Either in Kotlin

Transcript

1. KotlinͰEither͍ͨ͠
   Keishin Yokomaku (@KeithYokoma) / Giftmall, Inc.
   potatotips #81
   

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2. KotlinͰEither͍ͨ͠
   About me
   ▸ @KeithYokoma
   
   
   ▸ Giftmall, Inc.
   
   
   ▸ Android App Engineer
   
   
   ▸ https://keithyokoma.dev/
   potatotips #81
   2
   

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3. KotlinͰEither͍ͨ͠
   Foo ͔ Bar ͷͲͪΒ͔Λฦؔ͢਺Λ࡞Γ͍ͨ
   3
   data class Foo(val name: String)
   
   
   data class Bar(val name: String)
   
   
   fun getSomething() = if (flag) {
   
   
   Foo("foo")
   
   
   } else {
   
   
   Bar("bar")
   
   
   }
   potatotips #81
   

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4. KotlinͰEither͍ͨ͠
   Foo ͔ Bar ͷͲͪΒ͔Λฦؔ͢਺Λ࡞Γ͍ͨ
   4
   data class Foo(val name: String)
   
   
   data class Bar(val name: String)
   
   
   fun getSomething(): Any = if (flag) {
   
   
   Foo("foo")
   
   
   } else {
   
   
   Bar("bar")
   
   
   }
   
   
   potatotips #81
   

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5. KotlinͰEither͍ͨ͠
   Foo ͔ Bar ͷͲͪΒ͔Λฦؔ͢਺Λ࡞Γ͍ͨ
   5
   data class Foo(val name: String)
   
   
   data class Bar(val name: String)
   
   
   fun getSomething(): Any = if (flag) {
   
   
   Foo("foo")
   
   
   } else {
   
   
   Bar("bar")
   
   
   }
   
   
   😇
   potatotips #81
   

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6. DX Improvements
   ͦ͜Ͱ Either Ͱ͢Α
   ▸ Either
   
   
   ▸ L͔Rͷ͍ͣΕ͔ͷܕʹͳΓ͑Δ஋Λද͢ܕ
   
   
   ▸ ؔ਺ܕͷ Either Ϟφυͷ࣮૷Ͱ Scala ͳͲʹଘࡏ͢Δ
   
   
   ▸ TypeScript Ͱ͸֓೦ΛΑΓ֦ு͠ Union Type ͱͯ͠ఆٛͯ͋͠Δ
   6
   potatotips #81
   

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7. KotlinͰEither͍ͨ͠
   Foo ͔ Bar ͷͲͪΒ͔Λฦؔ͢਺Λ࡞Γ͍ͨ
   7
   data class Foo(val name: String)
   
   
   data class Bar(val name: String)
   
   
   fun getSomething(): Either = if (flag) {
   
   
   Either.Left(Foo("foo"))
   
   
   } else {
   
   
   Either.Right(Bar("bar"))
   
   
   }
   
   
   potatotips #81
   

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8. DX Improvements
   ͦΜͳ΋ͷ͸ Kotlin ͷݴޠ࢓༷΍ඪ४ϥΠϒϥϦʹ͸ͳ͍
   8
   😥
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9. DX Improvements
   arrow-kt to the rescue?
   ▸ Either ͳͲଟ਺ͷؔ਺ܕͷ֓೦Λ࣮૷͍ͯ͠ΔϥΠϒϥϦ
   
   
   ▸ https://arrow-kt.io/
   
   
   ▸ Kotlin Ͱؔ਺ܕϓϩάϥϛϯάΛ͍ͨ͠ͳΒಋೖ͠Α͏
   9
   potatotips #81
   

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10. DX Improvements
    ׬
    10
    potatotips #81
    

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11. DX Improvements
    ׬
    11
    ▸ Ͱ͸ͳ͍
    potatotips #81
    

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12. DX Improvements
    େ͖͗͢Δarrow-kt
    12
    ▸ ؔ਺ܕϓϩάϥϛϯά͸ٻΊ͍ͯͳ͍
    
    
    ▸ Foo ͔ Bar ͷͲͪΒ͔Λฦؔ͢਺Λܕ҆શʹ࡞Γ͍͚ͨͩ
    
    
    ▸ Either ͚ͩͭ·Έ৯͍͍͕ͨ͠ɺarrow-ktΛೖΕͨΒͦΕҎ֎΋ೖͬͯ͘Δ
    
    
    ▸ ࣗ෼Ͱ Either Λ࣮૷ͯ͠΋͍͍͕ɺ΋ͬͱ͔ΜͨΜʹ໨తΛୡ੒Ͱ͖ͳ͍͔
    potatotips #81
    

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13. DX Improvements
    sealed classes to the rescue
    13
    ▸ Kotlinʹ͓͚Δಛผͳந৅Ϋϥεɺ͋Δ͍͸ந৅ΠϯλϑΣʔε
    
    
    ▸ ಉ͡ϑΝΠϧʹ۩৅Ϋϥεɺ࣮૷ΫϥεΛॻ੍͘໿͕͋Δ
    potatotips #81
    

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14. KotlinͰEither͍ͨ͠
    Foo ͔ Bar ͷͲͪΒ͔Λฦؔ͢਺Λ࡞Γ͍ͨ
    14
    data class Foo(val name: String)
    
    
    data class Bar(val name: String)
    
    
    fun getSomething() = if (flag) {
    
    
    Foo("foo")
    
