Kotlin DSLs

Talk held at Android Makers, Paris (https://androidmakers.fr/)

Transcript

1. KOTLIN DSLs Wolfram Rittmeyer
2. 2 What are DSLs
3. 3 DSLs • Easily understandable • Make the intention obvious • Are specific to a problem
4. 4 DSLs • External DSLs – Use any language to implement it • Internal DSLs – Uses host language – Uses normal language constructs – Can use language constructs within DSL
5. 5 Samples
6. 6 kotlintest should("verify names in map") { //... name should (startWith("test") or endWith("Name")) name shouldBe "testName" ageMap should contain("testName") }
7. 7 Koin val appModule = applicationContext { val db = SomeDatabase.getInstance(applicationContext) bean { db.entryDao } bean { SomeApi.create(BuildConfig.DEBUG) } bean("MainScheduler") { AndroidSchedulers.mainThread() as Scheduler } factory { AndroidNotifBuilder(applicationContext) as NotificationBuilder } }
8. 8 Anko constraintLayout { val title = textView { id = R.id.txtTitle textAppearance = R.style.TextAppearance_AppCompat_Large textColor = R.color.titleText } applyConstraintSet { title { connect( TOP to TOP of PARENT_ID margin dip(16), START to START of PARENT_ID margin dip(16) ) } } }
9. 9 How is it done?
10. 10 mockK view = mockk<CarDiscoveryView>(relaxed = true) // ... every { view.setRemoteVehicles(vehicles = capture(params)) } just runs
11. 11 mockK just runs
12. 12 mockK
13. 13 mockK /** * Part of DSL. Answer placeholder for Unit returning functions. */ infix fun MockKStubScope<Unit>.just(runs: Runs) = answers(ConstantAnswer(Unit))
14. 14 mockK /** * Part of DSL. Answer placeholder for Unit returning functions.
15. 15 mockK just(runs)
16. 16 mockK just runs
17. 17 Concepts covered so far • Infix calls
18. 18 mockK view = mockk<CarDiscoveryView>(relaxed = true) // ... every { view.setRemoteVehicles(vehicles = capture(params)) } just runs
19. 19 mockK just runs
20. 20 mockK runs
21. 21 mockK /** * Part of DSL. Object to represent phrase "just Runs" */ object Runs typealias runs = Runs
22. 22 Concepts covered so far • Infix calls • Empty object • Type aliases
23. 23 kotlintest class CalenderListScreen : ShouldSpec() { init { should("display channelMap in list") { // ... } } }
24. 24 kotlintest
25. 25 kotlintest fun should(name: String, test: () -> Unit): TestCase { val testCase = TestCase( suite = current, name = "should $name", test = test, config = defaultTestCaseConfig) current.addTestCase(testCase) return testCase }
26. 26 kotlintest
27. 27 kotlintest
28. 28 kotlintest
29. 29 Concepts covered so far • Infix calls • Empty object • Type aliases • Trailing lambdas
30. 30 kotlintest class CalenderListScreen : ShouldSpec() { init { should("display channelMap in list") { // ... } } }
31. 31 kotlintest class CalenderListScreen : StringSpec() { init { "should display channelMap in list" { // ... } } }
32. 32 kotlintest
33. 33 kotlintest operator fun String.invoke(test: () -> Unit): TestCase { val tc = TestCase(suite = rootTestSuite, name = this, test = test, config = defaultTestCaseConfig) rootTestSuite.addTestCase(tc) return tc }
34. 34 kotlintest
35. 35 Concepts covered so far • Infix calls • Empty object • Type aliases • Trailing lambdas • Extension functions • Conventions
36. 36 kotlinx.html val html = buildString { appendHTML().html { body { div { +"Some text inside the div" } } } }
37. 37 kotlinx.html +"Some text inside the div"
