The document discusses Kotlin DSL and how it can be used to create domain-specific languages. It provides examples of using Kotlin features like operators, lambdas, and extensions to build DSLs for validation rules, UI layouts, dependency injection, and more. Key points include how functions, operators, and properties can be overridden or extended to define new syntax and behaviors for DSLs, and how inline functions allow embedding DSL code without additional overhead.

1. Kotlin DSL
~ ~
11/2 2 Android
Kamedon

2. •
• Kotlin
•
•

3. • DSL
• DSL
• DSL
•

4. DSL

5. DSL
• domain-specific language/ )
• DSL
(wikipedia )
•

6. • DSL

7. Builder
//Java
Human human= new Human.Builder()
.setName("Kamedon")
.setAge(30)
.build();
//Kotlin
class Human(val name: String, val age: Int)
Human(age = 30, name = "Kamedon")
if(human.isAdult()){
//成人だったらなにかする
}

8. Build DSL
buildscript {
ext.kotlin_version = '1.2.70'
repositories {
google()
jcenter()
maven {
url 'http://kamedon.github.com/Validation/repository'
}
}
dependencies {
classpath 'com.android.tools.build:gradle:3.1.4'
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:
$kotlin_version"
}
}
•

9. Layout Anko)
verticalLayout {
val name = editText()
button("Say Hello") {
onClick { toast("Hello, ${name.text}!") }
}
}
•
• LinearLayout

10. DI DSL(Kodein)
Kodein {
bind<Presenter>() with singleton {
Presenter(instance(), inetance())
}
}
val presenter: Presenter by instance()
•
•

11. DSL
•
•
• IDE
• Sansan Kotlin DSL

12. DSL
•
•
• Kotlin
Java DSL
• DSL Kotlin

13. DSL

14. • Validation DSL
• DSL
• Validation
https://github.com/kamedon/Validation

16. •
•
[ ]
5 10
[ ]
20
•

18. •
•
•
•

19. DSL

20. DSL (1)
•
• 5
•
• X be Y

21. DSL (2)
•
• 5
• X be Y
not
• X be Y not Message

22. DSL
be not
be not
be not
be not
be not

23. DSL
be not
be not
be not
be not
be not

24. Validation<User> {
"name"{
be { name.isNotBlank() } not "入力してください"
be { name.length >= 5 } not "5文字以上入力"
be { name.length <= 10 } not "10文字以下で入力"
}
"age"{
be { age >= 0 } not "入力してください"
be { age >= 20 } not "20歳以上で入力"
}
}
•

25. DSL

26. • : operator invoke
• {} : lambda lambda
• ()
• : (Extensions Functions or
Properties)
• : infix)
• var val : Builder

27. be
be not
be not

28. DSL
be not
be not
be not
be not
be not

29. be not
be not
be not
be not

30. operator invoke + lambda
Validation<User> {
"name"{
be { name.isNotBlank() } not "入力してください"
be { name.length >= 5 } not "5文字以上入力"
be { name.length <= 10 } not "10文字以下で入力"
}
}
•
class Validation<T> {
companion object {
operator fun <T>
invoke(init: Validation<T>.() -> Unit): Validation<T> {
return Validation<T>().apply(init)
}
}
}

31. + lambda
Validation<User> {
"name"{
be { name.isNotBlank() } not "入力してください"
be { name.length >= 5 } not "5文字以上入力"
be { name.length <= 10 } not "10文字以下で入力"
}
}
•
class Validation<T> {
val validations = mutableMapOf<String, ChildValidation<T>>()
operator fun String.invoke(
init: ChildValidation<T>.() -> Unit
) {
validations.put(this, ChildValidation<T>().apply(init))
}
}

32. infix( )
Validation<User> {
"name"{
be { name.isNotBlank() } not "入力してください"
be { name.length >= 5 } not "5文字以上入力"
be { name.length <= 10 } not "10文字以下で入力"
}
}
•
class ChildValidation<T> {
fun be(f: T.() -> Boolean) = f
infix fun (T.() -> Boolean).not(message: String)
}

33. DSL
Validation<User> {
"name"{
}
}
class Validation<T> {
val validations = mutableMapOf<String, ChildValidation<T>>()
operator fun String.invoke(init: ChildValidation<T>.() -> Unit) {
validations.put(this, ChildValidation<T>().apply(init))
}
companion object {
inline operator fun <T> invoke(
init: Validation<T>.() -> Unit): Validation<T> {
return Validation<T>().apply(init)
}
}
}

34. DSL
be { name.isNotBlank() } not "入力してください"
class ChildValidation<T> {
val validations = mutableListOf<Pair<T.() -> Boolean, String>>()
infix fun be(f: T.() -> Boolean) = f
infix fun (T.() -> Boolean).not(message: String) {
validations.add(Pair(this, message))
}
}
•

