How to bind an enum to a playframework form? - scala

Question

I have an enum of the form:
object MatchFilterType extends Enumeration {
type MatchFilterType = Value
val gt = Value("gt")
val lt = Value("lt")
val eq = Value("eq")
}
Trying to create a form val in my controller:
case class SearchRequest(mft: MatchFilterType, queryText: String, locations: List[String])
val searchForm: Form[SearchRequest] = Form(
mapping(
"mft" -> ????????,
"queryText" -> nonEmptyText,
"locations" -> list(text)
)(SearchRequest.apply)(SearchRequest.unapply)
)
I am using play 2.6.x for this project.
How do I map my enumeration in my Form val?

Answer 1

First create an implicit Formatter that uses the enums withName method which takes a string and turns it into an enum:
implicit def matchFilterFormat: Formatter[MatchFilterType] = new Formatter[MatchFilterType] {
override def bind(key: String, data: Map[String, String]) =
data.get(key)
.map(MatchFilterType.withName(_))
.toRight(Seq(FormError(key, "error.required", Nil)))
override def unbind(key: String, value: MatchFilterType) =
Map(key -> value.toString)
}
Then use Forms.of to create a FieldMapping:
Form(...,
"mft" -> Forms.of[MatchFilterType],
...)
Bear in mind that MatchFilterType.withName(_) will thrown an exception if the string is not an enum member, so update the bind method to handle this as you need.

Answer 2

A more generic approach:
def enumerationFormatter[E <: Enumeration](enum: E): Formatter[E#Value] = new Formatter[E#Value] {
override def bind(key: String, data: Map[String, String]): Either[Seq[FormError], E#Value] =
data.get(key).map(s => enum.withName(s)).toRight(Seq(FormError(key, "error.required", Nil)))
override def unbind(key: String, value: E#Value): Map[String, String] = Map(key -> value.toString)
}
Which can then be used like:
object TestValues extends Enumeration {
type TestValue = Value
val Test: TestValue = Value
}
case class MyForm(testValue: TestValue)
object MyForm {
implicit val testValueFormatter: Formatter[TestValue] = enumerationFormatter(TestValues)
val form = Form(mapping("testValue" -> of[TestValue])(MyForm.apply)(MyForm.unapply))
}