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Copyright © Sansan, Inc. All rights reserved.
> KotlinでDSL
Jumpei Yamamoto
2016.12.13
第4回 Kotlin勉強会 in Sansan
#kotlin_sansan
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Copyright © Sansan, Inc. All rights reserved.
> ⾃⼰紹介
- ⼭本純平
- Sansan株式会社 Eight事業部
- EightのAndroidアプリの開発
- twitter: @boohbah
- github: https://github.com/yamamotoj
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> Pikkel
• AndroidでIcePickのように状態の保存ができるKotlinの
ライブラリ
• https://github.com/yamamotoj/Pikkel
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> Pikkel
class MainActivity : Activity(), Pikkel by PikkelDelegate() {
var data by state(“”)
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
restoreInstanceState(savedInstanceState)
}
override fun onSaveInstanceState(outState: Bundle?) {
super.onSaveInstanceState(outState)
saveInstanceState(outState)
}
}
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Copyright © Sansan, Inc. All rights reserved. 5
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Copyright © Sansan, Inc. All rights reserved.
> Eight
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Copyright © Sansan, Inc. All rights reserved.
> Agenda
- テーマ：KotlinでDSL
- DSLとは
- KotlinでDSLの実践
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> DSL ドメイン固有⾔語
- Domain Specific Language
- “特定のドメインに集中し、限定された表現⼒
を備えたコンピュータプログラミング⾔語”
by 「ドメイン特化⾔語」マーチン・ファウラー著
- ⼤きく分けて外部DSLと内部DSLがある
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> 外部DSL
- 動作するアプリケーションとは別の独⽴した⾔語
- 独⾃に構⽂解析、字句解析を⾏い、必要な機能を実装す
る。
- 基本的に独⾃の構⽂を持つが、XML等の他の⾔語の構⽂を
利⽤することもある。
CSSの例
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> 内部DSLとは
- アプリケーションの⾔語を 特定のドメイン向けにそれっ
ぽく使う。
- 表現能⼒ （== 読みやすさ）はホスト⾔語の制約に依存
- 「流れるようなインターフェイス」⊂ 内部DSL
- 動的型付⾔語（Rubyとか）と静的型付⾔語（Javaとか
Kotlinとか）で実装の⽅法が異なる
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> 内部DSLの例
- Ruby on rails, rake, gradle
- Anko,
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> 静的型付け⾔語で
> DSLを作る上でのポイント
- 適切にドメインの語彙を使⽤しているか？
- 読み⼿が（余計な複雑さなしに）いかに⾃然に⾔語を読み
下せるか？
- 型付けによって以下に適切にIDEの補完を効かせることが
できるか？
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> JavaのBuilderパターン
People tom = new People.Builder()
.name(“Tom”)
.age(12)
.hobby(“Baseball”)
.build();
tom.hello();
これも⽴派なDSL
new や .Builder()….build()等
ドメインとは無関係の記述が複雑
()とか;とか冗⻑
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Copyright © Sansan, Inc. All rights reserved.
> Kotlin 名前付き引数 / デフォルト引数
class People(
name:String, age:Int, hobby:String = “” )
val tom = People(
age = 12,
name = “tom”
)
引数に名前をつける
ことで、読み⼿がど
の値を設定している
かが⼀⽬瞭然
設定する順番も変え
られる
optionalな項⽬
(hobby)は省略可
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> DSL実践編
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> SMC ( State Machine Compiler)
//State
Start {
// Transition / Next State / Action(s)
TO_ZERO Zero {}
}
Zero {
TO_ONE One {}
}
One {
Return Start {}
}
http://smc.sourceforge.net/
状態遷移をDSL記述してJavaやRubyなどのコードを⽣成
外部DSLとして実装
状態の定義
イベント名
遷移先の状態
アクション
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> DSLを実装する⼿順
- DSLによって実現したいモデル構造（セマンティックモデ
ル）を定義する。
- どういう構⽂を定義するかを考える
- 流れるようなインターフェイス？
- 階層構造
- 構⽂の評価、改善を繰り返す
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> SMC ( State Machine Compiler )
セマンティックモデル
StateMachine
State State State …
Event Event …
Event
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Copyright © Sansan, Inc. All rights reserved.
> Kotlinでモデル構造の定義
class StateMachine(
var currentState: State,
val states: Map)
class State(
val name: String,
val events: Map)
class Event(
val nextState: String,
val action: (()-> Unit)?)
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> SMCの構⽂
//State
// Transition / Next State / Action(s)
Start {
TO_ZERO Zero {}
}
Zero {
TO_ONE One {}
}
One {
Return Start {}
}
可能な限りこれをKotlinで表現してみる
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> Kotlinで定義したSMCの構⽂
val sm = StateMachine.define {
“Start"{
"TO_ZERO" transitTo "Zero" action { }
}
“Zero"{
"TO_ONE" transitTo "One" action { }
}
“One"{
"RETURN" transitTo "Start" action { }
}
}
状態の定義
イベント名 遷移先の状態
アクション
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> Kotlin SMC
val sm = StateMachine.define {
“Start"{
"TO_ZERO" transitTo "Zero" action { }
}
“Zero"{
"TO_ONE" transitTo "One" action { }
}
“One"{
"RETURN" transitTo "Start" action { }
}
}
この構⽂がどのように実装されるか解説していきます。
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Copyright © Sansan, Inc. All rights reserved.
