つまらないシステム(2) - Scala 書きやすすぎるFutureの罠

Scalaで詰まらないシステムを作るために覚えていてほしいこと。

Transcript

1. ͭ·Βͳ͍γεςϜ(2) - ॻ͖΍͗͢͢ΔFutureͷ᠘ -
   mashi
   
2. ScalaͷFuture࠷ߴ
   •  ͱʹ͔͘ॻ͖΍͍͢ •  flatMap ͱ for ͷߏจ͕ศར͗͢Δ
   
3. flatMap/for
   •  flatMap Ͱ΋ͦͦ͜͜ॻ͖΍͍͢͠ɺforͰ ॻ͘ͱ͞Βʹॻ͖΍͍͢
   db.getById(id).flatMap { a => db.getByFuga(a.nanikore).flatMap { b => db.updateNanikore(b.piyopiyo).map { c => c.data } } }
   for { a <- db.getById(id) b <- db.getByFuga(a.nanikore) c <- db.updateNanikore(b.piyopiyo) } yield c.data
   ↑ಉ͡↑
   
4. ໰୊఺
   ʊਓਓਓਓਓਓਓਓਓʊ
   ʼɹॻ͖΍͗͢͢Δɹʻ
   ʉY^Y^Y^Y^Y^Y^Y^Y^Yʉ
   ͔͠΋ͦΕͬΆ͘ݟ͑Δ
   
5. ΞΧϯྫ – ඞཁͳ͍flatMap(1)
   •  Ռͨͯ͠
   notification.notify(a, b) ͷԠ౴Λ ଴͔ͬͯΒϨεϙϯεΛฦ͢ҙຯ͕͋Δͷ ͔ʁ
   for { a <- service.getA(id) b <- service.getB(a.name) _ <- notification.notify(a, b) 
   ֎෦αʔϏε΁ͷ௨஌
   } yield b.data
   
6. ΞΧϯྫ – ඞཁͳ͍flatMap
   •  ଴ͭඞཁ͕ͳ͍ɺΤϥʔϋϯυϦϯά͢ Δඞཁ͕ͳ͍ͳΒflatMap͠ͳ͍
   for { a <- service.getA(id) b <- service.getB(a.name) } yield { notification.notify(a, b) 
   ݁ՌΛ଴ͨͳ͍ b.data }
   ˞ notification.notify(a, b) ʹࣦഊͨ͠৔߹ʹFuture.failed ʹ͍ͨ͠৔߹ʹ͸ෆద੾
   मਖ਼ޙ
   
7. •  Ռͨͯ͠
   serviceA.getA ͷ݁ՌΛ଴͔ͬͯ Β
   service.getB Λ࣮ߦ͢Δҙຯ͸͋Δͷ ͔ʁ ΞΧϯྫ – ඞཁͳ͍flatMap(2)
   val id = “randy” for { a <- serviceA.getA(id) b <- serviceB.getB(id)
   } yield a.name + b.name
   
8. •  ͙͢ʹಉ࣌ʹൃՐ͍͍ͯ͠ͳΒͬ͞͞ͱݺ ΜͰ͠·͏ ΞΧϯྫ – ඞཁͳ͍flatMap(2)
   val id = “randy” val aFuture = serviceA.getA(id) val bFuture = serviceB.getB(id) // AͷԠ౴Λ଴͍ͬͯͳ͍ for { a <- aFuture b <- bFuture } yield a.name + b.name
   ˞
   'VUVSF
   ͷ
   [JQ
   ͕ศརʹ࢖͑·͢ɻৄ͘͠͸ௐ΂ͯΈ͍ͯͩ͘͞
   मਖ਼ޙ
   
9. ΞΧϯྫ – DBτϥϯβΫγϣϯԼ
   dbTransaction { implicit tx => for { a <- db.getById(id) tw <- twitterApi.getA(a.name) b <- db.getByFuga(a.nanikore, tw.a) c <- db.updateNanikore(b.piyopiyo) } yield c.data }
   DBτϥϯβΫγϣϯதʹ ΋͔ͨ͠͠Β௕͔͔࣌ؒΔ͔΋͠Εͳ͍͜ͱΛ΍ͬͯ͠·͏
   τϥϯβΫγϣϯ͕͍ͭ·Ͱͨͬͯ΋ऴΘΒͳ͍͔΋͠Εͳ͍͠ɺ ίωΫγϣϯ΋ղ์͞Εͳ͍
   
10. ΞΧϯྫ – DBτϥϯβΫγϣϯԼ
    मਖ਼ྫ
    •  ݪଇτϥϯβΫγϣϯԼͰDBͷૢ࡞Ҏ֎ ͷ͜ͱΛ͠ͳ͍ •  Ͳ͏ͯ͠΋ଞͷ͜ͱΛ͢ΔͳΒλΠϜΞ΢ τΛઃ͚Δ ˞Ͳ͏ͤJDBC͕ϒϩοΩϯάͳͷͰɺԼखʹFutureΛ࢖Θͣී௨ʹॻ͍ͨ΄͏͕ ͍͍͔΋͠Εͳ͍
    
11. ·ͱΊ
    •  Scala ͷ Future + flatMap + forߏจ
    ͸ศར͗͢Δɻ ͙͢ॻ͚Δ •  ͔͠͠Future͑͞࢖͑͹ԿͰ΋ϋΠύϑΥʔϚϯ ε&͍͍ײ͡ʹಈ͘Θ͚Ͱ͸ͳ͍ •  ॻ͍͍ͯΔίʔυ͕͍ͭͲͷΑ͏ʹಈ͘ͷ͔ৗ ʹҙࣝ͢ΔΑ͏ʹ͢Δ –  ౰ͨΓલͷ࿩Ͱ͕͢ɺ׳ΕΔͱଦੑͰॻ͍ͯ͠·͏ͱ ͖͕͋ΔͷͰ…ॳ৺ʹ໭Γ·͠ΐ͏ɻ