Kotlin入門

スコープ関数の理解をゴールとしたKotlinの入門資料

Transcript

1. Googleެࣜαϙʔτʂ
   Kotlinೖ໳
   @magie_pooh
   αϙʔλʔζKotlinษڧձ #3
   

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2. ࣗݾ঺հ
   ౻ాୖຏ
   @magie_pooh
   @magiepooh
   

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3. FOLIO
   γϦʔζAϥ΢ϯυͰ18ԯԁͷࢿۚௐୡΛ࣮ࢪ͠·͠
   ͨɻ೔ຊॳͷςʔϚ౤ࢿܕΦϯϥΠϯূ݊Λͭ͘Γ·͢ɻ
   

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5. What’s Kotlin?
   

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6. Kotlin
   • Jet Brains ͕࡞ͬͨJVMݴޠ
   • ੩తܕ෇͚ͷΦϒδΣΫτࢦ޲ݴޠ
   • GoogleIOͰAndroidͷ։ൃݴޠͱͯ͠ެࣜαϙʔτ͕ൃද
   • 2012೥ࠒ M1ϦϦʔε
   • 2016೥ 1.0 ϦϦʔε
   • Support JS(Kotlin/JS)
   • LLVM(Kotlin/Native)
   

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7. Kotlin
   • Lambdas
   • Nullable(NonNull)
   • High-Order Functions(Stream)
   • Extension Functions
   

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8. Kotlin
   • Lambdas -> Retrolambda
   • Nullable(NonNull) -> Optional
   • High-Order Functions(Stream) -> StremeAPI,
   RxJava
   • Extension Functions
   

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9. Kotlin
   • Lambdas -> Retrolambda
   • Nullable(NonNull) -> Optional
   • High-Order Functions(Stream) -> StremeAPI,
   RxJava
   • Extension Functions
   

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10. ࠓ೔ͷΰʔϧ
    • είʔϓؔ਺ͷཧղ
    • apply
    • let
    • run
    • with
    

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11. ม਺
    

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12. val num : Int = 1

    var num2 : Int = 2

    

    num = 3 // error

    num2 = 3
    ม਺ͷએݴ
    

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13. val num = 1

    var num2 = 2

    

    num = 3 // error

    num2 = 3
    ม਺ͷએݴ
    

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14. Null҆શ
    var a: String = "abc"

    a = null // => ίϯύΠϧΤϥʔ

    

    var b: String? = "abc"

    b = null // => OK
    

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15. 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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16. 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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17. ؔ਺
    

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18. ؔ਺ͷجຊ
    fun add(x: Int, y: Int): Int {

    return x + y

    }
    

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19. ؔ਺ͷجຊ
    fun add(x: Int, y: Int): Int = x + y
    

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20. ؔ਺ͷجຊ
    fun add(x: Int, y: Int) = x + y
    

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21. ߴ֊ؔ਺
    

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22. ߴ֊ؔ਺
    // body ͱ͍͏໊લͷҾ਺ʹؔ਺ΦϒδΣΫτΛ౉͍ͯ͠Δ

    fun lock(lock: Lock, body: () -> T): T {

    lock.lock()

    try {

    // Ҿ਺Ͱ౉͞Εͨؔ਺ΦϒδΣΫτΛ࣮ߦ͍ͯ͠Δ

    return body()

    } finally {

    lock.unlock()

    }

    }
    

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23. ߴ֊ؔ਺
    // body ͱ͍͏໊લͷҾ਺ʹؔ਺ΦϒδΣΫτΛ౉͍ͯ͠Δ

    fun lock(lock: Lock, body: () -> T): T {

    lock.lock()

    try {

    // Ҿ਺Ͱ౉͞Εͨؔ਺ΦϒδΣΫτΛ࣮ߦ͍ͯ͠Δ

    return body()

    } finally {

    lock.unlock()

    }

    }
    

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24. ϥϜμࣜ
    

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25. ϥϜμࣜ
    max(strings, { a, b -> a.length < b.length })

    max(strings) { a, b -> a.length < b.length }
    

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26. ֦ுؔ਺
    

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27. ֦ுؔ਺
    "hoge".isEmpty()
    