> SMCを実装するクラス構成
StateMachineBuilder
(内部DSLの実装)
StateBuilder
(内部DSLの実装)
EventBuilder
(内部DSLの実装)
1
*
1
*
StateMachine
State
Event
1
*
1
*
build()
build()
build()
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Copyright © Sansan, Inc. All rights reserved.
> StateMachineの定義
val sm = StateMachine.define {
“Start"{
"TO_ZERO" transitTo "Zero" action { }
}
“Zero"{
"TO_ONE" transitTo "One" action { }
}
“One"{
"RETURN" transitTo "Start" action { }
}
}
class StateMachine {
companion object{
fun define(def:StateMachineBuilder.() -> Unit)
: StateMachine { /* … */}
}
}
引数にラムダ式がひとつだけの場合は()を省略可
レシーバー指定の関数型
StateMachineBuilderの拡張関数を引数にとる
StateMachineBuilderにて他のクラスの拡張関数を定義し
ている場合にその拡張関数のスコープを限定することがで
きる
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Copyright © Sansan, Inc. All rights reserved.
> StateMachineBuilderの実装
class StateMachineBuilder {
private val states = mutableMapOf()
private var initialStateName:String? = null
operator fun String.invoke(define: StateBuilder.() -> Unit){
states[this] = StateBuilder(this).apply(define)
if(initialStateName == null){
initialStateName = this
}
}
}
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Copyright © Sansan, Inc. All rights reserved.
> invoke operator
class A {
operator fun invoke(){
print(“this is a”)
}
}
val a = A()
a() // this is a
A()() // this is a
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Copyright © Sansan, Inc. All rights reserved.
> invoke operator
class A {
operator fun invoke( arg: String){
print(“this is a with $arg”)
}
}
val a = A()
a(“foo”) // this is a with foo
A()(“bar”) // this is a with bar
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Copyright © Sansan, Inc. All rights reserved.
> invoke operator
// ֦ுؔͱ࣮ͯ͠
operator fun String.invoke(){
print(“this is $this”)
}
“foo”() // this is foo
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> invoke operator
// ϥϜμࣜΛҾʹͱΔ
operator fun String.invoke(f: String -> Unit){
f(this)
}
“foo”{
print(it)
}
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Copyright © Sansan, Inc. All rights reserved.
> StateMachineBuilderの実装
class StateMachineBuilder {
private val states = mutableMapOf()
private var initialStateName:String? = null
operator fun String.invoke(define: StateBuilder.() -> Unit){
states[this] = StateBuilder(this).apply(define)
if(initialStateName == null){
initialStateName = this
}
}
}
invoke operator Ϩγʔόʔࢦఆͷؔܕ
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> invoke operatorを使った構⽂
val sm = StateMachine.define {
“Start"{
"TO_ZERO" transitTo "Zero" action { }
}
“Zero"{
"TO_ONE" transitTo "One" action { }
}
“One"{
"RETURN" transitTo "Start" action { }
}
}
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> StateBuilderの実装
class StateBuilder(val name:String) {
private val events = mutableMapOf()
infix fun String.transitTo(to:String): EventBuilder {
val eventBuilder = EventBuilder(this, to)
events[this]= eventBuilder
return eventBuilder
}
}
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> 中置関数
class A {
infix fun shows(arg:String){
print(arg)
}
}
val a = A()
a.shows(“bar”)
a shows “bar”
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Copyright © Sansan, Inc. All rights reserved.
> StateBuilderの実装
class StateBuilder(val name:String) {
private val events = mutableMapOf()
infix fun String.transitTo(to:String): EventBuilder {
val eventBuilder = EventBuilder(this, to)
events[this]= eventBuilder
return eventBuilder
}
fun build() = State(name,
events.map { it.key to it.value.build() }.toMap())
}
String型の拡張関数
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> 中置関数を使った構⽂
val sm = StateMachine.define {
“Start"{
"TO_ZERO" transitTo "Zero" action { }
}
“Zero"{
"TO_ONE" transitTo "One" action { }
}
“One"{
"RETURN" transitTo "Start" action { }
}
}
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> EventBuilderの実装
class EventBuilder(val name:String, val transitTo: String){
var action:(()->Unit)? = null
infix fun action(action:()-> Unit){
this.action = action
}
fun build(): Event = Event(transitTo, action)
}
ラムダ式を引数にとる中置関数
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> 中置関数を使った構⽂
val sm = StateMachine.define {
“Start"{
"TO_ZERO" transitTo "Zero" action { }
}
“Zero"{
"TO_ONE" transitTo "One" action { }
}
“One"{
"RETURN" transitTo "Start" action { }
}
}
EventBuilder
中置関数は左結合！
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> Kotlin SMC 完成
val sm = StateMachine.define {
“Start"{
"TO_ZERO" transitTo "Zero" action { }
}
“Zero"{
"TO_ONE" transitTo "One" action { }
}
“One"{
"RETURN" transitTo "Start" action { }
}
}
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Copyright © Sansan, Inc. All rights reserved.
> ソース公開しています。
> https://github.com/yamamotoj/KotlinSMC
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Copyright © Sansan, Inc. All rights reserved.
> KotlinでのDSLの資料
- Anko
- https://github.com/Kotlin/anko
- KotlinでDSLを作るときに活躍する5⼤⾔語機能
@ngsw_taro
- http://taro.hatenablog.jp/entry/
2013/12/25/070324
- KotlinでイケてるDSLを作る @kikuchy
- http://qiita.com/kikuchy/items/
7c8893c4e7e11dafdb6c
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Copyright © Sansan, Inc. All rights reserved.
> Thank you
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