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5分でわかる Kotlin Contracts

kumamotone
October 01, 2019

5分でわかる Kotlin Contracts

kumamotone

October 01, 2019
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  1. • iOS/AndroidΤϯδχΞˏϠϑʔ • ษڧձӡӦ • Bonfire iOSɺWWDC Extended ͳͲ •

    ϠϑʔLODGEͰͷpotatotips͸4ճ໨ ۽ຊ ࿨ਖ਼ (@kumamo_tone)
  2. 2019.08 Kotlin 1.3.50 2018.10 Kotlin 1.3 2019.? Kotlin 1.4 όʔδϣϯͷਪҠ

    ·ͩ&YQFSJNFOUBM͕ͩɺ 4UEMJCͰ΋ͨ͘͞Μ࢖ΘΕ͍ͯΔ
  3. εϚʔτΩϟετ fun getString(s: String?): String { return if (s ==

    null || s.isEmpty()) { "ۭͩΑ" } else { s } }
  4. εϚʔτΩϟετ fun getString(s: String?): String { return if (s ==

    null || s.isEmpty()) { "ۭͩΑ" } else { s } } s ͸ίϯύΠϥʹΑͬͯ String? ͔Β String ʹ Ωϟετ͞Ε͍ͯΔ
  5. εϚʔτΩϟετʹͳΒͳ͍ྫ fun String?.isNullOrEmpty(): Boolean { return this == null ||

    this.isEmpty() } fun getString(s: String?): String { return if (s.isNullOrEmpty()) { "ۭͩΑ" } else { s } } ֦ுؔ਺ʹͯ͠Έͨ
  6. εϚʔτΩϟετʹͳΒͳ͍ྫ fun String?.isNullOrEmpty(): Boolean { return this == null ||

    this.isEmpty() } fun getString(s: String?): String { return if (s.isNullOrEmpty()) { "ۭͩΑ" } else { s } } Type mismatch. Required: String Found: String? ίϯύΠϧΤϥʔ
  7. εϚʔτΩϟετʹͳΒͳ͍ྫ fun String?.isNullOrEmpty(): Boolean { return this == null ||

    this.isEmpty() } fun getString(s: String?): String { return if (s.isNullOrEmpty()) { "ۭͩΑ" } else { s!! } }
  8. εϚʔτΩϟετʹͳΒͳ͍ྫ fun String?.isNullOrEmpty(): Boolean { return this == null ||

    this.isEmpty() } fun getString(s: String?): String { return if (s.isNullOrEmpty()) { "ۭͩΑ" } else { s!! } }
  9. @kotlin.internal.InlineOnly public inline fun CharSequence?.isNullOrEmpty(): Boolean { contract { returns(false)

    implies (this@isNullOrEmpty != null) } return this == null || this.length == 0 }
  10. @kotlin.internal.InlineOnly public inline fun CharSequence?.isNullOrEmpty(): Boolean { contract { returns(false)

    implies (this@isNullOrEmpty != null) } return this == null || this.length == 0 } $POUSBDUʰʰܖ໿ʱʱ
  11. @kotlin.internal.InlineOnly public inline fun CharSequence?.isNullOrEmpty(): Boolean { contract { returns(false)

    implies (this@isNullOrEmpty != null) } return this == null || this.length == 0 } ʰ͜ͷؔ਺͕GBMTFΛฦ͢ͱ͖ɺ ͜ͷ$IBS4FRVFODF͸OVMMͰ͸ ͳ͍͜ͱΛอূ͢Δʂʱ
  12. @kotlin.internal.InlineOnly public inline fun CharSequence?.isNullOrEmpty(): Boolean { contract { returns(false)

    implies (this@isNullOrEmpty != null) } return this == null || this.length == 0 } Θ͔ͬͨΑʙ ίϯύΠϥ
  13. fun getString(s: String?): String { return if (s.isNullOrEmpty()) { "ۭͩΑ"

    } else { s } } T͸OVMM͕อূ͞ΕͯΔͷͰ εϚʔτΩϟετ ͓͍ͯͨ͠Αʙ ίϯύΠϥ TPTNBSUʜʜ
  14. val answer: Int run { answer = 42 } print(answer)

    run (Kotlin 1.2) ɺଖΕ͸ ੜ໋ɺӉ஦ɺͦͯ͠ສ෺ʹ͍ͭͯͷ ڀۃͷٙ໰ͷ౴͑ʜ ΫΫΫʜ
  15. @kotlin.internal.InlineOnly public inline fun <T, R> T.run(block: T.() -> R)

    = block() @kotlin.internal.InlineOnly public inline fun <T, R> T.run(block: T.() -> R): R { contract { callsInPlace(block, InvocationKind.EXACTLY_ONCE) } return block() } run (Kotlin 1.3)
  16. @kotlin.internal.InlineOnly public inline fun <T, R> T.run(block: T.() -> R):

    R { contract { callsInPlace(block, InvocationKind.EXACTLY_ONCE) } return block() } $POUSBDUʰʰܖ໿ʱʱ
  17. @kotlin.internal.InlineOnly public inline fun <T, R> T.run(block: T.() -> R):

    R { contract { callsInPlace(block, InvocationKind.EXACTLY_ONCE) } return block() } ʰ͜ͷϒϩοΫ͸ʜ ʰͨͬͨ౓ͷΈඞ࣮ͣߦ͞ΕΔʂʂʱʱ
  18. @kotlin.internal.InlineOnly public inline fun <T, R> T.run(block: T.() -> R):

    R { contract { callsInPlace(block, InvocationKind.EXACTLY_ONCE) } return block() } Θ͔ͬͨΑʙ ίϯύΠϥ
  19. • What’s New in Kotlin 1.3 • https://kotlinlang.org/docs/reference/whatsnew13.html • What's

    new in Kotlin? • https://speakerdeck.com/svtk/whats-new-in-kotlin • վΊֶͯͿContracts • https://speakerdeck.com/tommykw/gai-metexue-hucontracts References