Kotlin's Experimental features (from Kotlin Everywhere Seoul 2019 event)

My notes from Kotlin Everywhere Seoul 2019 event

Experimental Features

inline class

• avoids extra object allocation
• wrapper for only one value, no mutable property

Contract

• allows to share extra information about the function behaviors with the compiler.
• Why can't compiler infer such information?
  • the inferred information...
    • can be implicitly change
    • can break the code
• provides explicit behavior for the compiler
• DSL will change (syntax) in the future

Immutable Collections

• (before) despite it is read-only, the content can be changed by others who has the access to the reference.
• (after the change) there will be a new interface added "PersistentList" and it supports modification.
• ImmutableList is going to be "truly immutable"
• List that is created by PersistentList, shares the same data structure with the List.
• (side note) Similar languages like Scala, shares the same concepts about the immutable collections.

Flows

• what is it? → suspend-based reactive stream
• reactive stream vs coroutine
  • if you have streams of events, data ⇒ reactive stream (Flow)
  • asynchronous programming ⇒ coroutine
• Integration with RxJava
  • Publisher < - > Flow
  • interchangeable
• Back pressure: automatically works
• Flows brings reactive streams to coroutine library.
• it is going to be stable REAL SOON

Multi-platform projects

• what is it? → shares the common code between different platforms / shares business logic
• it is NOT the concept that has only one set of code for every platform.
• common code
  • can define expect for the common code
  • define actual for platform-specific codes to implement using their own platform languages
  • can use other multi-platform libraries

Side-notes

• 12/4-6 KotlinConf in Copenhagen
  • expect some cool presentations about the multi-platform projects

Presentation slide

https://speakerdeck.com/svtk/whats-new-in-kotlin