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Add the ability to override how enums are mapped to the database.

See original GitHub issue

Use case

I would like to able to map enums in Kotlin to integers in the database. The pre-existing databases that I am developing against (in SQL Server) have all the enum-like columns stored as integers often with a backing constraint table.

Describe the solution you’d like

I would like to be able to provide a custom DataType converter to map the enums but it does not work. The komapper-processor is currently hard-coded to prioitise mapping enums to strings.


  • Komapper: 1.0.0-RC1
  • Kotlin: 1.6.21
  • JVM: JDK 14.0.1
  • JDBC Driver or R2DBC Driver:
  • Database: SQL Server 2014
  • OS: Windows 10

Issue Analytics

  • State:closed
  • Created a year ago
  • Comments:5 (3 by maintainers)

github_iconTop GitHub Comments

donard-commedaghcommented, May 23, 2022

That’s a good idea, I’ve only just read up on value classes in the last week and haven’t used them anywhere yet. As a temporary fix, I can live without the exhaustive when(enum) and enum.values()

Thank you for the excellent work developing Komapper.

nakamura-tocommented, May 23, 2022

By the way, you can use value class instead of enum class. For example, the following code works with Komapper 1.0.0-RC1:

value class Color(val value: Int) {
    companion object {
        val BLUE = Color(0)
        val RED = Color(1)
        val YELLOW = Color(2)

data class Pencil(
    val id: Int,
    val color: Color
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