DSLs in a Kotlin Way - V2

Presentation about Kotlin machinery for DSL grammars. Updated version for a previous talk.

Oferred at the following events

- The Developers Conference, Kotlin Track (July / 2018)

1. DSLs IN A KOTLIN WAY Ubiratan Soares July / 2018 VERSION 2.0
3. SELECT * FROM accounts WHERE id=12345
4. SELECT * FROM accounts WHERE id=12345 " "
5. String sql = SQLiteQueryBuilder .select("*") .from("accounts") .where("id=12345") .toString(); https://github.com/alexfu/SQLiteQueryBuilder
6. <!DOCTYPE html> <html> <body> <h1>Hey!!"h1> <div>Ho!<span>Lets go!!"span> !"div> !"body> !"html>
7. val tree = createHTMLDocument().html { body { h1 { +"Hey" } div { +"Ho!" span { +"Lets go!" } } } } https://github.com/Kotlin/kotlinx.html
11. Disclaimer : Strategic jump
12. Type Aliases Sealed Classes Extension Functions Extension Properties ETC
13. VERSION 1.0
14. INFIX NOTATION
15. class Extractor { fun firstLetter(target: String) = target[0].toString() } val k = Extractor().firstLetter("Kotlin")
16. class Extractor { infix fun firstLetter(target: String) = target[0].toString() } val k = Extractor() firstLetter "Kotlin"
17. object extract { infix fun firstLetterOf(target: String) = target[0].toString() }
18. object extract { infix fun firstLetterOf(target: String) = target[0].toString() } val first = extract firstLetterOf "Awesome"
20. object acronymn { infix fun from(target: String) = Chainer( initials = mutableListOf(), seed = target ) }
21. object acronymn { infix fun from(target: String) = Chainer( initials = mutableListOf(), seed = target ) }
22. class Chainer( private val initials: MutableList<String>, seed: String) { init { initials += seed.first().toString() }
23. class Chainer(…) { init { initials += seed.first().toString() } infix fun and(another: String) = Chainer(initials, another)
24. class Chainer(…) { init { initials += seed.first().toString() } infix fun and(another: String) = Chainer(initials, another)
25. sealed class Joiner object noPunctuaction : Joiner() object dots : Joiner()
26. class Chainer(…) { infix fun joinedWith(option: Joiner) = initials.reduce { previous, letter !" val next = when (option) { is noPunctuaction !" letter is dots !" "$letter." } "$previous$next" }
27. class Chainer(…) { infix fun joinedWith(option: Joiner) = initials.reduce { previous, letter !" val next = when (option) { is noPunctuaction !" letter is dots !" "$letter." } "$previous$next" }
28. class Chainer(…) { infix fun joinedWith(option: Joiner) = initials.reduce { previous, letter !" val next = when (option) { is noPunctuaction !" letter is dots !" "$letter." } "$previous$next" }
29. class Chainer(…) { infix fun joinedWith(option: Joiner) = initials.reduce { previous, letter !" val next = when (option) { is noPunctuaction !" letter is dots !" "$letter." } "$previous$next" }
30. val dsl = acronymn from "Domain" and "Specific" and "Language" joinedWith noPunctuaction //DSL
31. val dsl = acronymn from "Domain" and "Specific" and "Language" joinedWith dots //D.S.L
32. OPERATOR OVERLOADS
33. val items = mutableListOf(1, 2, 3) items += 4
34. val items = mutableListOf(1, 2, 3) items += 4 /#$ * Adds the specified [element] to this mutable collection. %& @kotlin.internal.InlineOnly public inline operator fun <T> MutableCollection<in T>.plusAssign(element: T) { this.add(element) }
35. typealias IntPair = Pair<Int, Int> val calendar by lazy { Calendar.getInstance() }
36. operator fun Date.plus(args: IntPair): Date { calendar.time = this calendar.add(args.first, args.second) return calendar.time } operator fun Date.minus(args: IntPair): Date { calendar.time = this calendar.add(args.first, -args.second) return calendar.time }
