scala smart constructor with value classes / published by https://github.com/dacr/code-examples-manager #ed5363d3-527d-4e97-9e03-229998e4424e/d1f3da63bb8aa590f6d0e36914986ee63c3b506a

scala-feature-smart-constructor-with-value-class.sc

// summary : scala smart constructor with value classes
// keywords : scala, adt, language-feature, smart-constructor, value-class, @testable
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : ed5363d3-527d-4e97-9e03-229998e4424e
// created-on : 2022-06-15T20:38:16+02:00
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file

// ---------------------
//> using scala "3.4.2"
//> using objectWrapper
// ---------------------

// written after [John De Goes - 12 Steps To Better Scala (Part I)](https://youtu.be/71yhnTGw0hY)

// ----------------------------------------------------------------
// Smart constructor to make it impossible to define illegal state
// See also :
// - https://github.com/fthomas/refined
// - http://fthomas.github.io/talks/2016-05-04-refined
// - https://kwark.github.io/refined-in-practice/

class Email private(val value: String) extends AnyVal:
  override def toString: String = value

object Email {
  def checkEmail(input:String):Boolean = {
    // https://howtodoinjava.com/java/regex/java-regex-validate-email-address/
    input.matches("^[a-zA-Z0-9_!#$%&’*+/=?`{|}~^.-]+@[a-zA-Z0-9.-]+$")
  }
  def fromString(value: String):Option[Email] = {
    if (checkEmail(value)) Some(Email(value))
    else None
  }
}

// The only way to create email instances...
val email = Email.fromString("[email protected]")
email.foreach(println)

// Email("truc machin") // DO NOT COMPILE