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Beyond Kotlin Advanced features for API makers

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Work @ ekito Mobile & Cloud Kotlin Lover @arnogiu Arnaud GIULIANI medium.com/@giuliani.arnaud/ ekito.fr/people #DevFestToulouse

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Statically typed programming language for modern multiplatform applications

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Kotlin on Android, now official

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h5ps:/ /spring.io/blog/2017/01/04/introducing-kotlin-support-in-spring- framework-5-0 h5p:/ /www.javamagazine.mozaicreader.com/ #&pageSet=5&page=0&contentItem=0 (March/ April 2017) h5ps:/ /www.thoughtworks.com/radar/languages-and-frameworks/kotlin

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h5ps:/ /zeroturnaround.com/rebellabs/developer-producNvity-report-2017-why-do-you-use-java-tools-you-use/

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Many well-known companies are using Kotlin: Pinterest, Coursera, NeUlix, Uber, Square, Trello, Basecamp, amongst others well-known banks (such as Goldman Sachs, Wells Fargo, J.P. Morgan, Deutsche Bank, UBS, HSBC, BNP Paribas, Société Générale)

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KOTLIN is not just a syntactic sugar It’s all about writing SAFER & BETTER APPS !

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val / var Null safety Class / Object Lambda Functions Data Class Properties & delegates Default Values Named Parameters Extension Functions InterOp Not today!

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Let’s take a concrete context

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// A Bean Definition data class BeanDefinition(val name: String, val clazz: KClass<*>) like dependency injection An advanced API development use case Let’s take

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Before, we need some APIs ⚒

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Writing Lambda APIs

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// A Bean definition val beanDef: BeanDefinition? // let beanDef?.let { println("bean name is '${it.name}'") } // let & assign value val complexName: String? = beanDef?.let { "name : ${it.name} & class ${it.clazz}" } Safely executing with let // A Bean definition val beanDef: BeanDefinition? // let beanDef?.let { println("bean name is '${it.name}'") }

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// takeIf (validate predicate) val bean = beanDef?.takeIf { it.name.isNotEmpty() } val bean = beanDef?.takeUnless { it.name.isNullOrEmpty() } // A Bean definition val beanDef: BeanDefinition? = ... // Guard like expression val bean: BeanDefinition = beanDef?.takeIf { it.name.isNotEmpty() } ?: error("bean name is empty") // Guard like expression val bean: BeanDefinition = beanDef?.takeIf { it.name.isNotEmpty() } ?: error("bean name is empty") val bean: BeanDefinition = beanDef?.takeIf { it.name.isNotEmpty() } ?: return // takeIf (validate predicate) val bean = beanDef?.takeIf { it.name.isNotEmpty() } val bean = beanDef?.takeUnless { it.name.isNullOrEmpty() } takeIf & takeUnless // A Bean definition val beanDef: BeanDefinition? = ...

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let ~ run -> return last value also ~ apply -> return itself with() -> function & return last value it let ~ run -> return last value also ~ apply -> return itself with() -> function & return last value this

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Encapsulate behavior for a target object

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Lambda function Receiver Type fun T.function( (T) -> R) fun T.function( T.() -> R) Writing encapsulation 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.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.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.apply(block: T.() -> Unit): T { block(); return this } public inline fun T.also(block: (T) -> Unit): T { block(this); return this }

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SAM Conversion public class JavaBeanDefinition { String name; Class clazz; public JavaBeanDefinition(String name, Class clazz) {...} public void postInit(JavaInitializingBean initBean){ // Register post init } } public interface JavaInitializingBean { void onInitDone(); } val clazz = MyService::class.java val javaBean = JavaBeanDefinition(clazz.simpleName,clazz) public class JavaBeanDefinition { String name; Class clazz; public JavaBeanDefinition(String name, Class clazz) {...} public void postInit(JavaInitializingBean initBean){ // Register post init } } public interface JavaInitializingBean { void onInitDone(); } val clazz = MyService::class.java val javaBean = JavaBeanDefinition(clazz.simpleName,clazz) javaBean.postInit { println("bean has been defined ! ") } JAVA JAVA

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The functional way // A Bean definition with post init data class BeanDefinition(val name: String, val clazz: KClass<*>) { fun postInit(initializingBean: InitializingBean) { // register post init ... } } // A Bean definition with post init data class BeanDefinition(val name: String, val clazz: KClass<*>) { fun postInit(initializingBean: () -> Unit) { // register post init ... } } val clazz = MyService::class val bean = BeanDefinition(clazz.java.simpleName, clazz) val clazz = MyService::class val bean = BeanDefinition(clazz.java.simpleName, clazz) bean.postInit { println("bean has been defined ! ") }

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Types

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Types Hierarchy

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Types Hierarchy (again) ? ?