    
    } else {
    
    
    Bar("bar")
    
    
    }
    
    
    potatotips #81
    

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15. KotlinͰEither͍ͨ͠
    Foo ͔ Bar ͷͲͪΒ͔Λฦؔ͢਺Λ࡞Γ͍ͨ
    15
    sealed class Something
    
    
    data class Foo(val name: String) : Something()
    
    
    data class Bar(val name: String) : Something()
    
    
    fun getSomething() = if (flag) {
    
    
    Foo("foo")
    
    
    } else {
    
    
    Bar("bar")
    
    
    }
    
    
    potatotips #81
    

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16. KotlinͰEither͍ͨ͠
    Foo ͔ Bar ͷͲͪΒ͔Λฦؔ͢਺Λ࡞Γ͍ͨ
    16
    sealed class Something
    
    
    data class Foo(val name: String) : Something()
    
    
    data class Bar(val name: String) : Something()
    
    
    fun getSomething(): Something = if (flag) {
    
    
    Foo("foo")
    
    
    } else {
    
    
    Bar("bar")
    
    
    }
    
    
    potatotips #81
    

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17. DX Improvements
    Why sealed classes?
    17
    ▸ ಉ͡ϑΝΠϧʹ۩৅Ϋϥεɺ࣮૷ΫϥεΛॻ੍͘໿
    
    
    ▸ ίϯύΠϧ࣌ʹ͢΂ͯͷ۩৅Ϋϥεɺ࣮૷Ϋϥε͕೺ѲͰ͖Δ
    
    
    ▸ ܕʹΑΔ৚݅෼ذͷ໢ཏੑΛڧ੍Ͱ͖Δ
    
    
    ▸ ௨ৗͷ abstract class ΍ interface ʹ͸ͳ͍ػೳ
    potatotips #81
    

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18. KotlinͰEither͍ͨ͠
    Foo ͔ Bar ͷͲͪΒ͔Λฦؔ͢਺Λ࡞Γ͍ͨ
    18
    sealed class Something
    
    
    data class Foo(val name: String) : Something()
    
    
    data class Bar(val name: String) : Something()
    
    
    fun doSomething() {
    
    
    when (val something: Something = getSomething()) {
    
    
    is Foo -> {}
    
    
    is Bar -> {}
    
    
    }
    
    
    }
    
    
    potatotips #81
    

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19. KotlinͰEither͍ͨ͠
    Foo ͔ Bar ͷͲͪΒ͔Λฦؔ͢਺Λ࡞Γ͍ͨ
    19
    sealed class Something
    
    
    data class Foo(val name: String) : Something()
    
    
    data class Bar(val name: String) : Something()
    
    
    data class Baz(val name: String) : Something()
    
    
    fun doSomething() {
    
    
    when (val something: Something = getSomething()) {
    
    
    is Foo -> {}
    
    
    is Bar -> {}
    
    
    }
    
    
    }
    
    
    potatotips #81
    💥
    

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20. KotlinͰEither͍ͨ͠
    Foo ͔ Bar ͷͲͪΒ͔Λฦؔ͢਺Λ࡞Γ͍ͨ
    20
    sealed class Something
    
    
    data class Foo(val name: String) : Something()
    
    
    data class Bar(val name: String) : Something()
    
    
    data class Baz(val name: String) : Something()
    
    
    fun doSomething() {
    
    
    when (val something: Something = getSomething()) {
    
    
    is Foo -> {}
    
    
    is Bar -> {}
    
    
    is Baz -> {}
    
    
    }
    
    
    }
    
    
    potatotips #81
    👍
    

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21. DX Improvements
    EitherͷಛԽܕ
    21
    ▸ kotlin.Result
    
    
    ▸ Either ͷ͜ͱ
    
    
    ▸ ݁Ռ͕ਖ਼ৗ͔ҟৗ͔Λද͢
    
    
    ▸ Optional
    
    
    ▸ ஋͕ଘࡏ͢Δ͔ଘࡏ͠ͳ͍͔
    
    
    ▸ Scala ͩͱOptionܕʢ࣮ࡍͷ஋͸Some͔Noneʣ
    
    
    ▸ null ҆શ
    potatotips #81
    

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22. DX Improvements
    ͓ΘΓʹ
    22
    ▸ ΍Γ͍ͨ͜ͱ͸ Either ͕ͩඞͣ͠΋ͦͷ··ͷ࣮૷͕ඞཁͱ͸ݶΒͳ͍
    
    
    ▸ sealed classes Ͱ΋े෼දݱͰ͖Δ
    
    
    ▸ sealed classes ͳΒ3Ҏ্ͷܕͷ૊Έ߹Θ͕ͤͰ͖Δ
    
    
    ▸ A or B or C or …
    
    
    ▸ TypeScript ͷ Union Type ͷΑ͏ʹͰ͖Δ
    potatotips #81
    

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23. DX Improvements
    ͓ΘΓʹ
    23
    ▸ ͦΕͰ΋Eitherͷ࣮૷͕΄͘͠ͳΔͱ͖
    
    
    ▸ ֎෦ϥΠϒϥϦͷఆ͍ٛͯ͠ΔܕΛ࢖͏ͱ͖
    potatotips #81
    

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24. KotlinͰEither͍ͨ͠
    Keishin Yokomaku (@KeithYokoma) / Giftmall, Inc.
    potatotips #81
    

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