header/impl关键字在kotlin中是什么意思? [英] What does header/impl keyword mean in kotlin?

问题描述

刚才，当我探索Kotlin github存储库时，我发现了一些有趣的东西:Kotlin现在似乎有一个header关键字.

CollectionsH.kt :

 open header class ArrayList<E> : MutableList<E> {

 //...

 header inline fun <reified T> Array<out T>?.orEmpty(): Array<out T>

是什么意思?是一些公共可用功能还是内部功能来帮助stdlib开发?

---

似乎有一个impl关键字与标头结合使用.那是什么?

解决方案

更新2:

多平台项目支持已发布.

• 链接到公告
• KotlinConf 2017的多平台应用程序

更新1:

在Kotlin的多平台项目的预览版本中，impl和header关键字已由actual和expect替换.

可以在此处或此处找到官方文档 GitHub 永久链接

---

在此视频在14:28进行了讨论.

从幻灯片:

基本上，当为跨多个平台(JVM，JS和本机)工作的模块编写接口时，将使用header.在为特定平台编写实现时，将使用impl关键字.

Just moments ago when I was exploring the Kotlin github repo, I found something interesting: Kotlin now seems to have a header keyword.

CollectionsH.kt:

 open header class ArrayList<E> : MutableList<E> {

 //...

 header inline fun <reified T> Array<out T>?.orEmpty(): Array<out T>

What does it mean? Is it some public available feature or a internal feature to help stdlib development?

---

EDIT: There seems to be a impl keyword that work in conjunction with header. What's that?

解决方案

UPDATE 2:

Multiplatform project support has been released.

• Link to the announcement
• Multiplatform application for KotlinConf 2017

UPDATE 1:

The impl and header keywords have been replaced by actual and expect in the preview release of multiplatform projects for Kotlin.

The official documentation can be found here or at this GitHub permalink

---

It was talked about in this video at 14:28.

From the slides:

Basically, header will be used when writing interfaces for modules that work across multiple platforms (JVM, JS, and Native). Theimpl keyword will be used when writing an implementation for a specific platform.

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