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Dealing with generics sealed class BeanDefinition(val name : String, val clazz : KClass<*>) class Singleton(n : String, c : KClass<*>) : BeanDefinition(n,c) class Factory(n : String, c : KClass<*>) : BeanDefinition(n,c) fun registerBean(def: T) { //... } // Limit with Bounds fun registerBean(def: T) { //... }

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Dealing with generics sealed class BeanDefinition(val name : String, val clazz : KClass<*>) class Singleton(n : String, c : KClass<*>) : BeanDefinition(n,c) class Factory(n : String, c : KClass<*>) : BeanDefinition(n,c) fun registerBean(def: T) { //... } class BeanProvider { } // Limit with Bounds fun registerBean(def: T) { //... } // Limit with Bounds fun registerBean(def: T) { //... } sealed class BeanDefinition(val name : String, val clazz : KClass<*>) class Singleton(n : String, c : KClass<*>) : BeanDefinition(n,c) class Factory(n : String, c : KClass<*>) : BeanDefinition(n,c)

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Reified Types fun declareBean(name :String, clazz : KClass<*>){ val bean = BeanDefinition(name,clazz) }

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Reified Types fun declareBean(name :String, clazz : KClass<*>){ val bean = BeanDefinition(name,clazz) } fun declareBean(name :String, clazz : T){ val bean = BeanDefinition(name,???) } fun declareBean(name :String, clazz : T){ // Capture Type parameter class val clazz = T::class val bean = BeanDefinition(name,clazz) }

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Reified Types fun declareBean(name :String, clazz : KClass<*>){ val bean = BeanDefinition(name,clazz) } fun declareBean(name :String, clazz : T){ val bean = BeanDefinition(name,???) } fun declareBean(name :String, clazz : T){ // Capture Type parameter class val clazz = T::class val bean = BeanDefinition(name,clazz) } inline fun declareBean(name :String, clazz : T){ // Capture Type parameter class val clazz = T::class val bean = BeanDefinition(name,clazz) }

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Reified Types fun declareBean(name :String, clazz : KClass<*>){ val bean = BeanDefinition(name,clazz) } fun declareBean(name :String, clazz : T){ val bean = BeanDefinition(name,???) } fun declareBean(name :String, clazz : T){ // Capture Type parameter class val clazz = T::class val bean = BeanDefinition(name,clazz) } inline fun declareBean(name :String, clazz : T){ // Capture Type parameter class val clazz = T::class val bean = BeanDefinition(name,clazz) } inline fun declareBean(){ // Capture Type parameter class val clazz = T::class val name = clazz.simpleName ?: "" val bean = BeanDefinition(name,clazz) }

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Reified Types fun declareBean(name :String, clazz : KClass<*>){ val bean = BeanDefinition(name,clazz) } fun declareBean(name :String, clazz : T){ val bean = BeanDefinition(name,???) } fun declareBean(name :String, clazz : T){ // Capture Type parameter class val clazz = T::class val bean = BeanDefinition(name,clazz) } inline fun declareBean(name :String, clazz : T){ // Capture Type parameter class val clazz = T::class val bean = BeanDefinition(name,clazz) } inline fun declareBean(){ // Capture Type parameter class val clazz = T::class val name = clazz.simpleName ?: "" val bean = BeanDefinition(name,clazz) } inline fun declareBean(){ // Capture Type parameter class val clazz = T::class val name = clazz.simpleName ?: "" val bean = BeanDefinition(name,clazz) } declareBean()

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Type Aliases typealias BeanList = List typealias BeanList = List val list : BeanList = listOf()

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Type Aliases typealias BeanList = List typealias BeanList = List val list : BeanList = listOf() typealias BeanValidator = (BeanDefinition) -> Boolean typealias BeanList = List val list : BeanList = listOf() typealias BeanValidator = (BeanDefinition) -> Boolean val bv : BeanValidator = { def -> def.name.isNotEmpty()}

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Type Aliases typealias BeanList = List typealias BeanList = List val list : BeanList = listOf() typealias BeanValidator = (BeanDefinition) -> Boolean typealias BeanList = List val list : BeanList = listOf() typealias BeanValidator = (BeanDefinition) -> Boolean val bv : BeanValidator = { def -> def.name.isNotEmpty()} typealias BeanValidator = (BeanDefinition) -> Boolean val bv : BeanValidator = { def -> def.name.isNotEmpty()} // A Bean definition with post init data class BeanDefinition(val name: String, val clazz: KClass<*>) { fun validate(validator: BeanValidator) : Boolean = validator(this) } // A Bean definition with post init data class BeanDefinition(val name: String, val clazz: KClass<*>) { fun validate(validator: BeanValidator) : Boolean = validator(this) }