37. operator fun Date.plus(args: IntPair): Date { calendar.time = this calendar.add(args.first, args.second) return calendar.time } operator fun Date.minus(args: IntPair): Date { calendar.time = this calendar.add(args.first, -args.second) return calendar.time }
38. fun Int.days() = Calendar.DAY_OF_YEAR to this fun Int.months() = Calendar.MONTH to this val atPast = Date() - 2.months() val atFuture = Date() + 15.days()
39. val Int.days: IntPair get() = Calendar.DAY_OF_YEAR to this val Int.months: IntPair get() = Calendar.MONTH to this
40. val past = Date() - 2.months val future = Date() + 15.days val Int.days: IntPair get() = Calendar.DAY_OF_YEAR to this val Int.months: IntPair get() = Calendar.MONTH to this
41. A The problem like with spannables on Android
42. val toSpan = SpannableStringBuilder() val start = toSpan.length toSpan.append("First Part") toSpan.setSpan( UnderlineSpan(), start, toSpan.length, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE ) toSpan.setSpan( StyleSpan(android.graphics.Typeface.BOLD), start, toSpan.length, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE ) toSpan.append("not bold or underlined")
43. operator fun SpannableString.plus(s: String) = SpannableString(TextUtils.concat(this, s)) operator fun SpannableString.plus(s: SpannableString) = SpannableString(TextUtils.concat(this, s))
44. fun span(given: CharSequence, span: Any): SpannableString { val spannable = if (given is String) SpannableString(given) else given as? SpannableString ?: throw CannotBeSpanned return spannable.apply { setSpan(span, 0, length, SPAN_EXCLUSIVE_EXCLUSIVE) } } object CannotBeSpanned : IllegalArgumentException( "Cannot apply span. Should be String or SpannableString" )
45. // Add more hooks to same span() function fun italic(given: CharSequence) = span(given, StyleSpan(Typeface.ITALIC)) fun underline(given: CharSequence) = span(given, UnderlineSpan()) fun bold(given: CharSequence) = span(given, StyleSpan(Typeface.BOLD))
46. val spanned = "normal" + bold("bold") + italic("italic") label.setText(spanned)
47. LAMBDAS + RECEIVERS
48. fun x(lambda: () !" Unit) { lambda() } fun y(lambda: () !" Int) = lambda() val x: () !" Int = { TODO() } val result = x()
49. val add = fun(a: Int, b: Int) = a + b fun calculate(func: (Int, Int) !" Int) { func.invoke(2,2) } // Trailling Notation calculate { a, b !" a + b } // Normal notation calculate(add)
50. class Receiver(val data: Int) // Kotlin allows us to add an extension function // literal to a type. Such lambda acquires the // properties of non-static method in the context val addOne: Receiver.() !" Int = { data + 1 } val two = addOne(Receiver(1)) val twoAgain = Receiver(1).addOne()
51. fun receive(block: Receiver.() !" Unit) { val r = Receiver(data = 1) block(r) // r.block() is exactly the same } receive { println(data) // 1 }
53. https://graphql.org/swapi-graphql/
54. val starWars = query { allFilms { film { title director } } } println(starWars) > query { allFilms { film { title director } } }
55. val starWars = query { '( TODO }
56. val starWars = query { '( TODO } fun query(): String { return "query { ${ '( Something here } }" }
57. val starWars = query { '( TODO } fun query(setup: AllFilmsBlock.() !" String) = "query { ${setup(AllFilmsBlock())} }"
58. val starWars = query { '( TODO } fun query(setup: AllFilmsBlock.() !" String) = "query { ${setup(AllFilmsBlock())} }"
59. val starWars = query { '( TODO } fun query(setup: AllFilmsBlock.() !" String) = "query { ${setup(AllFilmsBlock())} }"
60. fun query(setup: AllFilmsBlock.() !" String) = "query { ${setup(AllFilmsBlock())} }" val starWars = query { allFilms { // TODO } } class AllFilmsBlock { fun allFilms(setup: FilmBlock.() !" String) = "allFilms { ${setup(FilmBlock())} }" }
61. fun query(setup: AllFilmsBlock.() !" String) = "query { ${setup(AllFilmsBlock())} }" val starWars = query { allFilms { // TODO } } class AllFilmsBlock { fun allFilms(setup: FilmBlock.() !" String) = "allFilms { ${setup(FilmBlock())} }" }
