ܕ T U ͕ೖͬͨԿΒ͔ͷശʢBoxʣ͕͋Δͱ͖ʹ • มલ
: Box<T> • มॲཧ : T -> Box<U> • flatMap : Box<T> -> Box<U>
Array ͷ flatMap (2) • มલ : Array<T> • มॲཧ
: T -> Optional<U> • flatMap : Array<T> -> Array<U> • มॲཧͷ݁Ռ͕ non-nil ͷͷ͕ Array ͷཁૉʹͳΔ • มॲཧͷ݁Ռ͕ nil ͷͷࣺͯΒΕΔ
ྫ • มલ : Array<String> • มॲཧ : String ->
Optional<Int> : { Int($0) } • ["123", "abc"].flatMap { Int($0) } • "123" -> 123, "abc" -> nil • [123]
Array ͷ 2 ͭͷ flatMap ͷؔ • flatMap (2)
flatMap (1) Ͱ࣮ݱͰ͖Δ • non-nil Λฦ͢ΘΓʹ1ཁૉͷ Array Λฦ͢ • nil Λฦ͢ΘΓʹۭͷ Array Λฦ͢ • flatMap (2) ͷํ͕ίʔυ͕γϯϓϧʹͳΔ • flatMap (1) ࣮͋Μ·ΓΘͳ͍
׆༻ྫ • ["A", "B", nil, "C"] : [String?] • ͔͜͜Β
nil ΛऔΓআ͍ͨ [String] ͕ཉ͍͠ // flatMap ͳ͠ͳΒɺ͜Μͳײ͡Ͱॻ͘ʁ ["A", "B", nil, "C"] .filter({ $0 != nil }) as! [String]
׆༻ྫ // ୯ʹ͜͏ॻ͚ྑ͍ ["A", "B", nil, "C"].flatMap { $0 }
• มલ : Array<Optional<String>> • มॲཧ : Optional<String> -> Optional<String> • flatMap : Array<Optional<String>> -> Array<String>
flatMap Λ׆༻͢Δ໘ • Op$onal ͱͷ૬ੑ͕ྑ͍ • Op$onal Λѻ͏ॲཧ͕͋Δͱ͖ʹ͑ͳ͍͔ߟ͑Δͱྑ͍
ࢀߟɿଞʹ flatMap ͕͑Δͷ • Result ܕʢan+typical/Resultʣ • Op+onal ͱ΄΅ಉ͡ʢnil ͷΘΓʹ۩ମతͳ
Error Λฦ͢ʣ • Observable ܕʢRxSwi:ʣ • ඇಉظετϦʔϜɺ్தͰΤϥʔʹͳͬͨ߹ͷରԠ͕༰қ
flatMap Λ্खʹ׆༻͠Α͏