38. 38 kotlinx.html @kotlinx.html.HtmlTagMarker public interface Tag { // ... public open operator fun kotlin.String.unaryPlus(): kotlin.Unit { /* ... */ } // ... }
39. 39 kotlinx.html
40. 40 Concepts covered so far • Infix calls • Empty object • Type aliases • Trailing lambdas • Conventions • Extension functions • Operator overloading
41. 41 Koin val appModule = applicationContext { val db = SomeDatabase.getInstance(applicationContext) bean { db.entryDao } bean { SomeApi.create(BuildConfig.DEBUG) } bean("MainScheduler") { AndroidSchedulers.mainThread() as Scheduler } factory { AndroidNotifBuilder(applicationContext) as NotificationBuilder } }
42. 42 Koin
43. 43 Koin fun applicationContext(init: Context.() -> Unit): Module = { Context(Scope.ROOT, StandAloneContext.koinContext as KoinContext).apply(init) }
44. 44 Koin
45. 45 Koin fun applicationContext(init: Context.() -> Unit): Module = { Context(Scope.ROOT, StandAloneContext.koinContext as KoinContext).apply(init) }
46. 46 Koin fun applicationContext(init: Context.() -> Unit): Module = { val ctx = Context(Scope.ROOT, StandAloneContext.koinContext as KoinContext) ctx.init() }
47. 47 Lambda vs. Lambda with receivers "heyho".also { str -> println(str) }
48. 48 Lambda vs. Lambda with receivers "heyho".also { println(it) }
49. 49 Lambda vs. Lambda with receivers "heyho".also { println(it) } "heyho".apply { println(this) }
50. 50 Lambda vs. Lambda with receivers // slightly simplified public inline fun <T> T.also(block: (T) -> Unit): T { block(this) return this } // slightly simplified public inline fun <T> T.apply(block: T.() -> Unit): T { block() return this }
51. 51 Lambda vs. Lambda with receivers
52. 52 Lambda with receivers in DSLs
53. 53 Lambda with receivers in DSLs fun applicationContext(init: Context.() -> Unit): Module = { val ctx = Context(Scope.ROOT, StandAloneContext.koinContext as KoinContext) ctx.init() }
54. 54 Concepts covered so far • Infix calls • Empty object • Type aliases • Trailing lambdas • Conventions • Extension functions • Operator overloading • Lambda with Receivers
55. 55 Anko constraintLayout { val title = textView { id = R.id.txtTitle textAppearance = R.style.TextAppearance_AppCompat_Large textColor = R.color.titleText } applyConstraintSet { title { connect( TOP to TOP of PARENT_ID margin dip(16), START to START of PARENT_ID margin dip(16) ) } } }
56. 56 Anko
57. 57 Anko inline fun ViewManager.textView( init: (@AnkoViewDslMarker android.widget.TextView).() -> Unit) : android.widget.TextView {
58. 58 Anko
59. 59 Anko @DslMarker @Target(AnnotationTarget.TYPE) annotation class AnkoViewDslMarker
60. 60 Concepts • Infix calls • Empty object • Type aliases • Trailing lambdas • Conventions • Extension functions • Operator overloading • Lambda with Receivers • Scope limiting
61. 61 Summary
62. 62 Concepts covered so far • Infix calls • Empty object • Type aliases • Trailing lambdas • Conventions • Extension functions • Operator overloading • Lambda with Receivers • Scope limiting
63. 63 Designing DSLs • Consider deviating from naming conventions • As per usual: Don’t go overboard • An interesting discussion of approaches: https:/ /github.com/zsmb13/VillageDSL
64. 64 Libs
65. 65 General libs • DI / Service Locating: – Koin – Kodein • Testing – MockK – Spek – kotlintest
66. 66 Android specific libs • Anko • Konduit
67. 67 Libs • Spring Router Config • Spring Bean Config • Gradle Kotlin DSL • kotlinx.HTML • Exposed
68. Q&A www.wolfram-rittmeyer.de twitter.com/RittmeyerW www.grokkingandroid.com