Kotlin Coroutines ことはじめ

Kotlin Coroutines の基本や仕組みの話です。
Android での話を中心にしてますが、Kotlinが動く環境ならほぼ同じなので、Android以外のKotlin開発者の方も参考になるかと思います。

2019/11/30 Android 研究＆発表会登壇資料
https://arap.connpass.com/event/153097/ #arap_osaka

1. Kotlin Coroutines ͜ͱ͸͡Ί
2. ࣗݾ঺հ • w ழມ
   ॆԝ
   ͍ͷ·ͨ
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   WFJO
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 J04"OESPJE
   εϚϗΞϓϦΤϯδχΞɻ
 3Y͕޷͖Ͱ͢ɻ
   w QSJWBUF
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   !JOP
   
3. ࠓ೔ͷ࿩ • Kotlinίϧʔνϯͷجຊͱ࢓૊ΈΛ஌Ζ͏
4. ҰൠతʹɺCoroutine ͱ͸ • தஅɾ࠶։͕Մೳͳαϒϧʔνϯ • ฒߦੑ(Concurrent)Λఏڙ͢Δ
5. αϒϧʔνϯʹී௨ͷؔ਺(ͳͲ) αϒϧʔνϯ ؔ਺ͳͲ ॲཧ ॲཧ ॲཧ ʜ SFUVSO
   l)FMMP
   8PSMEl ϝΠϯॲཧ αϒϧʔνϯ։࢝
   
   ʜ αϒϧʔνϯऴྃ
6. ίϧʔνϯʹதஅՄೳͳαϒϧʔνϯ ίϧʔνϯ ॲཧ ZJFME
   lIFMMPz ॲཧ ZJFME
   lXPSMEz ॲཧ ʜ ϝΠϯॲཧ ίϧʔνϯ։࢝
   
   ʜ ίϧʔνϯऴྃ
7. ίϧʔνϯ͸ ฒߦ(Concurrent)ʹಈ࡞͢Δ εϨου" ίϧʔνϯ
    ίϧʔνϯ
    ίϧʔνϯ
    ίϧʔνϯ
    εϨου# ίϧʔνϯ
    ίϧʔνϯ
    ίϧʔνϯ
    ίϧʔνϯ
   
8. ฒߦ(Concurrent) ͱ ฒྻ(Parallel) • ฒߦ(Concurrent) ͷྫ: Coroutine • ฒྻ(Parallel) ͷྫ: ϚϧνεϨουɾϚϧνϓ ϩηε
9. ฒߦ(Concurrent) != ฒྻ(Parallel) εϨου" ίϧʔνϯ
    ίϧʔνϯ
    ίϧʔνϯ
    ίϧʔνϯ
    ͜Ε͸ฒߦͰ͋ͬͯ
 ฒྻͰ͸ͳ͍ ͜Ε͸ฒߦͰ΋
 ฒྻͰ΋͋Δ εϨου# εϨου" ίϧʔνϯ
    ίϧʔνϯ
   