62. val starWars = query { allFilms { film { // TODO } } }
63. val starWars = query { allFilms { film { } } } class FilmBlock { fun film(setup: FilmFields.() !" String) = with(FilmFields()) { setup() "film { ${fields()} }" } }
64. val starWars = query { allFilms { film { } } } class FilmBlock { fun film(setup: FilmFields.() !" String) = with(FilmFields()) { setup() "film { ${fields()} }" } }
65. val starWars = query { allFilms { film { } } } class FilmBlock { fun film(setup: FilmFields.() !" String) = with(FilmFields()) { setup() "film { ${fields()} }" } }
66. class FilmFiels { private val picked = mutableListOf<String>() fun fields() = TODO() val title: String get() { picked.add(TITLE) return TITLE } }
67. class FilmFields { val title: String get() { … } val director: String get() { … } private companion object { const val TITLE = "title" const val DIRECTOR = "director" } }
68. class FilmFields { fun fields() = picked.distinct().joinToString(separator = " ") val title: String get() { … } val director: String get() { … } private companion object { … } }
69. class FilmFields { fun fields() = picked.distinct().joinToString(separator = " ") val title: String get() { … } val director: String get() { … } private companion object { … } }
70. val starWars = query { allFilms { film { title director } } } println(starWars)
72. // Plain old mockWebServer val server = MockWebServer() val response = MockResponse().apply { setResponseCode(503) setBody("Ops!") } server.enqueue(response) server.start()
73. class MockResponseBuilder( '( Aliases var code: Int = 0, var response: String? = null) { fun mockResponse() = MockResponse().apply { setResponseCode(code) setBody(response) } }
74. class QueueBuilder { val mocks = mutableListOf<MockResponse>() fun enqueueMock(setup: MockResponseBuilder.() !" Unit) { val builder = MockResponseBuilder() builder.setup() mocks.add(builder.mockResponse()) } }
75. typealias BuildMock = MockResponseBuilder.() !" Unit class QueueBuilder { val mocks = mutableListOf<MockResponse>() fun enqueueMock(setup: BuildMock) = MockResponseBuilder().run { setup() mocks.add(mockResponse()) } }
76. typealias BuildMock = MockResponseBuilder.() !" Unit class QueueBuilder { val mocks = mutableListOf<MockResponse>() fun enqueueMock(setup: BuildMock) = MockResponseBuilder().run { setup() mocks.add(mockResponse()) } }
77. typealias BuildQueue = QueueBuilder.() !" Unit fun newServer(setup: BuildQueue): MockWebServer = with(MockWebServer()) { '( ???? return this }
78. typealias BuildQueue = QueueBuilder.() !" Unit fun newServer(setup: BuildQueue): MockWebServer = with(MockWebServer()) { QueueBuilder().run { setup() mocks.forEach { enqueue(it) } } return this }
79. typealias BuildQueue = QueueBuilder.() !" Unit fun newServer(setup: BuildQueue): MockWebServer = with(MockWebServer()) { QueueBuilder().run { setup() mocks.forEach { enqueue(it) } } return this }
80. // DSL based val server = newServer { enqueueMock { code = 200 response = "OK" } } server.start() // Plain old mockWebServer val server = MockWebServer() val response = MockResponse().apply { setResponseCode(503) setBody("Ops!") } server.enqueue(response) server.start()
82. FINAL
 REMARKS
83. CONCLUSIONS • DSLs are fun (with no pun) • DSL-building offer great insights over Kotlin features! • DSLs should work to improve an existing domain, not replace it • Design your own DSLs for fun and profit !
84. https://speakerdeck.com/ubiratansoares
85. UBIRATAN SOARES Computer Scientist by ICMC/USP Software Engineer, curious guy Google Expert for Android and Kotlin Teacher, speaker, etc, etc
86. THANK YOU @ubiratanfsoares ubiratansoares.github.io https://br.linkedin.com/in/ubiratanfsoares