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ࢲʹKotlin͕͍߱Γͨ -AndroidͰͷKotlinҠߦΛݟ͖ͯͨࢹ͔ΒͷKotlin- in ΦλΫ͕KotlinΛ͏ϥΠτχϯάτʔΫΠϕϯτ @kirimin
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ࣗݾհ • @kirimin • AndroidΤϯδχΞ • ݱࡏKotlinͰAndroid։ൃ • Kotlinྺ5͘Β͍ • ۀͰJava͔ΒKotlinҠߦܦݧ͋Γ
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͖ΓΈΜͪΌΜ • όʔνϟϧ༮ঁϓϩάϥϚʔ͖ΓΈΜͪΌ ΜͷϚωʔδϟʔͰ͢ɻ • ͍ΘΏΔVTuberɻ • ϓϩάϥϛϯάΤϯδχΞʹ͍ͭͯͷಈ ըΛߘͨ͠ΓϥΠϒίʔσΟϯά৴Λ ͨ͠Γͯ͠·͢ɻ • νϟϯωϧొΑΖ͘͠Ͷʂ
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ٕज़ॻయͰຊΛग़͠·͢(એ) • ϑϦʔϥϯεͷݟΛ ·ͱΊͨຊͱɺ͖ΓΈ ΜͪΌΜͷϑΝϯϒο Ϋ • ٕज़ॻయ64/14ʂ • ങ͍ʹ͖͍ͯͩ͘͞ʂ
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Kotlinͱࢲ • ·ͩKotlinͷ໊ ͕΄ͱΜͲͳ͔ͬ ͨ2015ॳ಄͔ ΒKotlinਪ͠ • ΅͕͘ॳΊͯ Kotlinʹग़ձͬͨ ͷπΠʔτ
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Kotlinͱࢲ • झຯͷΞϓϦΛKotlinʹϑϧॻ͖͑͢Δ (2015) • ࣄͰKotlinҠߦΛܦݧ(2017) • ࠓϑϧKotlinͷϓϩδΣΫτͰ։ൃ(2018)
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Javaͱൺֱͨ͠Kotlinͷར
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Kotlinͷجૅ(ͬ͘͟Γ) • JVMͰಈ͘Javaશޓݴޠ • ੜ࢈ੑͱཧղ͢͠͞ɺಋೖͷ͢͠͞Λҙࣝͨ͠ݱ࣮ࢤͷݴޠ • ؔܕͷΤοηϯεϞμϯͳݴޠ༷Λ࠾༻ͨ͠Alt Java • Nullڐ༰ܕͱNullඇڐ༰ܕ • valʹΑΔఆએݴ • JavaΑΓؾܰʹ͔ͭ͑ΔศརͳϦετૢ࡞ؔ
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JVMͰಈ͘Javaશޓݴޠ • KotlinͷιʔείʔυJavaόΠτίʔυʹม͞ΕΔ • ͭ·Γ࠷ऴతʹJavaʹͳΔ • JavaͷΫϥεϥΠϒϥϦ͕ී௨ʹ͑Δ • JavaϓϩδΣΫτͰڞଘՄೳ • ٯʹKotlinͰॻ͍ͨίʔυΛJava͔Βݺͼग़͢ޓੑ༻ҙ ͞Ε͍ͯΔ
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ੜ࢈ੑͱཧղ͢͠͞ɺಋೖͷɹɹ ͢͠͞Λҙࣝͨ͠ݱ࣮ࢤͷݴޠ • Kotlinಋೖͷֶ͢͠͞शίετͷ͕͞ڧΈ • Ϟμϯ͚ͩͲγϯϓϧͳݴޠ༷ • ࠷৽ͷJavaܦݧऀSwiftܦݧऀͳΒΩϟονΞοϓ͘͠ͳ͍ • ScalaClojureͳͲʹର͢Δେ͖ͳڧΈ • GradleʹΑΔϏϧυγεςϜ • IntelliJͷެࣜαϙʔτ
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ؔܕͷΤοηϯεϞμϯͳ ݴޠ༷Λ࠾༻ͨ͠Alt Java • ߴ֊ؔ(ؔΛड͚औΔؔ)Πϛϡʔλϒϧ ͳͲؔݴޠతͳΤοηϯεΛऔΓೖΕ͍ͯΔ • Java࠷ۙϥϜμࣜStreamɺOptionalɺϥ ϜμࣜͳͲؔܕతͳϞμϯͳݴޠ༷ΛऔΓ ೖΕ͍ͯΔ͕ɺKotlinݴޠϨϕϧͰαϙʔτ͞ Ε͓ͯΓɺΑΓચ࿅͞Ε͍ͯΔ
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Nullڐ༰ܕͱNullඇڐ༰ܕ • KotlinͰมجຊnullΛڐ༰͠ͳ͍ɻ • nullΛڐ༰͢Δ߹໌ࣔతʹ?Λ͚ܕએݴ ͢Δඞཁ͕͋Δ • JavaͷOptionalͱಉ͡ߟ͑ํ͕ͩɺͪ͜Β ݴޠ༷ͱͯ͠αϙʔτ
