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Googleެࣜαϙʔτʂ
Kotlinೖ
@magie_pooh
αϙʔλʔζKotlinษڧձ #3
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ࣗݾհ
౻ాୖຏ
@magie_pooh
@magiepooh
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FOLIO
γϦʔζAϥϯυͰ18ԯԁͷࢿۚௐୡΛ࣮ࢪ͠·͠
ͨɻຊॳͷςʔϚࢿܕΦϯϥΠϯূ݊Λͭ͘Γ·͢ɻ
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No content
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What’s Kotlin?
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Kotlin
• Jet Brains ͕࡞ͬͨJVMݴޠ
• ੩తܕ͚ͷΦϒδΣΫτࢦݴޠ
• GoogleIOͰAndroidͷ։ൃݴޠͱͯ͠ެࣜαϙʔτ͕ൃද
• 2012ࠒ M1ϦϦʔε
• 2016 1.0 ϦϦʔε
• Support JS(Kotlin/JS)
• LLVM(Kotlin/Native)
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Kotlin
• Lambdas
• Nullable(NonNull)
• High-Order Functions(Stream)
• Extension Functions
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Kotlin
• Lambdas -> Retrolambda
• Nullable(NonNull) -> Optional
• High-Order Functions(Stream) -> StremeAPI,
RxJava
• Extension Functions
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Kotlin
• Lambdas -> Retrolambda
• Nullable(NonNull) -> Optional
• High-Order Functions(Stream) -> StremeAPI,
RxJava
• Extension Functions
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ࠓͷΰʔϧ
• είʔϓؔͷཧղ
• apply
• let
• run
• with
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ม
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val num : Int = 1
var num2 : Int = 2
num = 3 // error
num2 = 3
มͷએݴ
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val num = 1
var num2 = 2
num = 3 // error
num2 = 3
มͷએݴ
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Null҆શ
var a: String = "abc"
a = null // => ίϯύΠϧΤϥʔ
var b: String? = "abc"
b = null // => OK
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Null҆શʢݺͼग़͠ʣ
var b: String? = "abc"
val l : Int = b.length // => ίϯύΠϧΤϥʔ
var b: String? = "abc"
val l : Int = if(b != null) {
b.length
} else {
-1
}
val l : Int? = b?.length
val l : Int = b?.length ?: -1
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Null҆શʢΤϧϏεԋࢉࢠʣ
var b: String? = "abc"
val l : Int = if(b != null)
b.length else -1
val l : Int = b?.length ?: -1
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ؔ
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ؔͷجຊ
fun add(x: Int, y: Int): Int {
return x + y
}
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ؔͷجຊ
fun add(x: Int, y: Int): Int = x + y
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ؔͷجຊ
fun add(x: Int, y: Int) = x + y
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ߴ֊ؔ
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ߴ֊ؔ
// body ͱ͍͏໊લͷҾʹؔΦϒδΣΫτΛ͍ͯ͠Δ
fun lock(lock: Lock, body: () -> T): T {
lock.lock()
try {
// ҾͰ͞ΕͨؔΦϒδΣΫτΛ࣮ߦ͍ͯ͠Δ
return body()
} finally {
lock.unlock()
}
}
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ߴ֊ؔ
// body ͱ͍͏໊લͷҾʹؔΦϒδΣΫτΛ͍ͯ͠Δ
fun lock(lock: Lock, body: () -> T): T {
lock.lock()
try {
// ҾͰ͞ΕͨؔΦϒδΣΫτΛ࣮ߦ͍ͯ͠Δ
return body()
} finally {
lock.unlock()
}
}
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ϥϜμࣜ
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ϥϜμࣜ
max(strings, { a, b -> a.length < b.length })
max(strings) { a, b -> a.length < b.length }
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֦ுؔ
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֦ுؔ
"hoge".isEmpty()
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֦ுؔ
"hoge".isEmpty()
@kotlin.internal.InlineOnly
public inline fun CharSequence.isEmpty():
Boolean = length == 0
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֦ுؔ
"hoge".isEmpty()
@kotlin.internal.InlineOnly
public inline fun CharSequence.isEmpty():
Boolean = length == 0
Ϩγʔό
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֦ுؔ
"hoge".isEmpty()
@kotlin.internal.InlineOnly
public inline fun CharSequence.isEmpty():
Boolean = length == 0
this.length:
this ϨγʔόΦϒδΣΫτʹରԠ
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࿅शͰߟ͑ͯΈΔ
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public String toJSON(Collection
collection) {
StringBuilder sb = new StringBuilder();
sb.append("[");
Iterator iterator =
collection.iterator();
while (iterator.hasNext()) {
Integer element = iterator.next();
sb.append(element);
if (iterator.hasNext()) {
sb.append(", ");
}
}
sb.append("]");
return sb.toString();
}
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͑
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fun toJSON(collection: Collection):
String {
val sb = StringBuilder()
sb.append("[")
val iterator = collection.iterator()
while (iterator.hasNext()) {
val element = iterator.next()
sb.append(element)
if (iterator.hasNext()) {