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Type Aliases typealias BeanList = List typealias BeanList = List val list : BeanList = listOf() typealias BeanValidator = (BeanDefinition) -> Boolean typealias BeanList = List val list : BeanList = listOf() typealias BeanValidator = (BeanDefinition) -> Boolean val bv : BeanValidator = { def -> def.name.isNotEmpty()} typealias BeanValidator = (BeanDefinition) -> Boolean val bv : BeanValidator = { def -> def.name.isNotEmpty()} // A Bean definition with post init data class BeanDefinition(val name: String, val clazz: KClass<*>) { fun validate(validator: BeanValidator) : Boolean = validator(this) } // A Bean definition with post init data class BeanDefinition(val name: String, val clazz: KClass<*>) { fun validate(validator: BeanValidator) : Boolean = validator(this) } // A Bean definition with post init data class BeanDefinition(val name: String, val clazz: KClass<*>) { fun validate(validator: BeanValidator) : Boolean = validator(this) }

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Ready to write our API

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Making clean syntax StringUtil.capitalize(s) s.capitalize() Extension FuncNon 1.to("one") 1 to "one" Infix call set.add(2) set += 2 Operator overloading map.get("key") map["key"] Get method convenNon StringUtil.capitalize(s) 1.to("one") set.add(2) map.get("key")

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file.use({f -> f.read()}) file.use {f -> f.read()} Lambda outside parenthesis sb.append("yes") sb.append("no") with (sb){ append("yes") append("no") } Lambda with receiver file.use({f -> f.read()}) sb.append("yes") sb.append("no") Making clean syntax

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API or DSL?

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DSL - a small set of features - focus on a particular task declarative API - a set of functions and procedures - for creation of applications imperative => internal DSL

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Dependency injection DSL

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provide { MyService() } Builder function Type reference () -> MyService MyService::class fun provide( definition : () -> T )

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provide { MyServiceA() } declareContext { } provide { MyServiceB( ? ) } provide { MyServiceC( ? , ?) } data class MyServiceA() data class MyServiceB(val a : MyServiceA) data class MyServiceC(val a : MyServiceA, val b : MyServiceB) provide { MyServiceC(get(),get()) } provide { MyServiceB(get()) }

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fun provide(definition: () -> T) { } data class BeanDefinition(val name: String, val clazz: KClass<*>)

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fun provide(definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName val bean = BeanDefinition(name,clazz) } data class BeanDefinition(val name: String, val clazz: KClass<*>)

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inline fun provide(definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName val bean = BeanDefinition(definition, name, clazz) } data class BeanDefinition(val name: String, val clazz: KClass<*>)

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inline fun provide(definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName val bean = BeanDefinition(definition, name, clazz) } data class BeanDefinition(val definition: () -> T, val name : String, val clazz : KClass<*>)

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inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName val bean = BeanDefinition(definition, name, clazz) } data class BeanDefinition(val definition: () -> T, val name : String, val clazz : KClass<*>)

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class Context { inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName val bean = BeanDefinition(definition, name, clazz) } } data class BeanDefinition(val definition: () -> T, val name : String, val clazz : KClass<*>)

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class Context { var definitions = listOf>() inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName definitions += BeanDefinition(definition, name, clazz) } } data class BeanDefinition(val definition: () -> T, val name : String, val clazz : KClass<*>)

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class Context { var definitions = listOf>() inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName definitions += BeanDefinition(definition, name, clazz) } } data class BeanDefinition(val definition: () -> T, val name : String, val clazz : KClass<*>) fun declareContext(init: Context.() -> Unit) = Context().apply(init)

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class Context { var definitions = listOf>() inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName definitions += BeanDefinition(definition, name, clazz) } } data class BeanDefinition(val definition: () -> T, val name : String, val clazz : KClass<*>) fun declareContext(init: Context.() -> Unit) = Context().apply(init)

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class Context { var definitions = listOf>() inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName definitions += BeanDefinition(definition, name, clazz) } } data class BeanDefinition(val definition: () -> T, val name : String, val clazz : KClass<*>) fun declareContext(init: Context.() -> Unit) = Context().apply(init)

