Find select field

I have nations with settlements with members, I’m trying to get all of the members of the nation through the settlements.

        val members: List<SLPlayerId> = Settlement.COL
            .find(Settlement::nation eq id).projection(Settlement::members)
            .map { it.members }
            .flatten()

This gives me this error:

[08:01:22 ERROR]: [SLCore] [ACF] Caused by: com.fasterxml.jackson.module.kotlin.MissingKotlinParameterException: Instantiation of [simple type, class net.starlegacy.slcore.mongo.Settlement] value failed for JSON property territory due to missing (therefore NULL) value for creator parameter territory which is a non-nullable type
[08:01:22 ERROR]: [SLCore] [ACF]  at [Source: de.undercouch.bson4jackson.io.LittleEndianInputStream@24d5132b; pos: 148] (through reference chain: net.starlegacy.slcore.mongo.Settlement["territory"])

Is there a way to get the value without attempting to construct the whole object?

[zigzago]

You have two options:

1. project into Document (ie Map):

val members: List<SLPlayerId> = Settlement.COL
            .withDocumentClass<Document>()
            .find(Settlement::nation eq id)
            .projection(Settlement::members)
            .map { it.getString(Settlement::members.name) }
            .flatten()

This will not work if members is a complex object.

1. project into dedicated object

data class SettlementWithMembersOnly(val members: Array<Array<SLPlayerId>>)

val members: List<SLPlayerId> = Settlement.COL
            .withDocumentClass<SettlementWithMembersOnly>()
            .find(Settlement::nation eq id)
            .projection(Settlement::members)
            .map { it.members }
            .flatten()

Also I’m going to add a projection extension method, in order to project “out of the box” one, two or three fields.

HTH

[MicleBrick]

Okay, hopefully you’ll find what I came up with helpful 😃