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5ͰΘ͔Δ Kotlin Contracts
2019/10/01 potatotips #65
twitter.com/kumamo_tone
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• iOS/AndroidΤϯδχΞˏϠϑʔ
• ษڧձӡӦ
• Bonfire iOSɺWWDC Extended ͳͲ
• ϠϑʔLODGEͰͷpotatotips4ճ
۽ຊ ਖ਼ (@kumamo_tone)
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2019.08
Kotlin 1.3.50
2018.10
Kotlin 1.3
2019.?
Kotlin 1.4
όʔδϣϯͷਪҠ
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2019.08
Kotlin 1.3.50
2018.10
Kotlin 1.3
2019.?
Kotlin 1.4
όʔδϣϯͷਪҠ
৽ػೳ$POUSBDUT͕ొ
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2019.08
Kotlin 1.3.50
2018.10
Kotlin 1.3
2019.?
Kotlin 1.4
όʔδϣϯͷਪҠ
·ͩ&YQFSJNFOUBM͕ͩɺ
4UEMJCͰͨ͘͞ΜΘΕ͍ͯΔ
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͍͠ਓͷͨΊͷ
5ͰΘ͔Δ Kotlin Contracts
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• ίϯύΠϥʹ໌ࣔతʹؔͷ;Δ·͍Λڭ͑Δͷ
• ίϯύΠϥͷ੍Λ؇ΊΔ͜ͱ͕Ͱ͖Δ
Contracts ͱ
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• ίϯύΠϥʹ໌ࣔతʹؔͷ;Δ·͍Λڭ͑Δͷ
• ίϯύΠϥͷ੍Λ؇ΊΔ͜ͱ͕Ͱ͖Δ
Contracts ͱ
ίϯύΠϥͷ੍ʁʁʁ
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εϚʔτΩϟετ
fun getString(s: String?): String {
return if (s == null || s.isEmpty()) {
"ۭͩΑ"
} else {
s
}
}
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εϚʔτΩϟετ
fun getString(s: String?): String {
return if (s == null || s.isEmpty()) {
"ۭͩΑ"
} else {
s
}
}
s ίϯύΠϥʹΑͬͯ
String? ͔Β String ʹ
Ωϟετ͞Ε͍ͯΔ
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εϚʔτΩϟετʹͳΒͳ͍ྫ
fun String?.isNullOrEmpty(): Boolean {
return this == null || this.isEmpty()
}
fun getString(s: String?): String {
return if (s.isNullOrEmpty()) {
"ۭͩΑ"
} else {
s
}
}
֦ுؔʹͯ͠Έͨ
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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
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εϚʔτΩϟετʹͳΒͳ͍ྫ
fun String?.isNullOrEmpty(): Boolean {
return this == null || this.isEmpty()
}
fun getString(s: String?): String {
return if (s.isNullOrEmpty()) {
"ۭͩΑ"
} else {
s!!
}
}
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εϚʔτΩϟετʹͳΒͳ͍ྫ
fun String?.isNullOrEmpty(): Boolean {
return this == null || this.isEmpty()
}
fun getString(s: String?): String {
return if (s.isNullOrEmpty()) {
"ۭͩΑ"
} else {
s!!