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declareContext { } provide { MyServiceB( ? ) } provide { MyServiceC( ? , ?) } data class MyServiceA() data class MyServiceB(val a : MyServiceA) data class MyServiceC(val a : MyServiceA, val b : MyServiceB) provide { MyServiceA() } provide { MyServiceC(get(),get()) } provide { MyServiceB(get()) }

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class Context { var definitions = listOf>() inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName definitions += BeanDefinition(definition, name, clazz) } } data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) fun declareContext(init: Context.() -> Unit) = Context().apply(init)

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) fun declareContext(init: Context.() -> Unit) = Context().apply(init) class Context { var definitions = listOf>() inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName definitions += BeanDefinition(definition, name, clazz) } } var instances = HashMap,Any>()

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) fun declareContext(init: Context.() -> Unit) = Context().apply(init) class Context { var definitions = listOf>() inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName definitions += BeanDefinition(definition, name, clazz) } fun get() : T{} } var instances = HashMap,Any>()

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) fun declareContext(init: Context.() -> Unit) = Context().apply(init) class Context { var definitions = listOf>() inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName definitions += BeanDefinition(definition, name, clazz) } fun get() : T = instances[T::class] } var instances = HashMap,Any>()

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) fun declareContext(init: Context.() -> Unit) = Context().apply(init) class Context { var definitions = listOf>() inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName definitions += BeanDefinition(definition, name, clazz) } inline fun get() : T = instances[T::class] } var instances = HashMap,Any>()

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) fun declareContext(init: Context.() -> Unit) = Context().apply(init) class Context { var definitions = listOf>() inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName definitions += BeanDefinition(definition, name, clazz) } inline fun get() : T = instances[T::class] as T } var instances = HashMap,Any>()

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provide { MyServiceA() } declareContext { } provide { MyServiceB( ? ) } provide { MyServiceC( ? , ?) } data class MyServiceA() : MyServiceA data class MyServiceB(val a : MyServiceA) data class MyServiceC(val a : MyServiceA, val b : MyServiceB) provide { MyServiceC(get(),get()) } provide { MyServiceB(get()) }

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provide { MyServiceA() } declareContext { } provide { MyServiceB( ? ) } provide { MyServiceC( ? , ?) } data class MyServiceA() : MyServiceA data class MyServiceB(val a : MyServiceA) data class MyServiceC(val a : MyServiceA, val b : MyServiceB) provide { MyServiceC(get(),get()) } provide { MyServiceB(get()) } Lazy evaluated by nature!

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provide { MyServiceA() } declareContext { } data class MyServiceA() : MyServiceA data class MyServiceB(val a : MyServiceA) data class MyServiceC(val a : MyServiceA, val b : MyServiceB) provide { MyServiceC(get(),get()) } provide { MyServiceB(get()) }

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) fun declareContext(init: Context.() -> Unit) = Context().apply(init) class Context { var definitions = listOf>() inline fun provide(noinline definition: () -> T) { val clazz = T::class val name = clazz.java.simpleName definitions += BeanDefinition(definition, name, clazz) } inline fun get() : T = instances[T::class] as T } var instances = HashMap,Any>()

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) fun declareContext(init: Context.() -> Unit) = Context().apply(init) class Context {...} var instances = HashMap,Any>()

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) abstract class Module { abstract fun context() : Context } class Context {...} var instances = HashMap,Any>()

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) abstract class Module { abstract fun context() : Context fun declareContext(init: Context.() -> Unit) = Context().apply(init) } class Context {...} var instances = HashMap,Any>()

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class SimpleModule : Module() { override fun context() = declareContext { provide { ServiceA() } provide { ServiceB(get()) } provide { ServiceC(get(), get()) } } } data class MyServiceA() data class MyServiceB(val a : MyServiceA) data class MyServiceC(val a : MyServiceA, val b : MyServiceB) Entirely declarative

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Dependency resolution API

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) abstract class Module { abstract fun context() : Context fun declareContext(init: Context.() -> Unit) = Context().apply(init) } class Context {...} var instances = HashMap,Any>()

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) class Context {...} abstract class Module { abstract fun context() : Context fun declareContext(init: Context.() -> Unit) = Context().apply(init) } class CoreContext{ var instances = HashMap,Any>() var definitions = listOf>() }

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) class Context {...} abstract class Module(){ lateinit var coreContext: CoreContext abstract fun context() : Context fun declareContext(init: Context.() -> Unit) = Context(coreContext).apply(init) } class CoreContext{ var instances = HashMap,Any>() var definitions = listOf>() }