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28. ֦ுؔ਺
    "hoge".isEmpty()
    @kotlin.internal.InlineOnly

    public inline fun CharSequence.isEmpty():
    Boolean = length == 0
    

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29. ֦ுؔ਺
    "hoge".isEmpty()
    @kotlin.internal.InlineOnly

    public inline fun CharSequence.isEmpty():
    Boolean = length == 0
    Ϩγʔό
    

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30. ֦ுؔ਺
    "hoge".isEmpty()
    @kotlin.internal.InlineOnly

    public inline fun CharSequence.isEmpty():
    Boolean = length == 0
    this.length:
    this ͸ϨγʔόΦϒδΣΫτʹରԠ
    

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31. ࿅श໰୊Ͱߟ͑ͯΈΔ
    

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32. 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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33. ౴͑
    

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34. 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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35. 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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36. είʔϓؔ਺
    

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37. είʔϓؔ਺ୡ(ൈ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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38. 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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39. είʔϓؔ਺(run)
    public inline fun T.run(block: T.() -> R): R = block()
    val s = "hoge".run { toUpperCase() }

    println(s) //=> HOGE
    ϨγʔόΦϒδΣΫτʹ͸thisͰΞΫηεՄೳ
    ʢলུ͍ͯ͠Δʣ
    

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40. 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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41. είʔϓؔ਺(with)
    public inline fun with(receiver: T, block: T.() -> R): R =
    receiver.block()
    val s = with("hoge") { toUpperCase() }

    println(s) //=> HOGE
    ֦ுؔ਺Ͱ͸ͳ͍
    

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42. είʔϓؔ਺(with)
    public inline fun with(receiver: T, block: T.() -> R): R =
    receiver.block()
    val s = with("hoge") { toUpperCase() }

    println(s) //=> HOGE
    ϨγʔόΦϒδΣΫτʹ͸thisͰΞΫηεՄೳ
    ʢলུ͍ͯ͠Δʣ
    

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43. είʔϓؔ਺(apply)
    public inline fun T.apply(block: T.() -> Unit): T { block();
    return this }
    val s = "hoge".apply { toUpperCase() }

    println(s) //=> hoge
    ໭Γ஋͸this
    ͭ·ΓɺϨγʔόΦϒδΣΫτࣗ਎
    

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44. 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” ͕ฦ͞ΕΔͷͰ஫ҙ
    

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45. είʔϓؔ਺(apply)
    view.layoutParams = view.layoutParams.apply { height = width / 2 }
    

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46. είʔϓؔ਺(also)
    public inline fun T.also(block: (T) -> Unit): T { block(this);
    return this }
    val s = "hoge".also { it.toUpperCase() }

    println(s) //=> hoge
    ໭Γ஋͸this
    ͭ·ΓɺϨγʔόΦϒδΣΫτࣗ਎
    

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47. είʔϓؔ਺(also)
    public inline fun T.also(block: (T) -> Unit): T { block(this);
    return this }
    val s = "hoge".also { it.toUpperCase() }

    println(s) //=> hoge
    Ҿ਺ͱͯ͠T͕౉ͬͯ͘ΔͨΊɺ
    itͰΞΫηεՄೳ
    

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48. είʔϓؔ਺(let)
    public inline fun T.let(block: (T) -> R): R = block(this)
    val upperCase: String? = foo?.let { it.toUpperCase() }
    

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49. είʔϓؔ਺Λ༻͍ͯɺ
    ઌఔͷ໰୊Λ͞Βʹ؆ܿʹɻ
    

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50. 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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51. 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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52. ͜Ε͔Βͷֶश
    

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53. 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
    • ॿ૸ಡຊʢແྉެ։ͷPDFʣ: https://goo.gl/5vUT7o
    • Kotlinʢ੺΂͜ຊʣ
    

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54. ͜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
    • ॿ૸ಡຊʢແྉެ։ͷPDFʣ: https://goo.gl/5vUT7o
    • Kotlinʢ੺΂͜ຊʣ
    

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