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Nullڐ༰ܕͱNullඇڐ༰ܕ var hoge: String = null // ίϯύΠϧΤϥʔ var hoge: String = "hoge" hoge = null // ίϯύΠϧΤϥʔ -------------------------------------------- var fuga: String? = null // OK var fuga: String? = "fuga" fuga = null // OK
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NullΛѻ͏ͨΊͷศརͳؔ var hoge: String? = "hoge" hoge.size // ίϯύΠϧΤϥʔ hoge?.size // hoge͕nullͳΒ࣮ߦ͞Εͳ͍ hoge?.size ?: return // hoge͕nullͳΒreturn val size = hoge?.size ?: 0 // hoge͕nullͳΒ0Λೖ hoge?.let { // hoge͕nullͳΒ࣮ߦ͞Εͳ͍ println(it.size) } hoge.isNullOrEmpty() // nullۭ͘͠จࣈͳΒtrue
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valએݴͱvarએݴ • valͰએݴͨ͠มෆม(ఆ)ʹͳΔ • varՄม • KotlinͰग़དྷΔ͚ͩvalΛ͏จԽ
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valએݴͱvarએݴ val hoge: String = "hoge" hoge = "fuga" // ίϯύΠϧΤϥʔ -------------------------------------------- var hoge: String = "hoge" hoge = "fuga" // OK
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JavaΑΓؾܰʹ͔ͭ͑Δศརͳ Ϧετૢ࡞ؔ • KotlinͷCollectionΠϯλʔϑΣʔεʹmap filterͱ͍ͬͨͨ͘͞Μͷؔܕతͳศརϝ ιου͕ఆٛ͞Ε͍ͯΔ • JavaͷStreamͷΑ͏ͳͷ͕ͩɺΑΓؾܰʹ forจͳͲͷΘΓʹ͑Δ
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JavaΑΓؾܰʹ͔ͭ͑Δศརͳ Ϧετૢ࡞ؔ val list = listof("a", "bb", "ccc") val sizeList = list.map { str -> str.size } // sizeList = { 1, 2, 3 } val filteredList = list.filter { str -> str != "bb" } // filteredList = { "a", "ccc" }
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Java͔ΒKotlinͷҠߦ
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Java͔ΒKotlinͷҠߦ • KotlinͱJavaڞੜͰ͖Δ • 1Ϋϥε͔ΒҠߦΛ࢝ΊΒΕΔ • (࠶)JavaͷϥΠϒϥϦϑϨʔϜϫʔΫجຊKotlin Ͱ͑Δ • IntelliJʹϑΝΠϧΛJava͔ΒKotlinʹࣗಈมͯ͠ ͘ΕΔػೳ͕͋Δ
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Java͔ΒKotlinҠߦͯ͠ਏ͔ͬ ͨ • AndroidͰ΄ͱΜͲฉ͍ͨ͜ͱ͕ͳ͍ • ֶशίετ͘Javaͱൺϋʔυϧ͕ߴ͍ͱ͍͏ ͜ͱ͋·Γͳ͍ • KotlinͱJava͕ڞଘ͍ͯ͠ΔϓϩδΣΫτͨ͘͞ Μ͋Δ • Ή͠ΖҰKotlinʹ׳ΕΔͱJavaʹΕͳ͘ͳΔ
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·ͱΊ • Kotlinݱ࣮ࢤָ͔͍ͭ͠ݴޠ • AndroidͷੈքͰKotlinҠߦͷ͍͍͢͝ ͰਐΜͰ͍Δ • όοΫΤϯυͷੈքͰKotlin͕ελϯμʔυ ʹͳΔϙςϯγϟϧଟ͍ʹ͋Δͱࢥ͍ͬͯΔ
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͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠ʂ