[英]Scala: Refined Algebraic Data Types
o/
這可能是一個相當有趣的問題,並且可能會激發你們的創造力。
我想以一種我可以的方式對貨幣進行建模:
val amount: Float Refined Positive
在一個實現中執行此操作的一個子集很容易,但我發現創建一種允許類似以下內容的類型非常困難:
def doSomething(currency: Currency): Unit {
currency match {
case BITCOIN => println("Oh, a cryptocurrency! And it is ${currency.amount} ${currency.code}!"
case EURO => println("So we are from Europe, eh?")
}
}
doSomething(new Currency.BITCOIN(123f)) // yielding "Oh, a cryptocurrency! And it is 123 BTC!"
val euro = new Currency.EURO(-42f) // compile error
我希望我清楚地表達了我的意圖。 如果有圖書館這樣做,我很高興有人指出它,盡管我希望從自己的思考中學到一些東西。
你的意思是這樣的嗎?
import eu.timepit.refined.api.Refined
import eu.timepit.refined.auto._
import eu.timepit.refined.numeric.NonNegative
import eu.timepit.refined.string.MatchesRegex
sealed trait Currency extends Product with Serializable {
def amount: Currency.Amount
def code: Currency.Code
}
object Currency {
type Amount = BigDecimal Refined NonNegative
type Code = String Refined MatchesRegex["[A-Z]{3}"]
final case class Euro(amount: Amount) extends Currency {
override final val code: Code = "EUR"
}
final case class Dollar(amount: Amount) extends Currency {
override final val code: Code = "USD"
}
}
def doSomething(currency: Currency): Unit =
currency match {
case Currency.Euro(amount) => println(s"Euro: € ${amount}")
case _ => println(s"Somenthing else with code ${currency.code} and amount ${currency.amount}")
}
這有效:
doSomething(Currency.Dollar(BigDecimal(10)))
// Somenthing else with code USD and amount 10
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