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doyaaaaaken
April 05, 2021
Programming
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20210404 Kotlin Tech Talk発表『例外ではなくnullを返すKotlinらしいAPIデザイン』
doyaaaaaken
April 05, 2021
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Transcript
ྫ֎Ͱͳ͘nullΛฦ͢ KotlinΒ͍͠APIσβΠϯ Kotlin Tech Talk 2021/04/05 খࢁ݈ଠ(Kenta Koyama) @doyaaaaaaken
ࣗݾհ • ࣄ • גࣜձࣾsmartround ۀϝϯόʔ / CTO • αʔόαΠυKotlinɾVueJSΛࠓΑ͘ॻ͍͍ͯ·͢
• OSS׆ಈ • kotlin-csvͷ࡞ऀʢ⭐: 250ʣ • KtorɾExposedɾkotestͷίϯτϦϏϡʔτ • झຯ • ອըɾήʔϜɾϓϩάϥϛϯάɾάϧϝɾςχεɾϘʔυήʔϜɾຑɾཱྀߦ…etc
͋Δײͨ͡՝ • java.time.LocalDateͷparseϝιου͕͍ͮΒ͍ • LocalDate.parse(dateStr: String): LocalDate • ՝1: yyyy-MM-ddܗࣜͷจࣈྻ͔͠ड͚͚ͳ͍
• ՝2: ྫ֎ͷ߹ʹඋ͑try-catchΛॻ͘ඞཁ͕͋Γ
՝ͷରॲ • จࣈྻΛύʔε͢ΔutilityؔΛ࡞ͬͨ • fun parseLocalDate(dateStr: String): LocalDate? • ՝1:
yyyy-MM-ddܗࣜͷจࣈྻ͔͠ड͚͚ͳ͍ 㱺 ෳͷϑΥʔϚοτΛύʔεՄೳʹɻղܾʂʂ • ՝2: ྫ֎ͷ߹ʹඋ͑try-catchΛॻ͘ඞཁ͕͋Γ 㱺 ྫ֎Ͱͳ͘nullΛฦ͢Α͏ʹɻղܾʂʂ
ίʔυϨϏϡʔ • ࣭༰ • ࣭ɿʰ ྫ֎Ͱͳ͘nullΛฦ͢Α͏ʹͨ͠ͷͳͥʁʱ • ݩʑJavaඪ४ϥΠϒϥϦ͕ྫ֎Λฦ͢ͷཧ༝͕͋ΔͷͰͳ͍͔ʁ • ճ
1. ྫ֎Λฦ͢ඞવੑ͕ͳ͍ͨΊ 2. nullableʹ͢Δઃܭͷ΄͏͕try-catchΛॻ͔ͣʹࡁΈɺίʔυهड़ྔ͕গͳ͘ͳΔ 3. Kotilnͷඪ४ϥΠϒϥϦͱ͔Λݟͯͯɺͪ͜Βͷ΄͏͕KotlinͬΆ͍͔Β
ίʔυϨϏϡʔ • ࣭༰ • ࣭ɿʰ ྫ֎Ͱͳ͘nullΛฦ͢Α͏ʹͨ͠ͷͳͥʁʱ • ݩʑJavaඪ४ϥΠϒϥϦ͕ྫ֎Λฦ͢ͷཧ༝͕͋ΔͷͰͳ͍͔ʁ • ճ
1. ྫ֎Λฦ͢ඞવੑ͕ͳ͍ͨΊ 2. nullableʹ͢Δઃܭͷ΄͏͕try-catchΛॻ͔ͣʹࡁΈɺίʔυهड़ྔ͕গͳ͘ͳΔ 3. Kotilnͷඪ४ϥΠϒϥϦͱ͔Λݟͯͯɺͪ͜Βͷ΄͏͕KotlinͬΆ͍͔Β ओ؍తͳճͳͷͰɺ͏গ͖ͪ͠ΜͱݴޠԽͯ͠આ໌͍ͨ͠ͱײ͍ͯͨ͡
༗ࣝऀͷݟղ • JetbrainsͷKotlin։ൃϦʔυͷਓ͕ॻ͍ͨهࣄ͕ෲམͪ͢Δ༰ͩͬͨ • Kotlin and Exceptions • ཁ •
KotlinΒ͍͠APIσβΠϯͱͯ͠… 1. ϝιουͷฦΓΛnullઐ༻ܕʹ͢Δ͜ͱͰɺϝιουͷৼΔ͍Λදݱ͖͢ 2. ྫ֎༧ظͤ͵ൃੜ࣌ʹ͛ɺͦͷྫ֎ΞϓϦέʔγϣϯͷϧʔτϨϕϧͰHandling͖͢ • JavaϥΠϒϥϦ͕ྫ֎Λฦ͢͜ͱ͕ଟ͍ͷݕࠪྫ֎͕͋Δ͔Β • Kotlinඪ४ϥΠϒϥϦ OrNull ͕͍ͭͨͷ͕ଟ͍ • ྫɿStringܕͷtoIntOrNull, ListܕͷgetOrNull, firstOrNull …
ͦͷଞɿࢀߟهࣄհ • ࠓճͷ༰ͷৄࡉҎԼهࣄʹ·ͱ·͍ͬͯ·͢ • ʰKotlinΒ͍͠APIσβΠϯʹ͢Δʹྫ֎Ͱͳ͘nullΛฦ͢ʱ ※ ଞʹKotlinؔ࿈ͷTipsܥهࣄΛ৭ʑॻ͍ͯ·͢ • ʰKotlinͷlazyʢԆॲཧʣͷΈΛௐͯࣗͰ؆қʹ࣮ͯ͠Έͨʱ •
ʰKotlinͷΫϥεҕৡͷ͍ॴʱ • ʰKotlinʹ͓͚ΔFactoryϝιουͷ࣮ύλʔϯʱ • ʰKotlinͰωετߏͷDSLΛ࣮͢Δํ๏ʱ • ʰܕ҆શʹIDͷܕΛએݴ͢Δ࣮ύλʔϯʢKotlinͷ߹ʣʱ • ʰKotlinͷSequenceͱListͷڍಈͷҧ͍ʹ͍ͭͯʱ
ձࣾએ • smartroundͰΤϯδχΞΛ ઈࢍืू͍ͯ͠·͢ʂʂ • ʰελʔτΞοϓɾࢿՈؒͷσʔλڞ༗ɾཧ ϓϥοτϑΥʔϜʱΛ։ൃ • ελʔτΞοϓ1500ࣾɾࢿՈ100͕ࣾొ •
αʔόαΠυKotlinɾVue.jsɾAWSΛར༻ • ࣾһ10໊ఔͷϑΣʔζͰ͢ ͚ͩฉ͍͍ͨํେܴͳͷͰWantedlyɾTwitter DM͔Β͓ؾܰʹ͝Ԡื͍ͩ͘͞ʂ ࢀߟ63- w αʔϏε-1ϖʔδ w ٕज़հࢿྉʰTNBSUSPVOEΛࢧ͑Δٕज़ʱ w XBOUFEMZ࠾༻ϖʔδ
͝ਗ਼ௌ͋Γ͕ͱ͏͍͟͝·ͨ͠ @doyaaaaaken