Render from Another

Module

• The core module:

  "io.kevinlee" %% "extras-render" % "0.49.0"

or for Scala.js:

• The core module:

  "io.kevinlee" %%% "extras-render" % "0.49.0"

contramap

If you have a Render[A] and know how to B => A, you can get Render[B] out of the box with contramap!

import extras.render.Render
import extras.render.syntax._

final case class Id(value: Int) extends AnyVal

/*
 * Get `Render[Id]` from `Render[Id]` with `Id => Int` (i.e. `Id.value`)
 */
implicit val renderId: Render[Id] =
  Render[Int].contramap(_.value) // Render[Int] is already provided by extras.
// renderId: Render[Id] = extras.render.Render$RenderOps$$$Lambda$9114/0x0000000802660840@43b36ea

Id(123).render
// res1: String = "123"

Contravariant

If your project uses cats, you get Contravariant[Render] out of the box! With Contravariant[Render], you can get Render[B] from Render[A] if you know how to B => A.

import cats._

import extras.render.Render
import extras.render.syntax._

final case class Id(value: Int) extends AnyVal

/*
 * With `Contravariant[Render]`,
 *   get `Render[Id]` from `Render[Id]` with `Id => Int` (i.e. `Id.value`)
 */
implicit val renderId: Render[Id] =
  Contravariant[Render].contramap(Render[Int])(_.value) // Render[Int] is already provided by extras.
// renderId: Render[Id] = extras.render.Render$$anon$1$$Lambda$9115/0x0000000802660c40@1f8bdca4

Id(123).render
// res3: String = "123"

info

Contravariant