sb.append(", ")
}
}
sb.append("]")
return sb.toString()
}
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public String toJSON(Collection
collection) {
StringBuilder sb = new StringBuilder();
sb.append("[");
Iterator iterator =
collection.iterator();
while (iterator.hasNext()) {
Integer element = iterator.next();
sb.append(element);
if (iterator.hasNext()) {
sb.append(", ");
}
}
sb.append("]");
return sb.toString();
}
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είʔϓؔ
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είʔϓؔୡ(ൈਮ)
public inline fun T.run(block: T.() -> R): R = block()
public inline fun with(receiver: T, block: T.() -> R): R =
receiver.block()
public inline fun T.apply(block: T.() -> Unit): T { block();
return this }
public inline fun T.also(block: (T) -> Unit): T { block(this);
return this }
public inline fun T.let(block: (T) -> R): R = block(this)
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είʔϓؔ(run)
public inline fun T.run(block: T.() -> R): R = block()
val s = "hoge".run { toUpperCase() }
println(s) //=> HOGE
ҙͷܕTΛϨγʔόͱ͠ɺ
ҙͷܕRΛฦؔ͢
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είʔϓؔ(run)
public inline fun T.run(block: T.() -> R): R = block()
val s = "hoge".run { toUpperCase() }
println(s) //=> HOGE
ϨγʔόΦϒδΣΫτʹthisͰΞΫηεՄೳ
ʢলུ͍ͯ͠Δʣ
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είʔϓؔ(with)
public inline fun with(receiver: T, block: T.() -> R): R =
receiver.block()
val s = with("hoge") { this.toUpperCase() }
println(s) //=> HOGE
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είʔϓؔ(with)
public inline fun with(receiver: T, block: T.() -> R): R =
receiver.block()
val s = with("hoge") { toUpperCase() }
println(s) //=> HOGE
֦ுؔͰͳ͍
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είʔϓؔ(with)
public inline fun with(receiver: T, block: T.() -> R): R =
receiver.block()
val s = with("hoge") { toUpperCase() }
println(s) //=> HOGE
ϨγʔόΦϒδΣΫτʹthisͰΞΫηεՄೳ
ʢলུ͍ͯ͠Δʣ
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είʔϓؔ(apply)
public inline fun T.apply(block: T.() -> Unit): T { block();
return this }
val s = "hoge".apply { toUpperCase() }
println(s) //=> hoge
Γthis
ͭ·ΓɺϨγʔόΦϒδΣΫτࣗ
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είʔϓؔ(apply)
public inline fun T.apply(block: T.() -> Unit): T { block();
return this }
val s = "hoge".apply { toUpperCase() }
println(s) //=> hoge
toUpperCase()Λ͍ͯ͠Δ͕ɺ
“hoge” ͕ฦ͞ΕΔͷͰҙ
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είʔϓؔ(apply)
view.layoutParams = view.layoutParams.apply { height = width / 2 }
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είʔϓؔ(also)
public inline fun T.also(block: (T) -> Unit): T { block(this);
return this }
val s = "hoge".also { it.toUpperCase() }
println(s) //=> hoge
Γthis
ͭ·ΓɺϨγʔόΦϒδΣΫτࣗ
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είʔϓؔ(also)
public inline fun T.also(block: (T) -> Unit): T { block(this);
return this }
val s = "hoge".also { it.toUpperCase() }
println(s) //=> hoge
Ҿͱͯ͠T͕ͬͯ͘ΔͨΊɺ
itͰΞΫηεՄೳ
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είʔϓؔ(let)
public inline fun T.let(block: (T) -> R): R = block(this)
val upperCase: String? = foo?.let { it.toUpperCase() }
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είʔϓؔΛ༻͍ͯɺ
ઌఔͷΛ͞Βʹ؆ܿʹɻ
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fun toJSON(collection: Collection):
String {
val sb = StringBuilder()
sb.append("[")
val iterator = collection.iterator()
while (iterator.hasNext()) {
val element = iterator.next()
sb.append(element)
if (iterator.hasNext()) {
sb.append(", ")
}
}
sb.append("]")
return sb.toString()
}
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fun toJSON(collection: Collection):
String =
StringBuilder().run {
append("[")
collection.iterator().also {
while (it.hasNext()) {
append(it.next())
if (it.hasNext()) {
append(", ")
}
}
}
append("]")
toString()
}
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͜Ε͔Βͷֶश
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Next Step
• Slack
• kotlinlang: http://slack.kotlinlang.org/
• kotlinlang-jp: http://kotlinlang-jp.herokuapp.com/
• Try Kotlin: https://try.kotlinlang.org/
• σίϯύΠϧ
• JS, Server: https://github.com/Kotlin/kotlin-fullstack-sample/
• ຊ
• ॿಡຊʢແྉެ։ͷPDFʣ: https://goo.gl/5vUT7o
• Kotlinʢ͜ຊʣ
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͜Ε͔Βͷֶश
• Slack
• kotlinlang: http://slack.kotlinlang.org/
• kotlinlang-jp: http://kotlinlang-jp.herokuapp.com/
• Try Kotlin: https://try.kotlinlang.org/
• σίϯύΠϧ
• JS, Server: https://github.com/Kotlin/kotlin-fullstack-sample/
• ຊ
• ॿಡຊʢແྉެ։ͷPDFʣ: https://goo.gl/5vUT7o
• Kotlinʢ͜ຊʣ