Kotlin Types and compatibility with Java

Transcript

1. SwiftΤϯδχΞʹ঺հ͢Δ
   KotlinͷܕͱJavaͱͷޓ׵ੑ
   Swift/Kotlin߹ಉษڧձ #2
   

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2. ࣗݾ঺հ
   

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3. ΘΓ͔ΜΛݱۚͰਫ਼ࢉ͠ͳͯ͘΋ޙ͔ΒεϚϗ্Ͱ੥ٻͨ͠Γग़དྷΔ
   ΞϓϦͩΑʂΘΓ͔Μ(ۉ౳ׂ)͡Όͳͯ͘΋࢖͑ΔΑʂϥϯνͱ͔ʂ
   Android൛͸΄΅KotlinͰ࣮૷͞Ε͍ͯΔΑʂ
   

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4. Kotlinʹ͍͓ͭͯ͞Β͍
   

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5. Swiftͱಉ͘͡Nullڐ༰ܕͱ
   ඇڐ༰ܕ͕͋Δ
   • ѻ͍ํ͸͍͍ͩͨಉ͡
   var str1: String = “hallo”
   str1 = null // ίϯύΠϧΤϥʔ
   var str2: String? = “konichiwa”
   str2 = null
   str2.length // ίϯύΠϧΤϥʔ
   str2?.length
   

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6. Swiftͱಉ͘͡جຊతʹ
   Πϛϡʔλϒϧͳ஋Λ࢖༻͢Δ
   • ѻ͍ํ͸͍͍ͩͨಉ͡
   var str1 = “konichiwa”
   str1 = “hallo”
   val str2 = “konichiwa”
   str2 = “hallo” // ίϯύΠϧΤϥʔ
   

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7. ϓϦϛςΟϒܕͱࢀরܕ
   (ΦϒδΣΫτ)Λ۠ผ͠ͳ͍
   • Javaʹ͸ϓϦϛςΟϒܕͱΦϒδΣΫτͱͯ͠ѻ
   ͏ͨΊͷϥούʔΫϥε͕͕͋ͬͨɺKotlinͰ͸۠
   ผ͠ͳ͍
   • int(Integer) → Int
   • long(Long) → Long
   • boolean(Boolean) → Boolean
   

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8. ίϨΫγϣϯ΋ෆมͱՄมʹ
   ෼͔Ε͍ͯΔ
   • σϑΥϧτͷίϨΫγϣϯ͸ෆม
   • ૢ࡞͍ͨ͠৔߹͸MutableListͳͲΛ࢖͏
   val list = listOf(“a”, “b”, “c”)
   list.add(“d”) // ίϯύΠϧΤϥʔʂ(add()΍remove()ϝιου͸࢖͑ͳ͍)
   val mList = mutableListOf(“a”, “b”, “c”)
   mList.add(“d”)
   

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9. KotlinͷίϨΫγϣϯ֓ཁ
   $PMMFDUJPO .VUBCMF$PMMFDUJPO
   -JTU .VUBCMF-JTU
   

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10. ͱ͜ΖͰɺKotlin͸Javaͱ
    ׬શʹޓ׵ੑ͕͋Γ·͢
    

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12. Java͔ΒݟͨNullඇڐ༰ܕ
    • KotlinͷNullඇڐ༰ܕ͸JavaͰ͸@NotNullΞ
    ϊςʔγϣϯʹͳΔ
    fun getStr(str: String): String {
    return str
    }
    ↓
    @NotNull
    public String getStr(@NotNull String str) {
    Intrinsics.checkParameterIsNotNull(str, "str");
    return str;
    }
    

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13. Kotlin͔ΒݟͨJavaม਺
    • JavaͰఆٛ͞Εͨ஋ΛKotlin͔Βࢀর͢Δͱϓ
    ϥοτϑΥʔϜܕͱ͍͏ಛघͳܕʹͳΔ
    public String getStr(String str) {
    return str;
    }
    ↓
    fun getStr(str: String!): String! {
    return str
    }
    

