How to implement enums in scala slick 3?

Question

This question has been asked and answered for slick 1 and 2, but the answers don't seem to be valid for slick 3.

Attempting to use the pattern in How to use Enums in Scala Slick?,

object MyEnumMapper {
  val string_enum_mapping:Map[String,MyEnum] = Map(
     "a" -> MyEnumA,
     "b" -> MyEnumB,
     "c" -> MyEnumC
  )
  val enum_string_mapping:Map[MyEnum,String] = string_enum_mapping.map(_.swap)
  implicit val myEnumStringMapper = MappedTypeMapper.base[MyEnum,String](
    e => enum_string_mapping(e),
    s => string_enum_mapping(s)
  )
}

But MappedTypeMapper has not been available since slick 1, and the suggested MappedColumnType for slick 2 is no longer available, despite being documented here.

What's the latest best practice for this?

`MappedColumnType` is still availible and I use it frequently in slick 3.0 — Krever, Jul 30 '15 at 06:44

score 19 · Accepted Answer · answered Jul 30 '15 at 06:55

19

What exactly do you mean by MappedColumnType is no longer available? It comes with the usual import of the driver. Mapping an enum to a string and vice versa using MappedColumnType is pretty straight forward:

object MyEnum extends Enumeration {
  type MyEnum = Value
  val A = Value("a")
  val B = Value("b")
  val C = Value("c")
}

implicit val myEnumMapper = MappedColumnType.base[MyEnum, String](
  e => e.toString,
  s => MyEnum.withName(s)
)

answered Jul 30 '15 at 06:55

Roman

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My bad, I'm not sure now why I thought that was the case. – kbanman Jul 31 '15 at 08:12
The implicit mapper should be located inside the enum object though, no? – Cedric Reichenbach Mar 01 '18 at 14:11
2

@CedricReichenbach It's just an example. You can place it wherever you like, just make sure it is in scope for the compiler when needed. – Roman Mar 01 '18 at 15:56

score 2 · Answer 2 · answered Oct 03 '18 at 06:12

2

A shorter answer so that you don't need to implement myEnumMapper yourself:

import play.api.libs.json.{Reads, Writes}

object MyEnum extends Enumeration {
  type MyEnum = Value
  val A, B, C = Value // if you want to use a,b,c instead, feel free to do it

  implicit val readsMyEnum = Reads.enumNameReads(MyEnum)
  implicit val writesMyEnum = Writes.enumNameWrites
}

answered Oct 03 '18 at 06:12

yiksanchan

1,890
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3

How does this work? Does Slick pick up JSON Reads automatically somehow? – Thilo May 20 '19 at 06:39

How to implement enums in scala slick 3?

2 Answers2