Dependency Injection in Scala

by Yuki Ishikawa

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Dependency Injection in Scala גࣜձࣾϑΝϯίϛϡχέʔγϣϯζ ੴ઒ ༟थ

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Proﬁle • ϑΝϯίϛೖࣾ4೥໨ • Scalaྺ2೥൒͘Β͍ (લ: Java, Ruby, Perl,PHP, etc.) • nend, nex8, viidleͷ഑৴γεςϜߏஙΛ୲౰ • ࠷ۙ͸ϒϩοΫνΣʔϯͷษڧΛͨ͠Γ ੴ઒ ༟थ Yuki Ishikawa

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Dependency Injection (DI) ͱ͸Կ͔ʁ

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Dependency Injection (DI) ͱ͸Կ͔ʁ ίϯϙʔωϯτؒͷґଘؔ܎ΛϓϩάϥϜͷ ιʔείʔυ͔Βഉআ͠ɺ֎෦ͷઃఆϑΝΠ ϧͳͲͰ஫ೖͰ͖ΔΑ͏ʹ͢Διϑτ΢ΣΞ ύλʔϯͰ͋Δɻ WikipediaΑΓ https://ja.wikipedia.org/wiki/ґଘੑͷ஫ೖ

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"E$POUSPMMFS "E4FSWJDF "E4FSWJDF*NQM Dependency Injection (DI) ͱ͸Կ͔ʁ .PEVMF *OKFDUPS AdController: ޿ࠂϦΫΤετͷϋϯυϦϯά AdService: ࠷దͳ޿ࠂͷબग़ϩδοΫ

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Dependency Injection (DI) ͱ͸Կ͔ʁ Manual DIʹΑΔ࣮૷ྫɻDIͷํ๏͸Կछྨ΋ଘࡏ͢Δ

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Dependency Injection (DI) ͱ͸Կ͔ʁ Manual DIʹΑΔ࣮૷ྫɻDIͷํ๏͸Կछྨ΋ଘࡏ͢Δ wiring(഑ઢ)

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Կ͕خ͍͠ͷ?

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Կ͕خ͍͠ͷʁ ‣ ݁߹౓ͷ௿ԼɾίϯϙʔωϯτԽͷଅਐ ‣ ୯ମςετ͕͠΍͘͢ͳΔ

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ScalaͰDI͢Δํ๏

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• MacWire • Guice • Spring • Scaldi • SubCut • Freestyle  (Free Monad & Taggless Final) Pure Scala Library • Manual DI • Cake Pattern • Reader Monad • Free Monad • Tagless Final ScalaͷDIύλʔϯ

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͕࣌ؒ͋·Γແ͍ͷͰ • Manual DI • Cake Pattern • MacWire • Guice ͷ̐छྨΛ঺հ͠·͢ʂ

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Manual DI (Constructor Injection) • ίϯετϥΫλҾ਺Λ࢖ͬͯख࡞ۀͰ഑ઢ • Ұ൪؆୯ʹDI͢Δํ๏

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Manual DI (Constructor Injection) ख࡞ۀͰ഑ઢ͢Δ

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Manual DI (Constructor Injection) ςετ͢Δͱ͖͸ܧঝͯ͠mock/stubͰ্ॻ͖͢Ε͹OK

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Manual DI (Constructor Injection) Pros Cons • Ұ൪खܰʹ࢝ΊΒΕΔํ๏ • Compile-time DI • Pure Scala • ґଘؔ܎͕ଟ͍ͱ഑ઢ࡞ۀ͕ͭΒ͍ খن໛ͷϓϩδΣΫτͳΒManualͰे෼!!

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Cake Pattern • ίϯετϥΫλҾ਺Λ࢖༻͠ͳ͍໘ന͍Ξϓϩʔν ‣ ࣗ෼ܕΞϊςʔγϣϯ΍ܧঝͰDI͢Δ • nendͰ࠾༻͍ͯ͠Δ • આ໌͕೉͍͠

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Cake Pattern ίϯϙʔωϯτΛ࡞੒

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Cake Pattern MixinͰΦϒδΣΫτΛ஫ೖ͢Δ

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Cake Pattern Minimal Cake Pattern υϫϯΰΞΧ΢ϯτγεςϜͰ࠾༻͞Ε͍ͯΔख๏ ʢࣗ෼ܕΞϊςʔγϣϯ͕ొ৔͠ͳ͍ͷͰཧղ͠΍͍͢ʣ https://qiita.com/pab_tech/items/1c0bdbc8a61949891f1f

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Cake Pattern Pros Cons • Compile-time DI • Pure Scala • େྔͷϘΠϥʔϓϨʔτ • ॊೈੑ͕௿͍ ‣ Component͕ΠϯελϯεΛ͔̍ͭ࣋ͯ͠ͳ͍ͷͰɺ2ͭͷಉ͡ ܕʹґଘͰ͖ͳ͍ • ύϑΥʔϚϯεɾίϯύΠϧ࣌ؒʹѱӨڹʁ(ະݕূ)

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MacWire • Scala༻ϥΠϒϥϦ • ϚΫϩͰ഑ઢͯ͘͠ΕΔ • viidleͰ࠾༻͍ͯ͠Δ • Adam Warski͞Μ͕࡞ͬͯΔ ‣ ϒϩάͰScalaͷDIؔ࿈ͷهࣄΛެ։ͯ͠Δ ‣ ࠷ۙ͸sttpͱ͔࡞ͬͯΔ

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MacWire wire͢Δ͚ͩͰɺ͋ͱ͸ϚΫϩ͕΍ͬͯ͘ΕΔ

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MacWire wireSetͰෳ਺ΦϒδΣΫτͷSetԽ͕Մೳ

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MacWire scala-commonͰλά෇͚͕Մೳ (λά෇͚ͨ͘͠ͳ͍৔߹͸Manual DIͱซ༻ͯ͠΋ྑ͍)

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MacWire Pros Cons • ϘΠϥʔϓϨʔτ͕গͳ͍ • Compile-time DI • ϚΫϩ (ڧ͍ͯݴ͑͹)

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Guice • Java༻DIϑϨʔϜϫʔΫ • ҆৺ͷGoogle੡ • ߴػೳͰग़དྷΔࣄ͕ଟ͍ • Runtime DI

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Guice ஫ೖ͍ͤͨ͞ͱ͜Ζʹ @Inject Λ͚ͭΔ

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Guice @ImplementedBy Ͱ࣮૷Λࢦఆ͢Δ or bind Ͱ഑ઢ͢Δ

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Guice @Named, annotatedWithͰλά෇͚΋Մೳ

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Guice @Named, annotatedWithͰλά෇͚΋Մೳ

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Guice ProviderͰॊೈͳDI͕Մೳ

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Guice Pros Cons • ߴػೳͰॊೈੑ͕ߴ͍ • ϘΠϥʔϓϨʔτ͕গͳ͍ • ࣮ߦ࣌ʹ഑ઢΛίϯτϩʔϧͰ͖Δ • JavaͰ࢖ͬͯͨਓʹ͸ೃછΈ΍͍͢ • Runtime DI • ֶशίετ͕ߴ͍

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ͳʹΛ࢖͑͹ྑ͍͔ʁ

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ԿΛ࢖͑͹ྑ͍͔ʁ ͓޷͖ͳͷΛͲ͏ͧ

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͓͢͢Ί • ࠷ॳ͸Manual DI͔Β࢝ΊΔͷ͕Φεεϝ • Compile-time DIΛ࢖ͬͨ΄͏͕҆શ • Guice͸ڽͬͨࣄ͕͍ͨ͠৔߹ʹ