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) class Context {...} abstract class Module(){ lateinit var coreContext: CoreContext abstract fun context() : Context fun declareContext(init: Context.() -> Unit) = Context(coreContext).apply(init) } class CoreContext{ var instances = HashMap,Any>() var definitions = listOf>() }

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data class BeanDefinition(val definition: () -> T, val name: String, val clazz: KClass<*>) class Context(val coreContext: CoreContext) { ... } abstract class Module(){ lateinit var coreContext: CoreContext abstract fun context() : Context fun declareContext(init: Context.() -> Unit) = Context(coreContext).apply(init) } class CoreContext{ var instances = HashMap,Any>() var definitions = listOf>() }

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class Context(val coreContext: CoreContext) { //... inline fun get() : T = instances[T::class] }

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class Context(val coreContext: CoreContext) { //... inline fun get() : T = coreContext.inject() }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() fun inject(): T {} }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() fun inject(): T { val clazz = T::class } }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() inline fun inject(): T { val clazz = T::class } }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() inline fun inject(): T { val clazz = T::class // found one ? val foundInstance: T? = instances[clazz] as? T } }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() inline fun inject(): T { val clazz = T::class // found one ? val foundInstance: T? = instances[clazz] as? T // create one ? val createdInstance: T? = if (foundInstance == null) { definitions.firstOrNull { it.clazz == clazz }?.let { it.definition.invoke() as? T? } } else null } }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() inline fun inject(): T { val clazz = T::class // found one ? val foundInstance: T? = instances[clazz] as? T // create one ? val createdInstance: T? = if (foundInstance == null) { definitions.firstOrNull { it.clazz == clazz }?.let { it.definition.invoke() as? T? } } else null } }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() inline fun inject(): T { val clazz = T::class // found one ? val foundInstance: T? = instances[clazz] as? T // create one ? val createdInstance: T? = if (foundInstance == null) { definitions.firstOrNull { it.clazz == clazz }?.let { it.definition.invoke() as? T? } } else null } }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() inline fun inject(): T { val clazz = T::class // found one ? val foundInstance: T? = instances[clazz] as? T // create one ? val createdInstance: T? = if (foundInstance == null) { definitions.firstOrNull { it.clazz == clazz }?.let { it.definition.invoke() as? T? } } else null } }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() inline fun inject(): T { val clazz = T::class // found one ? val foundInstance: T? = instances[clazz] as? T // create one ? val createdInstance: T? = if (foundInstance == null) { definitions.firstOrNull { it.clazz == clazz }?.let { it.definition.invoke() as? T? } } else null // Got it val instance: T = (foundInstance ?: createdInstance) ?: error("Bean $clazz not found") } }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() inline fun inject(): T { val clazz = T::class // found one ? val foundInstance: T? = instances[clazz] as? T // create one ? val createdInstance: T? = if (foundInstance == null) { definitions.firstOrNull { it.clazz == clazz }?.let { it.definition.invoke() as? T? } } else null // Got it val instance: T = (foundInstance ?: createdInstance) ?: error("Bean $clazz not found ») // Save it if (createdInstance != null && foundInstance == null) { instances[clazz] = createdInstance as Any } } }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() inline fun inject(): T { val clazz = T::class // found one ? val foundInstance: T? = instances[clazz] as? T // create one ? val createdInstance: T? = if (foundInstance == null) { definitions.firstOrNull { it.clazz == clazz }?.let { it.definition.invoke() as? T? } } else null // Got it val instance: T = (foundInstance ?: createdInstance) ?: error("Bean $clazz not found") // Save it if (createdInstance != null && foundInstance == null) { instances[clazz] = createdInstance as Any } return instance } }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() fun build(module: T) {} inline fun inject(): T {} }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() fun build(module: T) { module.coreContext = this } inline fun inject(): T {} }

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class CoreContext { var instances = HashMap, Any>() var definitions = listOf>() fun build(module: T) { module.coreContext = this definitions += module.context().definitions } inline fun inject(): T {} }

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data class MyServiceA() data class MyServiceB(val a : MyServiceA) data class MyServiceC(val a : MyServiceA, val b : MyServiceB) class SimpleModule : Module() { override fun context() = declareContext { provide { ServiceA() } provide { ServiceB(get()) } provide { ServiceC(get(), get()) } } } Let’s use it

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val ctx = CoreContext() ctx.build(SimpleModule()) data class MyServiceA() data class MyServiceB(val a : MyServiceA) data class MyServiceC(val a : MyServiceA, val b : MyServiceB) class SimpleModule : Module() { override fun context() = declareContext { provide { ServiceA() } provide { ServiceB(get()) } provide { ServiceC(get(), get()) } } }

