Equatable, Comparable and Hashable

by Shigure Shimotori

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Equatable / Comparable / Hashable Λ׬શʹཧղ͢Δ @S_Shimotori Otemachi.swift x Kyobashi.swift #01

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ͩΕ • @S_Shimotori·ͨ͸@S_Shimotori_pub • ֶੜ • DroidKaigi2016-2018ӡӦϝϯόʔ

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iOSDCʹొஃ͠·͢ • #1349ʮARC vs. GCʁARC in GCʁʯ • 5෼ͰGCͷ࿩Λ͠·͢ • ݫ͍͠ • Reject͞Εͨ΍ͭ΋ద౰ʹڙཆ͢Δͭ΋Γ • ςετ • ԋࢉࢠ • Ͳ͜Ͱʁ

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Equatable Comparable Hashable

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͓͞Β͍ • Equatable • ౳͍͔͠Ͳ͏͔ൺֱͰ͖Δ • Comparable • ؔ܎ԋࢉࢠͰൺֱͰ͖Δ • ͍͍ͪͪൺֱ༻ͷؔ਺Λ༻ҙ͠ͳͯ͘΋ιʔτͰ͖Δ • Hashable • ϋογϡ஋Λ࡞ΕΔ • Map/DictionaryͷΩʔʹͳΕΔ • Java͸ComparableͷΈinterfaceͰ࢒Γ͸class Objectʹੜ͑ͯΔ • Python͸duck typing

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SwiftͰ͸:

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EquatableͱΏ͔͍ͳ஥ؒͨͪ(Ұ෦লུ) &RVBUBCMF $PNQBSBCMF )BTIBCMF /VNFSJD 4FU"MHFCSB 4USJEFBCMF 4USJOH1SPUPDPM 3FGFSFODF$POWFSUJCMF Foundation಺ͷࢀরܕ΁ଓ͘ɻ String͕ଓ͘ɻ 1࣍ݩͷ࿈ଓతͳ஋ɻ ਺஋΍UnsafePointer͕ଓ͘ɻ ೋ߲ࢉज़ԋࢉɻ Set͕ଓ͘ɻ • ΋ͬͱ΋ਓؾͳProtocolͷ1ͭ • ͳʹΑΓଘࡏײ͕େ͖͍ɺେ͖͗͢Δ • Equatable.swiftʹ͸ͪΌ͔ͬΓಉҰ൑ఆͷ࣮૷΋͍Δ

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protocol Equatable

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ͱΓ͋͑ͣ == Λ࣮૷͢Ε͹OKʂ ❌

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protocol Equatableͷཁ݅ • ୅ସՄೳੑ • ൓ࣹੑ • ରশੑ • ਪҠੑ • a == b ͕ਅͳΒ not a != b ͕ਅ • ͜ͷ͏ͪEquatable͔ΒϑΥϩʔ͕ೖΔͷ͸࠷ޙ͚ͩʂ • ҙਤతʹΦʔόʔϥΠυ͠ͳ͍ݶΓ==ͷٯͷ݁ՌΛฦ͢

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OptionalͱEquatableͷؔ܎ • Optional͸EquatableͰ͸ͳ͍ • Ͱ΋is Equatableͷ݁Ռ͸த਎ʹґଘ͢Δ • Ͱ΋ผͰԋࢉࢠ͕࣮૷͞Ε͍ͯΔͷͰnilͱͷൺֱ͸Մೳ

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protocol Comparable

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ద౰ʹ < Λ࣮૷͓͚ͯ͠͹ ͳΜͱ͔ͳΔ΍ͭ ❌

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protocol Comparableͷ໾ׂͱཁ݅ • ܕʹࣗવॱং෇͚Λ༩͑Δ • σϑΥϧτͷιʔτํ๏ΛܾΊΔͱ͍͏͜ͱ • Swift͸ؔ܎ԋࢉࢠͰදݱ͍ͯ͠ΔͷͰEquatable͕ඞਢ • ࡶʹ࣮૷͠ͳ͍ݶΓ͸Equatableͱໃ६͠ͳ͍ • ࡶʹ࣮૷͠ͳ͍ݶΓ͸ < = > ͷͲΕ͔1͚͕ͭͩtrueʹͳΔ • strict total orderingͱݺ͹ΕΔੑ࣭Λຬͨ͞ͳ͚Ε͹ͳΒͳ͍ • ʮ͖ͬͪΓϧʔϧΛܾΊͯશһҰྻʹฒ΂ͳ͍ͱͩΊʯ • ුಈখ਺఺਺ͳͲͰྫ֎͕ೝΊΒΕΔ৔߹͕͋Δ

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sort͸2छྨ • Ҿ਺ͳ͠ͷsort / sorted • ࣗવॱং෇͚ʹैͬͯιʔτ͢Δ • ͭ·Γཁૉ͕ComparableͰͳ͚Ε͹ͳΒͳ͍ • Ҿ਺ΛऔΔsort / sorted • ର৅ίϨΫγϣϯ಺ͷΈͰ௨༻͢Δॱং෇͚Ͱιʔτ͢Δ • ཁૉ͕ComparableͰͳͯ͘΋͍͍ • strict weak orderingͳॱং෇͚͕ڐ͞ΕΔ • Comparableͱͷҧ͍͸ൺֱෆೳ͕ڐ͞ΕΔ͜ͱ • ͲͪΒ΋࠷ޙ͸ॱং෇͚ʹैͬͯΠϯτϩιʔτ͞ΕΔ

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protocol Hashable

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ͱΓ͋͑ͣ ϋογϡ஋Λग़͓͚ͯ͠͹OKʂ ❌

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protocol Hashable • ϋογϡΛ࣮૷͢Δͱ͖ͷΑ͋͘Δ஫ҙ • ޓ͍ʹಉ஋ͳΒϋογϡ஋΋౳͘͠ͳ͚Ε͹ͳΒͳ͍ • ٯ͸੒ཱ͠ͳͯ͘΋Α͔ͬͨΓ͢Δ • SwiftͰ͸EquatableඞਢͳͷͰ࣮૷Λ๨ΕΔ͜ͱ͸ͳ͍͸ͣ • ϧʔϧʹଇͬͯͪΌΜͱ࣮૷͢Δ͜ͱʂ

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Ҏ্ʂ

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͓·͚

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assertEqual

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assertEqualʹ͸ݴޠͷݸੑ͕ग़Δ • Javaʹ͸ࢀরܕ༻ͱϓϦϛςΟϒܕ༻͕ͦΕͧΕ༻ҙ͞Ε͍ͯΔ • Pythonʹ͸1छྨ͔͠ͳ͍ • Objective-C͸ΦϒδΣΫτ༻ͱεΧϥ༻͕༻ҙ͞Ε͍ͯΔ • Swift͸NonNull༻ͱNullable༻͕༻ҙ͞Ε͍ͯΔ • ࢀরܕͱ஋ܕͰͷ۠ผͰ͸ͳ͍ • ͜ͷ2ͭ΋΄ͱΜͲҧ͍͕ͳ͍ɺ࣮࣭1छྨɻ

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·ͱΊ

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·ͱΊ • Equatable / Comparable / Hashableʹ͸ϧʔϧ͕͋Δ • ޓ͍ͷؔ܎ੑ͸protocolͷܧঝͰදݱ͞Ε͍ͯΔ͕ɺ ϧʔϧʹଇ͍ͬͯΔ͔Ͳ͏͔͸ݟͯ͘Εͳ͍ ਖ਼࣮͘͠૷͠·͠ΐ͏ʂ ཧ૝Λݴ͑͹ͦͷςετ΋ཉ͘͠ͳ͍ʁ