10. Coroutines 
 are 
 light-weight.
11. Kotlin Coroutines
12. Kotlin Coroutine ͷΩϞ • Suspending Function • Structured concurrency • CoroutineContext • Async as Sync
13. Kotlin CoroutineͷΩϞᶃ
 Suspending Function
14. Suspending Function • Kotlin Coroutines ͸ɺίϧʔνϯͷதஅͰ͖ Δੑ࣭Λ suspend ؔ਺(Suspending Function)Ͱ࣮ݱ͍ͯ͠Δɻ
15. Suspending Function ͷੑ࣭ • suspend ؔ਺͸ଞͷ suspend ؔ਺ͷதͰ͔͠ ࣮ߦͰ͖ͳ͍ɻ • ࢠͷ suspend ؔ਺͕தஅ͢Δͱɺ਌ͷ suspend ؔ਺΋ࢭ·Δɻ • suspend ؔ਺ͷதͰී௨ͷؔ਺(suspendͰͳ ͍ؔ਺)ΛݺͿ͜ͱ͸Ͱ͖Δɻ
16. Hello world to Kotlin Coroutine
17. ͜ͷαϯϓϧͰ࢖͍ͬͯΔؔ਺ • ίϧʔνϯϏϧμʔ(ੜ੒ؔ਺): • runBlocking<T> { ... } • CoroutineScope#launch { ... } • suspendؔ਺:
 delay(timeMillis: Long) ※஫: runBlocking͸ཚ༻NGɻ
 ɹɹAndroid؀ڥͰ͸࢖Θͳ͍͜ͱʂ
18. Android ൛
19. CoroutineScopeΫϥε • ίϧʔνϯͷੜଘظؒΛ؅ཧ͢ΔΦϒδΣΫτɻ • MainScope ... UIεϨουͰಈ࡞͢Δείʔϓɻ 
 → AndroidͷActivity ͳͲͱඥ෇͚ͯը໘ͷ
 ɹϥΠϑαΠΫϧͱҰகͤ͞ΒΕΔɻ • GlobalScope ... ΞϓϦͷੜଘظؒͱಉ͡είʔϓɻ
 → όονॲཧͳͲɺΞϓϦੜଘதʹऴΘͬͯ͸ࠔΔॲཧΛ࣮ߦ͢Δɻ
20. αεϖϯυؔ਺ͷྫ • delay (timeMillis: Long) 
 ... ࢦఆϛϦඵ଴ͭɻ • withTimeout<T>(timeMillis: Long) { ... } withTimeoutOrNull<T>(timeMillis: Long) { ...}
 ... ϒϩοΫ಺ͷॲཧ͕ࢦఆϛϦඵΛ௒͑ͨͱ͖ʹ
 ɹλΠϜΞ΢τͤ͞Δɻ • yield() 
 ... ॲཧΛॠஅͯ͠ɺ(͋Ε͹)ଞͷίϧʔνϯʹॲཧΛճ͢ɻ
21. suspend ͸ϊϯϒϩοΩϯά • suspend = தஅ • ͚ͩͲɺεϨουΛϒϩοΫ͠ͳ͍ • →εϨουΛϒϩοΫ͢Δྫ: Thread.sleep()
22. Coroutine ͷ suspend ؔ਺͸ॲཧΛதஅͯ͠ɺ ଞͷฒߦॲཧதͷίϧʔνϯʹεϨουΛৡΔɻ εϨου" ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ZJFME
23. εϨου" ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ZJFME
24. εϨου" ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ZJFME ZJFME ZJFME
25. Suspend Function Ͱ ίϧʔνϯͷதஅͰ͖Δੑ࣭Λ ࣮ݱ͍ͯ͠Δ
26. Kotlin CoroutineͷΩϞᶄ
 Structured Concurrency
27. Structured concurrency ฒߦੑͷߏ଄Խ • ίϧʔνϯ͸਌ࢠؔ܎Λ࣋ͯΔɻ ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
    
28. Α͋͘ΔϚϧνεϨουͳ
 ඇಉظॲཧͷ໰୊ • Ұ෦ͷεϨουΛམͱͨ͠(མͪͨ)ͱ͖ʹɺ
 ࢒ΓͷεϨουΛڠௐͤ͞Δͷ͕େมɻ • λΠϛϯά໰୊ͰσουϩοΫͨ͠Γɺҙਤ͠ͳ ͍ڍಈ͕ى͜Γ΍͍͢ɻ • ໰୊͕ى͖ͨͱ͖ʹݪҼڀ໌ɾσόοά͕೉͠ ͍ɻ
29. ਌ࢠؔ܎ͷ͋Δίϧʔνϯ͸
 ڠௐͤ͞΍͍͢
30. ਌ࢠؔ܎ͷ͋Δίϧʔνϯ͸
 ڠௐͤ͞΍͍͢ ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ΞΫςΟϒͳ ίϧʔνϯ
31. ਌͸ࢠڙͷऴྃΛ଴ͬͯऴྃ͢Δ ΞΫςΟϒͳ ίϧʔνϯ ଴ػதͷ ίϧʔνϯ ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
    