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val ctx = CoreContext() ctx.build(SimpleModule()) val serviceB = ctx.inject() data class MyServiceA() data class MyServiceB(val a : MyServiceA) data class MyServiceC(val a : MyServiceA, val b : MyServiceB) class SimpleModule : Module() { override fun context() = declareContext { provide { ServiceA() } provide { ServiceB(get()) } provide { ServiceC(get(), get()) } } }

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No code generation No annotation No introspection No proxy

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Reflection -> Kclass, KProperty, KFunction … -> Java => Extra lib And also … Extra Binding Lazy Inject

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No content

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https:/ /github.com/Ekito/koin

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Collections & Concurrency

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Collections

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KEEP immutable collections - « real » immutable collections - avoid java backed collections New in 1.1 - Array-Like instantiation - onEach() - minOf/maxOf - groupingBy() - Map : minus(), getValue() Collections

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Stream API (Kotlin on Java 8+) - toStream() Collection to Sequences (Pure Kotlin or Java 6/7) - asSequence() Lazy Collections

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sequence.map {…} .filter {…} .toList() Intermediate operations terminal operation sequence.map {…} .filter {…} .toList() sequence.map {…} .filter {…} .toList()

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Async Programming

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⚠ Experimental feature ⚠

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kotlinx.coroutines

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Kotlin >= 1.1.4 Gradle: compile ‘org.jetbrains.kotlinx:kotlinx-coroutines-core:0.18’ Remove warnings: kotlin { experimental { coroutines "enable" } }

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Suspend - keyword, mark function as « suspending function » Coroutines - API for computations that can be suspended without blocking a thread - launched with coroutine builder (light-weight threads)

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WELCOME TO THE ASYNC WORLD

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@Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } }

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@Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } }

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@Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } }

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@Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } }

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@Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } }

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@Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } @Test fun test() = runBlocking { val main = measureTimeMillis { val jobs = List(100_000) { launch(CommonPool) { delay(1000L) print(".") } } jobs.forEach { it.join() } } println("\ndone in $main") }

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@Test fun test() = runBlocking { val main = measureTimeMillis { val jobs = List(100_000) { launch(CommonPool) { doSomething() } } jobs.forEach { it.join() } } println("\ndone in $main") } suspend fun doSomething() { delay(1000L) print(".") }

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suspend fun delay(time: Long, unit: TimeUnit = TimeUnit.MILLISECONDS) {…} suspend fun delay(time: Long, unit: TimeUnit = TimeUnit.MILLISECONDS) public fun runBlocking(context: CoroutineContext = EmptyCoroutineContext, block: suspend CoroutineScope.() -> T): T {…}

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Kotlin coroutines ~ 1s Java ForkJoin ~ 15s

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Dispatching jobs

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@Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 }

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@Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 }

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@Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 }

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@Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 }

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@Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 }

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@Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 }

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@Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 }

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@Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 }

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@Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 } @Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 }

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@Test
 fun testWeather() = runBlocking {
 log("starting ...")
 val ws = retrofitWS("https://weather-api.herokuapp.com/")
 try {
 val location = asyncGeocode(ws).await() ?: error("No location :(")
 val weather = asyncWeather(location, ws).await()
 log("got weather : $weather")
 } catch (e: Exception) {
 System.err.println("Error is $e")
 }
 log("finished !")
 }
 
 private fun asyncWeather(location: Location, ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get weather for $location")
 ws.weather(location.lat, location.lng, "EN").execute().body()
 }
 
 private fun asyncGeocode(ws: BlockingWeatherWS): Deferred = async(CommonPool) {
 log("get location")
 ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 }

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Data streaming with channels

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@Test
 fun testWeather() = runBlocking {
 val ws = retrofitWS("https://my-weather-api.herokuapp.com/")
 val time = measureTimeMillis {
 val location = channelLocation(ws)
 val weather = channelWeather(location, ws)
 weather.consumeEach { w ->
 log("got weather : $w")
 }
 location.cancel()
 weather.cancel()
 }
 log("\ndone in $time")
 }
 
 private fun channelWeather(locationChannel: ProducerJob, ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get weather for $locationChannel")
 locationChannel.consumeEach { location ->
 val list = ws.weather(location.lat, location.lng, "EN").execute().body().forecast?.simpleforecast?.forecastday?.take(4).orEmpty()
 list.forEach { send(it) }
 }
 }
 
 private fun channelLocation(ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get location")
 val location = ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 location?.let {
 send(location)
 }
 }

