こんな時どう書くの？逆引きKotlin入門

by Fukui Atsuko

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͜Μͳ࣌Ͳ͏ॻ͘ͷʁ ٯҾ͖Kotlinೖ໳ 2018/5/30 KotlinѪ޷ձ vol1  Atsuko FUKUI

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Agenda • ࣗݾ঺հ • ຊ೔ͷΰʔϧ • ͜Μͳ࣌Ͳ͏ॻ͘ͷʁٯҾ͖Kotlinೖ໳ • ·ͱΊ

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ࣗݾ঺հ • ෱Ҫರࢠ / Fukui Atsuko • @muumuumuumuu • Android Developer • Mercari, Inc.

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ຊ೔ͷΰʔϧ • ؾܰʹKotlinΛॻ͖࢝ΊΒΕΔΑ͏ʹٯҾ͖ͷ ReferenceΛఏڙ͢Δ • Kotlinॳ৺ऀ޲͚Λ૝ఆ • Kotlin͢Ͱʹॻ͖ͳΕ͍ͯΔਓ͸ʮΘ͔Δʯ ʮKotlin͔Θ͍͍ʯͱࢥ͍ͳ͕Βฉ͍͍ͯͯԼ͞ ͍ • #love_kotlin ͷϋογϡλά͋Γ·͢Αʂ

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͜Μͳ࣌Ͳ͏ॻ͘ͷʁ ٯҾ͖Kotlinೖ໳

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ม਺ͷએݴ(1/3) • val / var म০ࢠͰม਺͕એݴͰ͖Δ • val͸ﬁnal, var͸࠶୅ೖՄ

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ม਺ͷએݴ(2/3) • ܕਪ࿦Λαϙʔτ • Φϓγϣφϧ • ܕͷએݴ࣌ʹ໌ࣔతʹ?Λ͚ͭͳ͍ͱnullΛ ڐ༰͠ͳ͍

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ม਺ͷએݴ(3/3) • Ϋϥεʹଐ͢Δඞཁ͸ͳ͍(= ୈ1ڃΦϒδΣ Ϋτͱͯ͠એݴͰ͖Δ) • ఆ਺ʹ͸const

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ؔ਺ͷએݴ(1/2) • funम০ࢠͰؔ਺͕એݴͰ͖Δ • Ҿ਺ͱ໭Γ஋ͷࢦఆ͸ҎԼͷ௨Γ • த਎͕1ߦͰ͔͚Δ৔߹͸=Ͱܨ͛ͯreturnΛ লུ΋Ͱ͖Δ

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ؔ਺ͷએݴ(2/2) • σϑΥϧτҾ਺ͱ໊લ෇͖Ҿ਺Λαϙʔτ

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৚݅ࣜ if (1/3) • Kotlinʹ͓͍ͯif͸ࣜ(expression) • จ(statement)Ͱ͸ͳ͍ • ͭ·Γ஋Λฦ͢͜ͱ͕Ͱ͖Δ

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৚݅ࣜ if (2/3) • ʢ࢒೦ͳ͕Βʣࡾ߲ԋࢉࢠ͸αϙʔτ͞Εͯ ͍ͳ͍ • ΤϧϏεԋࢉࢠ( ?: )͸αϙʔτ͞Ε͍ͯΔ

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৚݅ࣜ if (3/3) • null νΣοΫ͸είʔϓؔ਺ͱΦϓγϣφϧ ͷ૊Έ߹Θ͕ͤΑ͘࢖ΘΕΔ

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৚݅ࣜ when (1/2) • if ಉ༷ʹwhen΋ࣜ • whenͷޙΖͷ()ͷ஋͕ൺֱͷର৅ʹͳΔ

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৚݅ࣜ when (2/2) • whenͷޙΖͷ() ͸ͳͯ͘΋OK • ൺֱର৅ͷ஋͕ෳ਺͋Δ৔߹ʹศར