ͨͷ͍͠Kotlin1.1 10෼πΞʔ @kirimin

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What's New in Kotlin 1.1? https://kotlinlang.org/docs/reference/whatsnew11.html

Bound callable references

Bound callable references 1.0·Ͱ͸ؔ਺΍Ҿ਺ࣗ਎ͷϝιουΛؔ਺ࢀরͱͯ͠࢖༻ग़དྷ·͠ ͕ͨɺ1.1Ͱ͸ଞͷม਺ͷϝιουΛؔ਺ࢀরͱͯ͠࢖༻Ͱ͖ΔΑ͏ ʹͳΓ·ͨ͠ɻ

Bound callable references val numbers = listOf("abc", "123", "456")
 
 // 1.1Ͱग़དྷΔΑ͏ʹͳͬͨ͜ͱɹଞͷม਺ͷؔ਺ࢀর
 val numberRegex = "\\d+".toRegex()
 numbers.filter(numberRegex::matches)
 // 1.0Ͱ΋ग़དྷͨ͜ͱୡ fun isAbc(str: String) = str.equals("abc", true)
 numbers.filter(::isAbc)
 numbers.map(String::toUpperCase)
 numbers.filter { numberRegex.matches(it) }

Sealed and data classes

Sealed and data classes SealedΫϥεͷαϒΫϥε͸SealedΫϥεͷΠϯφʔΫϥεͱͯ͠ ͚ͩͰ͸ͳ͘ɺಉҰϑΝΠϧ಺ʹฒྻʹఆٛ͢Δ͜ͱ΋ग़དྷΔΑ͏ ʹͳΓ·ͨ͠ɻ ·ͨɺdataΫϥε͸ࠓ·Ͱ͸ଞͷΫϥεΛܧঝ͢Δ͜ͱ͕ग़དྷ·ͤΜ Ͱ͕ͨ͠ɺ͜Ε΋ՄೳʹͳΓ·ͨ͠ɻ

Sealed and data classes sealed class Express
 
 // ExpressͷαϒΫϥεΛExpressͱฒྻʹએݴ
 class Const(val number: Double) : Express()
 
 // dataΫϥε͸ଞͷΫϥεΛܧঝ͕Մೳʹ // sealedΫϥεͷαϒΫϥεʹ΋ग़དྷ·͢
 data class Sum(val e1: Express, val e2: Express) : Express()

Destructuring Declarations

Destructuring Declarations Destructuring Declarations(෼ղએݴ)͕ϥϜμࣜͷҾ਺Ͱ΋࢖༻ग़དྷΔ Α͏ʹͳΓ·ͨ͠ɻ KotlinͰ͸Pair΍MapͳͲΛval (a, b) = pairͷΑ͏ʹෳ਺ͷม਺ͱͯ͠ એݴ͢Δࣄ͕ग़དྷ·͕͢ɺ1.1Ͱ͸ϥϜμͷҾ਺Λ௚઀(a, b)ͷΑ͏ͳ෼ ׂͨ͠ܗͰهड़͢Δࣄ͕ग़དྷΔΑ͏ʹͳΓ·ͨ͠ɻ

Destructuring Declarations val map = mapOf(1 to "one", 2 to "two")
 // ࠓ·Ͱ͸Ҿ਺ΛҰ౓ड͚͔ͯΒ෼ׂએݴ͢Δඞཁ͕͋ͬͨ
 map.map { entry ->
 val (key, value) = entry
 "$key -> $value!"
 }
 
 // 1.1Ͱ͸௚઀keyͱvalueΛ෼ׂએݴ͢Δࣄ͕Մೳʹ map.map { (key, value) -> "$key -> $value!" }

Underscores for unused parameters

Underscores for unused parameters ϥϜμͰ࢖༻͠ͳ͍Ҿ਺ΛΞϯμʔείΞͰ໌ࣔ͢Δࣄ͕ग़དྷΔΑ͏ʹ ͳΓ·ͨ͠ɻ

Underscores for unused parameters // key͸࢖༻͠ͳ͍ map.map { (_, value) -> "$value!" }

Underscores in numeric literals

Underscores in numeric literals KotlinͰ΋JavaͷΑ͏ʹ਺஋ϦςϥϧʹΞϯμʔείΞΛڬΜͰ ಡΈ΍͘͢ग़དྷΔΑ͏ʹͳΓ·ͨ͠ɻ

Underscores in numeric literals val oneMillion = 1_000_000
 val hexBytes = 0xFF_EC_DE_5E
 val bytes = 0b11010010_01101001_10010100_10010010

Shorter syntax for properties

Shorter syntax for properties ϓϩύςΟͷܕΛgetter͔Βਪ࿦ͯ͠লུग़དྷΔΑ͏ʹͳΓ·͠ ͨɻ

Shorter syntax for properties data class Person(val name: String, val age: Int) {
 // 1.1Ͱग़དྷΔΑ͏ʹͳͬͨ͜ͱ
 val isAdult get() = age >= 20 // Property type inferred to be 'Boolean'
 
 // 1.0·Ͱ͸ܕએݴ͕ඞཁͩͬͨ
 val isChild : Boolean get() = age < 20
 
 // ͜Ε͸1.0Ͱ΋ਪ࿦ͯ͘͠Εͨ
 val isBaby = age < 5
 }

Inline property accessors

Inline property accessors ϓϩύςΟͷΞΫηαʹ΋inline͕࢖༻ग़དྷΔΑ͏ʹͳΓ·ͨ͠ɻ ϓϩύςΟࣗମʹinlineΛ෇͚ͯ྆ΞΫηαʹinlineΛࢦఆ͢Δࣄ ΋ग़དྷ·͢ɻ

Inline property accessors val List.lastIndex: Int
 inline get() = this.size - 1 inline val List.lastIndex: Int
 get() = this.size - 1

Local delegated properties

Local delegated properties ϩʔΧϧม਺ʹ΋by lazyͳͲͷdelegeted property͕࢖༻ग़དྷ ΔΑ͏ʹͳΓ·ͨ͠ɻ

Local delegated properties val answer by lazy {
 println("Calculating the answer...")
 1 + 1
 }
 if (needAnswer()) { // answer͸͜͜ͰॳΊͯܭࢉ͞ΕΔ
 println("The answer is $answer.") 
 } else { // ͜ͷ৔߹͸answer͸ܭࢉ͞Εͳ͍
 println("Sometimes no answer is the answer...")
 }

Generic enum value access

Generic enum value access EnumΛδΣωϦΫεܕͱͯ͠ѻ͑ΔΑ͏ʹͳΓ·ͨ͠ɻ

Generic enum value access enum class RGB { RED, GREEN, BLUE }
 
 // EnumΛδΣωϦΫεͱͯ͠डऔΓશͯͷ஋ͷnameΛग़ྗ͢Δؔ਺
 inline fun > printAllValues() {
 print(enumValues().joinToString { it.name })
 }
 
 fun printAllRGBColor() {
 printAllValues()
 }

ͦͷଞͷมߋɾৄࡉ͸ ެࣜυΩϡϝϯτͰ https://kotlinlang.org/docs/reference/whatsnew11.html