Opaque types

Magda Stożek

@magdastozek

Get more clarity with

The perfect model

Precise
Readable
Prevents mistakes

Scala 2

Type aliases

Refined types

Value classes

type Age = Int

case class Age(value: Int) extends AnyVal

type Age = Int Refined Positive

Opaque type aliases

Demo:

why "opaque"
how to add API
- object methods
- instance methods
bounds

Summary

Advantages:

simple and clear
no overhead
opaque

Disadvantages:

no API (*unless bounds)
no pattern matching
no toString/equals overriding

Read more

Official documentation: https://docs.scala-lang.org/scala3/reference/other-new-features/opaques.html

Demo code: https://github.com/magdzikk/opaque-types

Questions?

  opaque type EndOfPresentation = TimeToAskQuestions

@magdastozek

http://bit.ly/magda-scalalove

http://bit.ly/opaque-types