}
}
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@kotlin.internal.InlineOnly
public inline fun CharSequence?.isNullOrEmpty(): Boolean {
contract {
returns(false) implies (this@isNullOrEmpty != null)
}
return this == null || this.length == 0
}
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@kotlin.internal.InlineOnly
public inline fun CharSequence?.isNullOrEmpty(): Boolean {
contract {
returns(false) implies (this@isNullOrEmpty != null)
}
return this == null || this.length == 0
}
$POUSBDUʰʰܖʱʱ
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ʰ͜ͷ͕ؔGBMTFΛฦ͢ͱ͖ɺ
͜ͷ$IBS4FRVFODFOVMMͰ
ͳ͍͜ͱΛอূ͢Δʂʱ
@kotlin.internal.InlineOnly
public inline fun CharSequence?.isNullOrEmpty(): Boolean {
contract {
returns(false) implies (this@isNullOrEmpty != null)
}
return this == null || this.length == 0
}
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@kotlin.internal.InlineOnly
public inline fun CharSequence?.isNullOrEmpty(): Boolean {
contract {
returns(false) implies (this@isNullOrEmpty != null)
}
return this == null || this.length == 0
}
ʰ͜ͷ͕ؔGBMTFΛฦ͢ͱ͖ɺ
͜ͷ$IBS4FRVFODFOVMMͰ
ͳ͍͜ͱΛอূ͢Δʂʱ
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@kotlin.internal.InlineOnly
public inline fun CharSequence?.isNullOrEmpty(): Boolean {
contract {
returns(false) implies (this@isNullOrEmpty != null)
}
return this == null || this.length == 0
}
Θ͔ͬͨΑʙ
ίϯύΠϥ
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fun getString(s: String?): String {
return if (s.isNullOrEmpty()) {
"ۭͩΑ"
} else {
s
}
} TOVMM͕อূ͞ΕͯΔͷͰ
εϚʔτΩϟετ
͓͍ͯͨ͠Αʙ
ίϯύΠϥ
TPTNBSUʜʜ
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SVO XJUI
BQQMZ
BMTP
είʔϓؔ
࢛ఱԦ
StdlibͰ͔ͭΘΕ͍ͯΔ΄͔ͷྫ
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val answer: Int
run {
answer = 42
}
print(answer)
run (Kotlin 1.2)
ɺଖΕ
ੜ໋ɺӉɺͦͯ͠ສʹ͍ͭͯͷ
ڀۃͷٙͷ͑ʜ
ΫΫΫʜ
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run (Kotlin 1.2)
ͳΜʜͩͱʜ
ʢେৎͩͱࢥ͏Μ͚ͩͲͳʜʣ
ෳճݺΕͨΒ
͋Ϳͳ͍Αʙ
ίϯύΠϥ
$PNQJMFSFSSPS
$BQUVSFEWBMVFTJOJUJBMJ[BUJPO
JTGPSCJEEFOEVFUPQPTTJCMFSFBTTJHONFOU
val answer: Int
run {
answer = 42
}
print(answer)
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@kotlin.internal.InlineOnly
public inline fun T.run(block: T.() -> R) = block()
@kotlin.internal.InlineOnly
public inline fun T.run(block: T.() -> R): R {
contract {
callsInPlace(block, InvocationKind.EXACTLY_ONCE)
}
return block()
}
run (Kotlin 1.3)
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@kotlin.internal.InlineOnly
public inline fun T.run(block: T.() -> R): R {
contract {
callsInPlace(block, InvocationKind.EXACTLY_ONCE)
}
return block()
}
$POUSBDUʰʰܖʱʱ
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@kotlin.internal.InlineOnly
public inline fun T.run(block: T.() -> R): R {
contract {
callsInPlace(block, InvocationKind.EXACTLY_ONCE)
}
return block()
}
ʰ͜ͷϒϩοΫʜ
ʰͨͬͨͷΈඞ࣮ͣߦ͞ΕΔʂʂʱʱ
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@kotlin.internal.InlineOnly
public inline fun T.run(block: T.() -> R): R {
contract {
callsInPlace(block, InvocationKind.EXACTLY_ONCE)
}
return block()
}
Θ͔ͬͨΑʙ
ίϯύΠϥ
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Ұ͔͠ݺΕͳ͍ͳΒ
ॳظԽͯ҆͠શ͔ͩΒɺ
ڐՄ͓͍ͯͨ͠Αʙ
ίϯύΠϥ
TPTNBSUʜʜ
val answer: Int
run {
answer = 42
}
print(answer)
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ݴ༿ʹ͠ͳ͍ͱɺΘΒͳ͍͜ͱ͋Δʢʁʁʁʣ
http://gahag.net/001427-businessman-handshake/
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• Contractsͱ
• Kotlin 1.3 ͰՃ͞ΕͨػೳʢExperimentalʣ
• isNullOrEmpty/run/with/apply/alsoͳͲStdlibͰଟΘΕ͍ͯΔ
• ίϯύΠϥʹ໌ࣔతʹؔͷ;Δ·͍Λڭ͑Δ͜ͱͰɺ
ίϯύΠϥͷ੍Λ؇ΊΔ͜ͱ͕Ͱ͖Δ
·ͱΊ
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• 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