32. ਌ࢠؔ܎ͷ͋Δίϧʔνϯ͸
 ྫ֎ɾΩϟϯηϧ࣌΋ڠௐͤ͞΍͍͢
33. ਌ࢠؔ܎ͷ͋Δίϧʔνϯ͸
 ྫ֎ɾΩϟϯηϧ࣌΋ڠௐͤ͞΍͍͢ ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ྫ֎ൃੜʂ
34. ਌ίϧʔνϯʹྫ֎Λ఻೻ͯ͠
 ίϧʔνϯΛऴྃ͢Δ ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ྫ֎ൃੜʂ ྫ֎εϩʔ ྫ֎εϩʔ
35. ਌ίϧʔνϯ͕ऴྃ͢Δ࣌͸ɺ
 ࢠίϧʔνϯ΋Ωϟϯηϧ͢Δ ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ
     ྫ֎ൃੜʂ KPCDBODFM KPCDBODFM
36. ʹ਌ίϧʔνϯΛࢭΊΕ͹ɺ ࢠίϧʔνϯ΋ࢭ·Δ
37. ਌ࢠϧʔνϯͷείʔϓΛ Ωϟϯηϧ͢Ε͹ɺ ਌ࢠͱ΋Ͳ΋ࢭΊΒΕΔ
38. ίϧʔνϯͷ࣮ߦείʔϓΛ
 Ωϟϯηϧ͢Δ͚ͩͰશ෦ࢭΊΒΕΔ ίϧʔνϯ
     .BJO4DPQF KPCDBODFM "DUJWJUZ PO%FTUSPZ TDPQFDBODFM ίϧʔνϯ
     KPCDBODFM
39. (࠶ܝ) Android Hello world
40. ίϧʔνϯ͸Ͳ͏΍ͬͯ ਌ࢠؔ܎Λ࡞͍ͬͯΔͷ͔ʁ → CoroutineScope
41. launch ͷϥϜμࣜ͸
 this = CoroutineScope
42. ίϧʔνϯ
     .BJO4DPQF KPCDBODFM "DUJWJUZ PO%FTUSPZ TDPQFDBODFM ίϧʔνϯ
     ίϧʔνϯ
     KPCDBODFM (MPCBM4DPQF GlobalScopeͷίϧʔνϯ͸.BJO4DPQFͱؔ܎ͳ͘ಈ͘ʂ launch launch launch
43. Structured Concurrency Λ ׆༻͢Ε͹ ίϧʔνϯ؅ཧָ͕ʹͳΔ
44. Kotlin CoroutineͷΩϞᶅ
 CoroutineContext
45. CoroutineContext %JTQBUDIFS
    
    ɿ
    .BJO +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ͳ͠ ϝΠϯείʔϓͷίϯςΩετ %JTQBUDIFS
    
    ɿ
    .BJO +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ίϧʔνϯ είʔϓ1ͷίϯςΩετ %JTQBUDIFS
    
    ɿ
    .BJO +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ίϧʔνϯ είʔϓͷίϯςΩετ %JTQBUDIFS
    
    ɿ
    %FGBVMU +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ίϧʔνϯ είʔϓͷίϯςΩετ ϝΠϯείʔϓ ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ1ͷείʔϓ είʔϓ ίϧʔνϯͷείʔϓ είʔϓ ίϧʔνϯ
     ίϧʔνϯͷείʔϓ είʔϓ
46. CoroutineContextͷྫ: Job
 ͋Δίϧʔνϯͷ࣮ߦΛද͢Πϯελϯε • ίϧʔνϯΛ࣮ߦ͢ΔͱJobΛ͔͑͢ɻ
47. CoroutineContext %JTQBUDIFS
    
    ɿ
    .BJO +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ͳ͠ ϝΠϯείʔϓͷίϯςΩετ %JTQBUDIFS
    
    ɿ
    .BJO +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ίϧʔνϯ είʔϓ1ͷίϯςΩετ %JTQBUDIFS
    
    ɿ
    .BJO +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ίϧʔνϯ είʔϓͷίϯςΩετ %JTQBUDIFS
    
    ɿ
    %FGBVMU +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ίϧʔνϯ είʔϓͷίϯςΩετ ϝΠϯείʔϓ ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ1ͷείʔϓ είʔϓ ίϧʔνϯͷείʔϓ είʔϓ ίϧʔνϯ
     ίϧʔνϯͷείʔϓ είʔϓ
48. CoroutineContextͷྫ: CorouttineDispatcher
 ίϧʔνϯΛͲͷεϨουͰಈ͔͔͢ΛܾΊΔਓ • Dispatches.Main • Dispatchers.Default • Dispatchers.IO • Dispatchers.Unconfined • ͦͷଞ: newSingleThreadContext("threadName") ͳͲ
49. CoroutineContext %JTQBUDIFS
    
    ɿ
    .BJO +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ͳ͠ ϝΠϯείʔϓͷίϯςΩετ %JTQBUDIFS
    