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@Test
 fun testWeather() = runBlocking {
 val ws = retrofitWS("https://my-weather-api.herokuapp.com/")
 val time = measureTimeMillis {
 val location = channelLocation(ws)
 val weather = channelWeather(location, ws)
 weather.consumeEach { w ->
 log("got weather : $w")
 }
 location.cancel()
 weather.cancel()
 }
 log("\ndone in $time")
 }
 
 private fun channelWeather(locationChannel: ProducerJob, ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get weather for $locationChannel")
 locationChannel.consumeEach { location ->
 val list = ws.weather(location.lat, location.lng, "EN").execute().body().forecast?.simpleforecast?.forecastday?.take(4).orEmpty()
 list.forEach { send(it) }
 }
 }
 
 private fun channelLocation(ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get location")
 val location = ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 location?.let {
 send(location)
 }
 }

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@Test
 fun testWeather() = runBlocking {
 val ws = retrofitWS("https://my-weather-api.herokuapp.com/")
 val time = measureTimeMillis {
 val location = channelLocation(ws)
 val weather = channelWeather(location, ws)
 weather.consumeEach { w ->
 log("got weather : $w")
 }
 location.cancel()
 weather.cancel()
 }
 log("\ndone in $time")
 }
 
 private fun channelWeather(locationChannel: ProducerJob, ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get weather for $locationChannel")
 locationChannel.consumeEach { location ->
 val list = ws.weather(location.lat, location.lng, "EN").execute().body().forecast?.simpleforecast?.forecastday?.take(4).orEmpty()
 list.forEach { send(it) }
 }
 }
 
 private fun channelLocation(ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get location")
 val location = ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 location?.let {
 send(location)
 }
 }

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@Test
 fun testWeather() = runBlocking {
 val ws = retrofitWS("https://my-weather-api.herokuapp.com/")
 val time = measureTimeMillis {
 val location = channelLocation(ws)
 val weather = channelWeather(location, ws)
 weather.consumeEach { w ->
 log("got weather : $w")
 }
 location.cancel()
 weather.cancel()
 }
 log("\ndone in $time")
 }
 
 private fun channelWeather(locationChannel: ProducerJob, ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get weather for $locationChannel")
 locationChannel.consumeEach { location ->
 val list = ws.weather(location.lat, location.lng, "EN").execute().body().forecast?.simpleforecast?.forecastday?.take(4).orEmpty()
 list.forEach { send(it) }
 }
 }
 
 private fun channelLocation(ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get location")
 val location = ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 location?.let {
 send(location)
 }
 }

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@Test
 fun testWeather() = runBlocking {
 val ws = retrofitWS("https://my-weather-api.herokuapp.com/")
 val time = measureTimeMillis {
 val location = channelLocation(ws)
 val weather = channelWeather(location, ws)
 weather.consumeEach { w ->
 log("got weather : $w")
 }
 location.cancel()
 weather.cancel()
 }
 log("\ndone in $time")
 }
 
 private fun channelWeather(locationChannel: ProducerJob, ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get weather for $locationChannel")
 locationChannel.consumeEach { location ->
 val list = ws.weather(location.lat, location.lng, "EN").execute().body().forecast?.simpleforecast?.forecastday?.take(4).orEmpty()
 list.forEach { send(it) }
 }
 }
 
 private fun channelLocation(ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get location")
 val location = ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 location?.let {
 send(location)
 }
 }

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@Test
 fun testWeather() = runBlocking {
 val ws = retrofitWS("https://my-weather-api.herokuapp.com/")
 val time = measureTimeMillis {
 val location = channelLocation(ws)
 val weather = channelWeather(location, ws)
 weather.consumeEach { w ->
 log("got weather : $w")
 }
 location.cancel()
 weather.cancel()
 }
 log("\ndone in $time")
 }
 
 private fun channelWeather(locationChannel: ProducerJob, ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get weather for $locationChannel")
 locationChannel.consumeEach { location ->
 val list = ws.weather(location.lat, location.lng, "EN").execute().body().forecast?.simpleforecast?.forecastday?.take(4).orEmpty()
 list.forEach { send(it) }
 }
 }
 
 private fun channelLocation(ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get location")
 val location = ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 location?.let {
 send(location)
 }
 }

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@Test
 fun testWeather() = runBlocking {
 val ws = retrofitWS("https://my-weather-api.herokuapp.com/")
 val time = measureTimeMillis {
 val location = channelLocation(ws)
 val weather = channelWeather(location, ws)
 weather.consumeEach { w ->
 log("got weather : $w")
 }
 location.cancel()
 weather.cancel()
 }
 log("\ndone in $time")
 }
 
 private fun channelWeather(locationChannel: ProducerJob, ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get weather for $locationChannel")
 locationChannel.consumeEach { location ->
 val list = ws.weather(location.lat, location.lng, "EN").execute().body().forecast?.simpleforecast?.forecastday?.take(4).orEmpty()
 list.forEach { send(it) }
 }
 }
 
 private fun channelLocation(ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get location")
 val location = ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 location?.let {
 send(location)
 }
 }

