I have a projection that's id needs to be a String, but in the entity it's coming from it's an Int (...

# komapper

[dave08]

I have a projection that's id needs to be a String, but in the entity it's coming from it's an Int (in a value class), is there any way to map the value to the projection? Here I can't really cast it to Column<String, String> because it's not and I can't make an extension either...

[Toshihiro Nakamura]

Create a custom function.

private fun cast(
    expression: ColumnExpression<*, *>,
): ColumnExpression<String, String> {
    val name = "cast"
    val o1 = Operand.Column(expression)
    return columnExpression(String::class, name, listOf(o1)) {
        append("$name(")
        visit(o1)
        append(" as char)")
    }
}

You can use the above function as follows.

val query = QueryDsl.from(e)
    .where { e.employeeName startsWith "S" }
    .selectAsAddress(
        version = e.version,
        addressId = e.employeeId,
        street = cast(e.version),
    )