    ɿ
    .BJO +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ίϧʔνϯ είʔϓ1ͷίϯςΩετ %JTQBUDIFS
    
    ɿ
    .BJO +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ίϧʔνϯ είʔϓͷίϯςΩετ %JTQBUDIFS
    
    ɿ
    %FGBVMU +PC
    
    
    
    
    
    
    
    
    
    
    
    
    ɿ
    ίϧʔνϯ είʔϓͷίϯςΩετ ϝΠϯείʔϓ ίϧʔνϯ
     ίϧʔνϯ
     ίϧʔνϯ1ͷείʔϓ είʔϓ ίϧʔνϯͷείʔϓ είʔϓ ίϧʔνϯ
     ίϧʔνϯͷείʔϓ είʔϓ
50. CoroutinenContextͷྫ:ͦͷଞ • CoroutineName("name") • NonCancellable • CoroutineExceptionHandler {}
51. CoroutineContextͷ࢖͍ํ • ίϧʔνϯϏϧμʔͷҾ਺ʹࢦఆͯ͠࢖͏ • + Ͱ࿈݁ʢॏෳͨ͠ઃఆ͸ӈล༏ઌʣͯ͠૊Έ߹ Θͤͯ࡞Δ
52. CoroutineContextͷ࢖͍ํ • ಉظతʹৼΔ෣ͬͯ͘ΕΔ withContext ͕ศར
53. Kotlin CoroutineͷΩϞᶅ
 Async as Sync
54. TwitterΫϥΠΞϯτతͳ ΞϓϦ࣮૷ΛίϧʔνϯͰߟ͑Δɻ ϩάΠϯ 0, λΠϜϥΠϯऔಘ <
    l͓͸Α͏z lࠓ೔͸ษڧձͰ͢z >
55. ίϧʔνϯ͸ඇಉظ • ྫ: ϩάΠϯͯ͠λΠϜϥΠϯऔಘ͢ΔAPI࣮૷
56. ίϧʔνϯ͸ඇಉظʁ • ඇಉظॲཧΛಉظతͳײ֮Ͱखଓ͖తʹॻ͚Δ
57. ίϧʔνϯ͸ඇಉظॲཧΛಉظ తʢखଓ͖తʣʹॻ͚Δ • ಉظతʹॻ͚ΔͷͰɺ௚ײతͰɺόάΛຒΊࠐΈ ʹ͍͘ɻ(σουϩοΫɾ࣮ߦλΠϛϯά໰୊) • ͳΜͱ͔Listener΍ίʔϧόοΫ஍ࠈ͔Βͷղ์ɻ
58. async / await ΋͋Δ • async ίϧʔνϯͰɺඇಉظίϧʔνϯʹͭͭ͠ɺ ݁ՌΛ଴ͭ͜ͱ΋Ͱ͖Δ • async = ݁ՌΛड͚औΕΔػೳΛ΋ͭ launchɻ
59. Kotlin ίϧʔνϯͷ جຊ͸͜Ε͚ͩ
60. Kotlin Coroutineͷ ศརͳػೳͷ঺հ
61. flow ίϧʔνϯ • flow = γʔέϯεͰॱ࣍݁ՌΛྲྀ͢ async. • Rx ObservableΛࢀߟʹ࡞ΒΕ͍ͯΔɻ • map(transform{}), flatMap,ϑΟϧλ,
 ྫ֎෮ؼॲཧ(catch{}), εϨου੾Γସ͑, combineLatest, zip ͳͲ΋͋Δɻ
62. Channels, produce, actor • Channel<T> ͸ίϧʔνϯؒͷ૒ํ޲ͷσʔ λ΍ΓऔΓʹ͔ͭ͑ΔΦϒδΣΫτɻ • produce<T> { } ... ࢠ͕ૹ৴ͯ͠਌͕ड৴͢Δ Ұํ޲νϟϯωϧΛ࡞Δίϧʔνϯɻ • actor<T> { } ... ਌͕ૹ৴ͯ͠ࢠ͕ड৴͢ΔҰํ ޲νϟωϧΛ࡞Δίϧʔνϯɻ
63. AndroidXͰ࢖͑Δศརͳػೳ • ViewModelScope • LifecycleScope • liveData<T> { LiveDataScope<T> -> Unit ... }: LiveData<T>