runBlocking and other high-level coroutine utilities are not in the Kotlin standard library, but instead are a part of the library kotlinx.coroutines. To use this library in your project you must download its binaries and add a dependency on them to the project. Usually declaring a library dependency is a line or couple of lines … Read more
Code fun main(args: Array<String>) { data class Combine(val alpha: String, val num: Int) val list = arrayListOf(Combine(“a”, 1), Combine(“b”, 2), Combine(“c”, 3), Combine(“a”, 4)) val mapOfList = list.associateBy ( {it.alpha}, {it.num} ) println(mapOfList) val changed = list .groupBy ({ it.alpha }, {it.num}) println(changed) } Output {a=4, b=2, c=3} {a=[1, 4], b=[2], c=[3]} How it works … Read more
Kotlin doesn’t have a built-in List<T>.tail() function, so implementing your own extension function is the only way. Although your implementation is perfectly fine, it can be simplified a bit: fun <T> List<T>.tail() = drop(1) Or, instead of extension function, you can define an extension property: val <T> List<T>.tail: List<T> get() = drop(1) val <T> List<T>.head: … Read more
The issue is most likely that you forgot to depend on the reflection libraries which were needed for the reflective functions of Kotlin. On the Java platform, the runtime component required for using the reflection features is distributed as a separate JAR file (kotlin-reflect.jar). This is done to reduce the required size of the runtime … Read more
Collect will collect every value , and CollectLatest will stop current work to collect latest value, The crucial difference from collect is that when the original flow emits a new value then the action block for the previous value is cancelled. flow { emit(1) delay(50) emit(2) }.collect { value -> println(“Collecting $value”) delay(100) // Emulate … Read more
As far as I am concerned, you should put them into a utility file, as you did in Java code base before. But mention, you no longer need to put them into a class. Top-level functions are the best choice. You can refer to the kotlin standard library or some open source projects like anko, … Read more
tl;dr: https://youtrack.jetbrains.com/issue/KT-22044 is a good fit regarding this issue. I will cite what Intellij IDEAs inspection called “Leaking ‘this’ in constructor” says about this: This inspection reports dangerous operations inside constructors including: Accessing a non-final property in constructor Calling a non-final function in constructor Using this as a function argument in a constructor of a … Read more
You should make the function go an extension function of CoroutineScope: fun main() = runBlocking { go() go() go() println(“End”) } fun CoroutineScope.go() = launch { println(“go!”) } Read this article to understand why it is not a good idea to start in a suspend functions other coroutines without creating a new coroutineScope{}. The convention … Read more
You can use answers: val otm: ObjectToMock = mockk() every { otm.methodToCall(any(), any())} answers { secondArg<(String) -> Unit>().invoke(“anything”) } otm.methodToCall(“bla”){ println(“invoked with $it”) //invoked with anything } Within the answers scope you can access firstArg, secondArg etc and get it in the expected type by providing it as a generic argument. Note that I explicitly … Read more
with is used to access an object’s members and methods without having to refer to the object once per access. It is (mostly) for abbreviating your code. It is frequently used when constructing an object: // Verbose way, 204 characters: var thing = Thingummy() thing.component1 = something() thing.component2 = somethingElse() thing.component3 = constantValue thing.component4 = … Read more