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@Test
 fun testWeather() = runBlocking {
 val ws = retrofitWS("https://my-weather-api.herokuapp.com/")
 val time = measureTimeMillis {
 val location = channelLocation(ws)
 val weather = channelWeather(location, ws)
 weather.consumeEach { w ->
 log("got weather : $w")
 }
 location.cancel()
 weather.cancel()
 }
 log("\ndone in $time")
 }
 
 private fun channelWeather(locationChannel: ProducerJob, ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get weather for $locationChannel")
 locationChannel.consumeEach { location ->
 val list = ws.weather(location.lat, location.lng, "EN").execute().body().forecast?.simpleforecast?.forecastday?.take(4).orEmpty()
 list.forEach { send(it) }
 }
 }
 
 private fun channelLocation(ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get location")
 val location = ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 location?.let {
 send(location)
 }
 }

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@Test
 fun testWeather() = runBlocking {
 val ws = retrofitWS("https://my-weather-api.herokuapp.com/")
 val time = measureTimeMillis {
 val location = channelLocation(ws)
 val weather = channelWeather(location, ws)
 weather.consumeEach { w ->
 log("got weather : $w")
 }
 location.cancel()
 weather.cancel()
 }
 log("\ndone in $time")
 }
 
 private fun channelWeather(locationChannel: ProducerJob, ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get weather for $locationChannel")
 locationChannel.consumeEach { location ->
 val list = ws.weather(location.lat, location.lng, "EN").execute().body().forecast?.simpleforecast?.forecastday?.take(4).orEmpty()
 list.forEach { send(it) }
 }
 }
 
 private fun channelLocation(ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get location")
 val location = ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 location?.let {
 send(location)
 }
 }

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@Test
 fun testWeather() = runBlocking {
 val ws = retrofitWS("https://my-weather-api.herokuapp.com/")
 val time = measureTimeMillis {
 val location = channelLocation(ws)
 val weather = channelWeather(location, ws)
 weather.consumeEach { w ->
 log("got weather : $w")
 }
 location.cancel()
 weather.cancel()
 }
 log("\ndone in $time")
 }
 
 private fun channelWeather(locationChannel: ProducerJob, ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get weather for $locationChannel")
 locationChannel.consumeEach { location ->
 val list = ws.weather(location.lat, location.lng, "EN").execute().body().forecast?.simpleforecast?.forecastday?.take(4).orEmpty()
 list.forEach { send(it) }
 }
 }
 
 private fun channelLocation(ws: BlockingWeatherWS) = produce(CommonPool) {
 log("get location")
 val location = ws.geocode("Toulouse,fr").execute().body().results.first().geometry?.location
 location?.let {
 send(location)
 }
 }

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Coroutines - builder (runBlocking, async, launch …) - primitives (delay, measureTime, job…) - communication (deferred, channel, selector, actor …) => Reactive world (RxJava …) => UI (JavaFX, Android …) => Testing (?)

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Further reading https:/ /github.com/Kotlin/kotlinx.coroutines/blob/master/coroutines-guide.md https:/ /github.com/Kotlin/kotlinx.coroutines/blob/master/ui/coroutines-guide-ui.md https:/ /github.com/Kotlin/anko/wiki/Anko-Coroutines https:/ /akarnokd.blogspot.fr/2017/09/rxjava-vs-kotlin-coroutines-quick-look.html?m=1 https:/ /github.com/Kotlin/kotlinx.coroutines/blob/master/reactive/coroutines- guide-reactive.md Coroutines vs RxJava

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Beyond Kotlin Playground https:/ /github.com/Ekito/beyond-kotlin-playground

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What’s next?

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On the road to Kotlin 1.2 https:/ /blog.jetbrains.com/kotlin/2017/08/kotlin-1-2-m2-is-out/ https:/ /blog.jetbrains.com/kotlin/2017/06/early-access-program-for- kotlin-1-2-has-been-started/

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Others stuffs in 1.1 https:/ /kotlinlang.org/docs/reference/whatsnew11.html Gradle Kotlin Scripts https:/ /github.com/gradle/kotlin-dsl Kotlin Native https:/ /github.com/JetBrains/kotlin-native

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Thank you :)