```open class Human class Men Human class Women Human val hu kotlinlang #announcements

Channels

100daysofkotlin

100daysofkotlin-2021

algolialibraries

android-architecture

android-databinding

androidgithubprojects

androidx-xprocessing

arrow-contributors

beepiz-libraries

cincinnati-user-group

codemash-precompiler

codingconventions

competitive-programming

competitivecoding

compose-android

compose-desktop

compose-ui-showcase

connect-audit-events

cscenter-course-2016

domain-driven-design

effective-kotlin

effectivekotlin

embedded-kotlin

event21-community-content

fb-internal-demo

fluid-libraries

framework-elide

getting-started

github-workflows-kt

graviton-browser

image-processing

intellij-plugins

intellij-tricks

introduce-yourself

java-to-kotlin-refactoring

jhipster-kotlin

jvm-ir-backend-feedback

k2-early-adopters

kotest-contributors

kotlin-by-example

kotlin-data-storage

kotlin-foundation

kotlin-in-action

kotlin-multiplatform-contest

kotlin-pakistan

kotlinforbeginners

kotlingforbeginners

kotlinprogrammers

kotlintest-devs

kotlinultimatechallenge

kotlinx-datetime

lambdaworld_cadiz

language-evolution

language-proposals

leedskotlinusergroup

library-development

machinelearningbawas

myndocs-oauth2-server

navigation-architecture-component

ohio-kotlin-users

pattern-matching

pocketgitclient

practical-functional-programming

prozis-android-backup

python-contributors

realworldkotlin

refactoring-to-kotlin

refreshversions

russian-kotlinasfirst

skia-wasm-interop-temp

sofl-user-group

spring-security

squarelibraries

stayhungrystayfoolish

strife-discord-lib

swagger-gradle-codegen

swiss-user-group

tricity-kotlin-user-group

Title

d

dasz

03/16/2018, 5:28 PM

open class Human() 
class Men:Human()
class Women:Human()
val humanNation = asList(Women(), Man())

val womenForMe = humanNation.firstOrNull{ it is Women} as Women?

any shorter form? thank you @agrosner for the help the solution is

inline fun <reified K:T, T> List<T>.firstOrNull(): K? = firstOrNull { it is K} as K?

usage

val womenForMe : Women = humanNation.firstOrNull()

🤨 2

z

zpearce

03/16/2018, 5:35 PM

I don't think you need the cast to

Women?

a

agrosner

03/16/2018, 5:35 PM

It might return a base class that's why he's casting

👆 3

f

fred.deschenes

03/16/2018, 5:36 PM

there's

filterIsInstance

but that's not shorter and will go through the whole list

s

Shawn

03/16/2018, 5:36 PM

I assumed there was some base

Human

type that was being implemented

👏 1

k

kristofdho

03/16/2018, 5:36 PM

not with a sequence and

.first()

a

agrosner

03/16/2018, 5:36 PM

Make an extension inline reified method

Then you can just call firstOrNull<Woman>

like this:

inline fun <reified T> List<T>.singleOrNull(): T? = singleOrNull { it is T} as T?

that might work. not sure what kind of object you're operating on

d

dasz

03/16/2018, 5:58 PM

let me check, it could be a solution

nope it doesn't help much as it should operate on Human and Women:Human class, like <T:K, K>

ok, got it, thx @agrosner using your solution I found the way,

inline fun <reified K:T, T> List<T>.firstOrNull(): K? = firstOrNull { it is K} as K?

a

agrosner

03/16/2018, 6:57 PM

great!

2 Views

#announcements Join Slack