lu4nm3

scala> new EmailAddress("@example.com") {}
<console>:15: error: illegal inheritance from sealed class EmailAddress
       new EmailAddress(""){}

lu4nm3

scala> class EvilEmailAddress(address: String) extends EmailAddress(address)
<console>:14: error: illegal inheritance from sealed class EmailAddress
       class EvilEmailAddress(address: String) extends EmailAddress(address)

lu4nm3

sealed abstract case class EmailAddress(emailAddress: String)

lu4nm3

class EvilEmailAddress(address: String) extends EmailAddress(address)

EmailClient.sendEmail(from = new EvilEmailAddress("[email protected]"), to = new EvilEmailAddress("@example.com")) {
  ...
}

lu4nm3

new EmailAddress(emailAddress) {}

lu4nm3

scala> EmailAddress("[email protected]").map(_.copy(emailAddress = "@example.com"))
<console>:13: error: value copy is not a member of EmailAddress
       EmailAddress("[email protected]").map(_.copy(emailAddress = "@example.com"))
       ^

lu4nm3

abstract case class EmailAddress(emailAddress: String)

lu4nm3

scala> EmailAddress("[email protected]").map(_.copy(emailAddress = "@example.com"))
res0: scala.util.Either[String,Either[String,EmailAddress]] = Right(Left(Invalid email address))

scala> for {
  |   e1 <- EmailAddress("[email protected]")
  |   e2 <- e1.copy(emailAddress = "@example.com")
  | } yield e2
res1: scala.util.Either[String,EmailAddress] = Left(Invalid email address)

lu4nm3

case class EmailAddress(emailAddress: String) {
  def copy(emailAddress: String = emailAddress): Either[String, EmailAddress] = {
    EmailAddress(emailAddress)
  }
}

lu4nm3

scala> val emailAddress = EmailAddress("[email protected]")
emailAddress: Either[String,EmailAddress] = Right(EmailAddress([email protected]))

scala> emailAddress.map(_.copy(emailAddress = "@example.com"))
res0: scala.util.Either[String,EmailAddress] = Right(EmailAddress(@example.com))