Introduction to Optics

optics.sc

//> using scala "3.3.0"
//> using dep "dev.optics::monocle-core:3.2.0"
//> using dep "dev.optics::monocle-macro:3.2.0"

import monocle.syntax.all._

case class Product(id: String, name: String, price: Double)
case class Shelf(id: String, product: Product)
case class Display(id: String, kind: "Ambient" | "Chilled", shelves: List[Shelf] )
case class Alley(id: String, displays: List[Display])
case class Shop(alleys: List[Alley])

val water = Product("1", "Bottle of water", 6.99)
val milk = Product("2", "Milk 1l", 3.85)
val cheese = Product("3", "Cheese", 7.99)
val ham = Product("4", "Ham", 9.99)

val shop = Shop(
  alleys = List(
    Alley(
      id = "1",
      displays = List(
        Display("1", "Ambient", List(Shelf("1", water), Shelf("2", milk))),
        Display("2", "Chilled", List(Shelf("3", cheese), Shelf("4", ham)))
      )
    )
  )
)

val discounted = 
  shop
    .focus(_.alleys)
    .each
    .refocus(_.displays)
    .each
    .refocus(_.shelves)
    .each
    .refocus(_.product.price)
    .modify(_ * 0.9)

println(discounted)

fair nuff, although the example already uses union types 😅

That's also true! I planned to update the post with a clarification anyway 😁