35. DSL
Validation<User> {
"name"{
be { name.isNotBlank() } not "入力してください"
be { name.length >= 5 } not "5文字以上入力"
be { name.length <= 10 } not "10文字以下で入力"
}
"age"{
be { age >= 0 } not "入力してください"
be { age >= 20 } not "20歳以上で入力"
}
}
•
validate

36. Validate
class Validation<T> {
val validations = mutableMapOf<String, ChildValidation<T>>()
fun validate(value: T): Map<String, List<String>> {
val messages = mutableMapOf<String, List<String>>()
validations.forEach { map ->
val errors = map.value.validations.asSequence()
.filter { !it.first.invoke(value) }
.map { it.second }
.filter { it.isNotEmpty() }
.toList()
if(errors.isNotEmpty()){
messages.put(map.key, errors)
}
}
return messages
}
}

37. DSL Builder
class Validation<T> {
val validations = mutableMapOf<String, ChildValidation<T>>()
operator fun String.invoke(init: ChildValidation<T>.() -> Unit) {
validations.put(this, ChildValidation<T>().apply(init))
}
companion object {
inline operator fun <T> invoke(
init: Validation<T>.() -> Unit): Validation<T> {
return Validation<T>().apply(init)
}
}
fun validate(value: T): Map<String, List<String>>
}

38. DSL Builder
class ValidationBuilder<T> {
val validations = mutableMapOf<String, ChildValidation<T>>()
operator fun String.invoke(init: ChildValidation<T>.() -> Unit) {
validations.put(this, ChildValidation<T>().apply(init))
}
fun build(): Validation<T> {
return Validation(validations)
}
}
class Validation<T>(val validations: Map<String, ChildValidation<T>>) {
companion object {
inline operator fun <T> invoke(
init: ValidationBuilder<T>.() -> Unit): Validation<T> {
val builder = ValidationBuilder<T>().apply(init)
return builder.build()
}
}
}

39. DSL

40. DSL
•
•
•

42. •
• DSL inline
0

43. inline
class Sample {
fun run(f: () -> Unit) {
f()
}
inline fun inlineRun(f: () -> Unit) {
f()
}
fun main() {
run { print("run") }
inlineRun { print("inlineRun") }
}
}

44. public final class Sample {
public final void run(@NotNull Function0 f) {
Intrinsics.checkParameterIsNotNull(f, "f");
f.invoke();
}
public final void inlineRun(@NotNull Function0 f) {
Intrinsics.checkParameterIsNotNull(f, "f");
f.invoke();
}
public final void main() {
this.run((Function0)null.INSTANCE);
String var2 = "inlineRun";
System.out.print(var2);
}
}

45. Inline
public final class Sample {
public final void run(@NotNull Function0 f) {
Intrinsics.checkParameterIsNotNull(f, "f");
f.invoke();
}
public final void inlineRun(@NotNull Function0 f) {
Intrinsics.checkParameterIsNotNull(f, "f");
f.invoke();
}
public final void main() {
this.run((Function0)null.INSTANCE);
String var2 = "inlineRun";
System.out.print(var2);
}
}

47. • X be Y not error_message
• not
• not
error message
• be 20
not error message “20 ”

48. Validation<User> {
"name"{
be { name.length >= 5 } not "5文字以下"
be { name.length <= 10 } not "10文字以下"
}
"age"{
be { age >= 20 } not error message "20歳以上"
}
}
•

49. fun be(f: T.() -> Boolean) = f
infix fun (T.() -> Boolean).not(???) : ???
be { age >= 20 } not error message "20歳以上"
• error message
•

50. Syntax object
object error
infix fun (T.() -> Boolean).not(syntax: error) = this
infix fun (T.() -> Boolean).message(message: String) {
validations.add(Pair(this, message))
}
be { age >= 20 } not error message "20歳以上"
• object error this
• not message

51. Syntax object
object error
infix fun (T.() -> Boolean).not(syntax: error) = this
infix fun (T.() -> Boolean).message(message: String) {
validations.add(Pair(this, message))
}
be { age >= 20 } not error message “20歳以上"
• object error this
• not message

52. IDE
be { age >= 0 } not error not error not error …
•
• not error
•
•
• not error message

53. IDE
class ErrorMessageSyntax<T>(val validation: T.() -> Boolean)
infix fun (T.() -> Boolean).not(syntax: error) =
ErrorMessageSyntax(this)
infix fun ErrorMessageSyntax<T>.message(message: String) {
validations.add(Pair(this.validation, message))
}
•
•
•

