<enumeration>

XML Schema Part 0: Primer:

The enumeration facet limits a simple type to a set of distinct values. For example, we can use the enumeration facet to define a new simple type called USState, derived from string, whose value must be one of the standard US state abbreviations:

<xsd:simpleType name="USState">
  <xsd:restriction base="xsd:string">
    <xsd:enumeration value="AK"/>
    <xsd:enumeration value="AL"/>
    <xsd:enumeration value="AR"/>
    <!-- and so on ... -->
  </xsd:restriction>
</xsd:simpleType>

We can use case objects to express these restrictions. Here’s what scalaxb generates:

trait USState

object USState {
  def fromXML(seq: scala.xml.NodeSeq): USState = fromString(seq.text)

  def fromString(value: String): USState = value match {
    case "AK" => AK
    case "AL" => AL
    case "AR" => AR
    case "DE" => DE

  }
}

case object AK extends USState { override def toString = "AK" }
case object AL extends USState { override def toString = "AL" }
case object AR extends USState { override def toString = "AR" }