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
Coroutines Flow 入門 / Coroutines Flow Introduction
Search
star_zero
August 05, 2019
Programming
0
360
Coroutines Flow 入門 / Coroutines Flow Introduction
star_zero
August 05, 2019
Tweet
Share
More Decks by star_zero
See All by star_zero
今からはじめるAndroidアプリ開発 2024 / DevFest 2024
star_zero
0
1.4k
Jetpack Compose の Side-effect を使いこなす / DroidKaigi 2023
star_zero
5
6.2k
Android 14 新機能 / Android 14 Meetup Nagoya
star_zero
1
610
Android 14 と Predictive back gesture / Shibuya.apk #42
star_zero
0
400
Coroutines Test 入門 / Android Test Night #8
star_zero
2
1.2k
What's new in Jetpack / I/O Extended Japan 2022
star_zero
1
650
Kotlin 2021 Recap / DevFest 2021
star_zero
3
1.3k
Kotlin Symbol Processing (KSP) を使ったコード生成 / DroidKaigi 2021
star_zero
2
5.2k
What's new Android 12
star_zero
0
570
Other Decks in Programming
See All in Programming
Rubyでやりたい駆動開発 / Ruby driven development
chobishiba
1
740
ソフトウェア品質を数字で捉える技術。事業成長を支えるシステム品質の マネジメント
takuya542
2
14k
AIエージェントはこう育てる - GitHub Copilot Agentとチームの共進化サイクル
koboriakira
0
610
テスト駆動Kaggle
isax1015
1
480
The Evolution of Enterprise Java with Jakarta EE 11 and Beyond
ivargrimstad
0
150
なぜ適用するか、移行して理解するClean Architecture 〜構造を超えて設計を継承する〜 / Why Apply, Migrate and Understand Clean Architecture - Inherit Design Beyond Structure
seike460
PRO
3
780
A full stack side project webapp all in Kotlin (KotlinConf 2025)
dankim
0
130
GitHub Copilot and GitHub Codespaces Hands-on
ymd65536
2
150
脱Riverpod?fqueryで考える、TanStack Queryライクなアーキテクチャの可能性
ostk0069
0
320
PostgreSQLのRow Level SecurityをPHPのORMで扱う Eloquent vs Doctrine #phpcon #track2
77web
2
550
PHPでWebSocketサーバーを実装しよう2025
kubotak
0
300
顧客の画像データをテラバイト単位で配信する 画像サーバを WebP にした際に起こった課題と その対応策 ~継続的な取り組みを添えて~
takutakahashi
1
150
Featured
See All Featured
The Language of Interfaces
destraynor
158
25k
Automating Front-end Workflow
addyosmani
1370
200k
The World Runs on Bad Software
bkeepers
PRO
69
11k
Practical Orchestrator
shlominoach
189
11k
Fantastic passwords and where to find them - at NoRuKo
philnash
51
3.3k
Chrome DevTools: State of the Union 2024 - Debugging React & Beyond
addyosmani
7
740
YesSQL, Process and Tooling at Scale
rocio
173
14k
Intergalactic Javascript Robots from Outer Space
tanoku
271
27k
How to Think Like a Performance Engineer
csswizardry
25
1.7k
Speed Design
sergeychernyshev
32
1k
Making Projects Easy
brettharned
116
6.3k
Reflections from 52 weeks, 52 projects
jeffersonlam
351
21k
Transcript
Coroutines Flow 入門 Kenji Abe
Coroutines Flow とは •雑に言うと、RxJavaみたいなやつ •Cold Stream ‣ 受信しはじめてから動き始める ‣ Hot
Stream は Channel
Coroutines Flow とは • ↓ の資料が分かりやすいので、そっちを見て ‣ https://speakerdeck.com/sys1yagi/5fen- tewakarukotlin-coroutines-flow •この資料では色々な使い方を紹介します
基本的なやつ fun main() = runBlocking { val flow = flow
{ repeat(3) { emit(it) } } flow.collect { println(it) } }
基本的なやつ fun main() = runBlocking { val flow = flow
{ repeat(3) { emit(it) } } flow.collect { println(it) } } Flow builder
基本的なやつ fun main() = runBlocking { val flow = flow
{ repeat(3) { emit(it) } } flow.collect { println(it) } } 値を送出
基本的なやつ fun main() = runBlocking { val flow = flow
{ repeat(3) { emit(it) } } flow.collect { println(it) } } 値を受信
Flow builders •Flow { } •flowOf(...) ‣ flowOf(1, 2, 3)
•(() -> T).asFlow() ‣ ({ 1 }).asFlow()
Intermediate operators •map •filter •take •zip
Flow operators fun main() = runBlocking { val flow =
flowOf(1, 2, 3, 4, 5) flow.map { it * 2 }.collect { println(it) } } 値を2倍
Flow operators fun main() = runBlocking { val flow =
flowOf(1, 2, 3, 4, 5) flow.filter { it % 2 == 0 }.collect { println(it) } } 偶数のみ
Terminal operators •collect •single •reduce •toList
Terminal operators fun main() = runBlocking { val flow =
flowOf(1, 2, 3, 4, 5) val value = flow .filter { it == 5 } .single() println(value) // 5 } 複数の値の場合は例外になる
Terminal operators fun main() = runBlocking { val flow =
flowOf(1, 2, 3, 4, 5) val value = flow .reduce { accumulator, value -> accumulator + value } // 1 + 2 + 3 + 4 + 5 println(value) // 15 }
Terminal operators fun main() = runBlocking { val flow =
flowOf(1, 2, 3, 4, 5) val value = flow .toList() println(value) // [1, 2, 3, 4, 5] }
Change context •flowOn ‣ 上流のContextを変更する ‣ Flowにおいて唯一Contextを切り替える方法 •emitするときにContextが異なると例外
Change context fun main() = runBlocking { val flow =
flowOf(1, 2, 3, 4, 5) flow .map { println("map: ${Thread.currentThread().name}") it + 1 } .flowOn(Dispatchers.IO) .collect { println("collect: ${Thread.currentThread().name}") } } worker main
Change context fun main() = runBlocking { val flow =
flowOf(1, 2, 3, 4, 5) flow .map { } .flowOn(Dispatchers.IO) .filter { } .flowOn(Dispatchers.Default) .map { } .flowOn(Dispatchers.IO) .collect { } }
Change context fun main() = runBlocking { val flow =
flowOf(1, 2, 3, 4, 5) flow .map { } .flowOn(Dispatchers.IO) .flowOn(Dispatchers.Default) .collect { } } 最初のやつが優先
Change context fun main() = runBlocking { val flow =
flow { emit(1) launch { emit(2) } } flow.collect { } } emit時にContextが違うので 例外になる
Exception •catchを使って捕捉できる •上流のストリームの例外のみ捕捉 •onCompletionでfinallyみたいなこともできる
Exception fun main() = runBlocking { flow { } .map
{ } .catch { } .map { } .catch { } .collect { } } ① ② ③ ③の例外はここで捕捉 ①と②の例外はここで捕捉 それ以降は実行されない
Exception fun main() = runBlocking { flow { emit(1) }.catch
{ emit(-1) }.collect { println(it) } } 例外発生時に別の値を送出
Exception fun main() = runBlocking { flow { } .map
{ } .onCompletion { } .map { } .onCompletion { } .collect { } } finallyみたいなやつ
おわり