54. IDE
be { age >= 0 } not error
•
•

55. be { age >= 20 } not with callback "20歳以上入力"{
print("debug log")
}
class WithCallbackSyntax<T>(val validation: T.() -> Boolean)
infix fun (T.() -> Boolean).not(syntax: with) =
WithCallbackSyntax(this)
•
• error with
•
• GitHub

56. •
•
•

58. • User Todo
•

60. DSL
• User 5 …
• Todo …
•
• Validations { define<T> }
DSL

61. define
define

62. Validations {
define<User> {
"name"{
be { name.isNotBlank() } not "入力してください"
be { name.length >= 5 } not "5文字以上入力"
be { name.length <= 10 } not "10文字以下で入力"
}
"age"{
be { age >= 0 } not "入力してください"
be { age >= 20 } not "20歳以上で入力"
}
}
define<Todo> {
"body"{
be { body.isNotBlank() } not "入力してください"
}
}
}

63. define
define

64. Validations {
}
object Validations {
val map = mutableMapOf<String, Any>()
operator fun invoke(init: Validations.() -> Unit) {
init()
}
}

65. define Validation<T>
Validations {
define<User> {
}
}
object Validations {
inline fun <reified T>
define(init: ValidationBuilder<T>.() -> Unit) {
val validation = ValidationBuilder<T>().apply(init).build()
val key = (T::class.java).run {
"${`package`.name}.$simpleName"
}
map[key] = validation
}
}

66. Validations {
define<User> {
"name"{
be { name.length >= 5 } not "5文字以上入力"
be { name.length <= 10 } not "10文字以下で入力"
}
"age"{
be { age >= 0 } not "入力してください"
be { age >= 20 } not "20歳以上で入力"
}
}
define<Todo> {
"body"{
be { body.isNotBlank() } not "入力してください"
}
}
}
//{name=[5文字以上入力], age=[20歳以上で入力]}
Validations.validate(User("k",1).validate())
//{body=[入力してください]}
Validations.validate(Todo("").validate())

68. •
•
•
•
•

69. inline fun <reified T> T.validate() =
Validations.validate(this)
•
•

70. Validations {
define<User> {
"name"{
be { name.length >= 5 } not "5文字以上入力"
be { name.length <= 10 } not "10文字以下で入力"
}
"age"{
be { age >= 0 } not "入力してください"
be { age >= 20 } not "20歳以上で入力"
}
}
define<Todo> {
"body"{
be { body.isNotBlank() } not "入力してください"
}
}
}
//{name=[5文字以上入力], age=[20歳以上で入力]}
User("k",1).validate()
//{body=[入力してください]}
Todo("").validate()

71. •
• validate
• define

72. • interface
• interface

73. interface Validable
inline fun <reified T : Validable> T.validate()
= Validations.validate(this)
• Validable
validate
• validate

74. class User(val name: String, val age: Int) : Validable
class Todo(val body: String) : Validable
Validations {
define<User> {
"name"{
be { name.length >= 5 } not "5文字以上入力"
be { name.length <= 10 } not "10文字以下で入力"
}
"age"{
be { age >= 0 } not "入力してください"
be { age >= 20 } not "20歳以上で入力"
}
}
define<Todo> {
"body"{
be { body.isNotBlank() } not "入力してください"
}
}
}
User("k",1).validate()
Todo("").validate()

75. interface Validable<T> {
val key: String
fun validate(): Map<String, List<String>> =
(Validations.get(key) as Validation<T>).validate(this as T)
}
}
inline fun <reified T> Validable<T>.key() =
Validations.key<T>()
class User(val name: String, val age: Int) : Validable<User> {
override val key: String = key()
}
User("k", 3).validate()

76. /
•
•
get,setter

77. (Delegated Properties)
class Delegate : ReadWriteProperty<Hoge, String> {
var value = ""
override fun getValue(thisRef: Hoge, property: KProperty<*>): String {
return "value:" + value
}
override fun setValue(thisRef: Hoge, property: KProperty<*>, value: String) {
this.value = value
}
}
class Hoge {
var x by Delegate()
}
fun main() {
val hoge = Hoge()
hoge.x = "test"
print(hoge.x) // value: test
}

78. (Delegated Properties)
object ValidableDelegate {
class Validable<T>(private val key: String)
: ReadOnlyProperty<Any, Validation<T>> {
override fun getValue(thisRef: Any, property: KProperty<*>)
: Validation<T> {
return Validations.get(key) as Validation<T>
}
}
inline fun <reified T> get() = Validable<T>(Validations.key<T>())
}
class Todo(val body: String) {
private val validation by ValidableDelegate.get<Todo>()
fun validate() = validation.validate(this)
}
Todo("").validate()

79. • inline
• syntax object
• Interface
• interface
• /