Exposed: How To: Many-to-Many and DAO?

[gcscaglia]

First, I've searched everywhere but couldn't find a forum / detailed guide on Exposed framework so I'm resorting to post an issue here.

How do you model a many-to-many relationship using the DAO (Entities) method? Take these models:

package abcd

import org.jetbrains.exposed.dao.*
import org.jetbrains.exposed.sql.*

object Tags : IntIdTable(name = "tags") {
    val name = text("name")
}

object Posts : IntIdTable(name = "posts") {
    val uploadDate = datetime("upload_date")
}

object PostsTags : Table(name = "posts__tags") {
    val post = reference("post", Posts).primaryKey(0)
    val tag = reference("tag", Tags).primaryKey(1)
}

class Tag(id: EntityID<Int>) : IntEntity(id) {
    companion object : IntEntityClass<Tag>(Tags)

    var name by Tags.name
}

class Post(id: EntityID<Int>) : IntEntity(id) {
    companion object : IntEntityClass<Post>(Posts)

    var uploadDate by Posts.uploadDate
    val tags by Tag referrersOn PostsTags.tag // Obviously does not work. But how else?
}

How can I modify the Post entity so it has a tags property returning all tags associated to it through PostsTags? val tags by Tag referrersOn PostsTags.tag obviously doesn't work, and I couldn't find any similar alternative constructs.

In case such a scenario is not supported, how could one implement it? By looking on Referrers implementation I've got a general grasp on how to do it, but I'm struck at how to return a SizedIterable of tags from the results of a native SQL DSL query. Is there any mapping from SizedIterable<ResultRow> to SizedIterable<Entity>?

[Tapac]

Maybe this will help:
val tags by Tag via PostsTags

[gcscaglia]

Seems I was looking at it from the wrong direction. English is not my mother tongue, I had assumed via to meant something else altogether. Thank you very much.

I could send a pull request extending the current DAO samples to show via usage. Would it be desirable?

[Tapac]

Ofc it will be great to improve documentations and samples. Will wait for your PR.