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14. ϓϥοτϑΥʔϜܕʁ
    • String!ͷΑ͏ʹදݱ͞ΕΔܕ
    • Nullڐ༰ܕ͔ඇڐ༰ܕ͔ෆ໌ͳঢ়ଶ
    • Ξϯϥοϓ͠ͳͯ͘΋ͦͷ··ࢀরͰ͖Δ
    • ࣮ͨͩ͠ߦ࣌ʹNullPointerException͕ൃੜ͠͏Δ
    • JavaଆͰ@Nullable΍@NotNull͕෇͍͍ͯΕ͹ਖ਼͍͠ܕʹม׵͞ΕΔ
    • ͪͳΈʹintͳͲͷϓϦϛςΟϒܕ͸nullʹͳΓ͑ͳ͍ͷͰৗʹඇڐ༰
    ܕͱͯ͠ѻ͑Δ
    

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15. ͳͥϓϥοτϑΥʔϜܕʁ
    • ΋ͱ΋ͱ͸JavaͰఆٛ͞Εͨ஋͸͢΂ͯNullableܕ
    ͱͯ͠ѻ͏Ҋ΋͋ͬͨ
    • ͔ͦ͠͠ΕͰ͸JavaͷϥΠϒϥϦΛࢀরͨ͠৔߹ͳ
    Ͳʹίʔυ͕?ͩΒ͚ʹͳͬͯ͠·͍ݱ࣮తͰ͸ͳ͍
    • ݱ࣮తͳརศੑΛॏࢹ͠ɺϓϥοτϑΥʔϜܕΛɹ
    ఆٛͨ͠
    

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16. Java͔ΒݟͨKotlinίϨΫγϣϯ
    • KotlinͷList΍MutableList͸Java͔Β͸
    java.util.Listʹݟ͑Δ
    fun getList(list: List): List {
    return list
    }
    ↓
    @NotNull
    public List getList(@NotNull List list) {
    Intrinsics.checkParameterIsNotNull(list, "list");
    return list;
    }
    

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17. Java͔ΒݟͨKotlinίϨΫγϣϯ
    • JavaͷίϨΫγϣϯͱKotlinͷίϨΫγϣϯ͸
    ޓ׵ੑ͕͋Γಛʹҙࣝ͢Δ͜ͱͳ͘ѻ͏ࣄ͕
    Ͱ͖Δ
    • ͨͩ͠KotlinͰ͸ෆมͰએݴ͞Ε͍ͯΔίϨΫ
    γϣϯͰ΋Java͔Β͸มߋͰ͖ͯ͠·͏
    

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18. Kotlin͔ΒݟͨJavaίϨΫγϣϯ
    • JavaͷList͸Kotlin͔Β͸MutableͳListͱͯ͠
    ͦͷ··ѻ͑Δ
    • ListΛฦ͢JavaͷϝιουΛoverride͢Δ৔߹
    ͳͲ͸MutableͳListͱͯ͠΋Immutableͳ
    Listͱͯ͠΋ఆٛग़དྷΔ
    

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19. KotlinͷίϨΫγϣϯ֓ཁ
    $PMMFDUJPO .VUBCMF$PMMFDUJPO
    -JTU .VUBCMF-JTU
    "SSBZ-JTU
    

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20. Java͔ΒݟͨIntܕ
    • جຊతʹ͸intʹม׵͞ΕΔ
    • ͨͩ͠ɺInt?ܕ΍Arrayܕ(഑ྻ)ͳͲ͸Φ
    ϒδΣΫτͱͯ͠ѻ͏ඞཁ͕͋ΔͨΊɺ
    Integerܕͱͯ͠ѻΘΕΔ
    

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21. Kotlin͔ΒݟͨϦςϥϧ
    • ٯʹKotlin͔ΒݟͨJavaͷϦςϥϧ͸IntͳͲ
    ͷKotlinͷΦϒδΣΫτͱͯ͠ѻΘΕΔ
    

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22. ·ͱΊ
    • Kotlin͸JavaͷΫϥεͱҧ࿨ײͳ͘ڞଘͰ͖Δ
    ࣄΛڧ͘ҙࣝͨ͠ݴޠ࢓༷ʹͳ͍ͬͯΔ
    • ݱ࣮తͳ։ൃݱ৔ͰͷརศੑΛॏࢹͨ͠ࣄ͕
    Kotlin͕ਓؾݴޠʹͳͬͨཧ༝ͷҰ͔ͭ΋͠Ε
    ͳ͍
    

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23. Kotlinͷ࢓༷Λ΋ͬͱ஌Γͨ͘ͳͬ
    ͨΒʮKotlin in Actionʯ͕Φεεϝ
    ࠓճ࿩ͨ͠Α͏ͳ಺༰͕ͱͯ΋෼͔Γ΍͘͢ղ
    આ͞Ε͍ͯ·͢ʂ
    

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