Extra columns in bridging table

[thedjdoorn]

For many-to-many relations, the creation of bridging tables is often necessary. In some cases, these relations may require some extra data. To use the wiki example:

// create film
val film = transaction {
   StarWarsFilm.new {
    name = "The Last Jedi"
    sequelId = 8
    director = "Rian Johnson"
  }
}

//create actor
val actor = transaction {
  Actor.new {
    firstname = "Daisy"
    lastname = "Ridley"
  }
}

//add reference
transaction {
  film.actors = SizedCollection(listOf(actor))
}

Suppose one were to add extra information to this relation, such as the role played, then the current solution would be to have a Role-like entity, referencing the film and actor, and containing the extra data. Now you have a problem referencing Actor using the via keyword. Wouldn't the following approach be preferable? Why is this not possible?

// The StarWarsFilmActors table now contains a role field
object StarWarsFilmActors : Table() {
    val starWarsFilm = reference("starWarsFilm", StarWarsFilms).primaryKey(0)
    val actor = reference("actor", Actors).primaryKey(1)
    val roleName = varchar("50")
}

transaction {
    film.actors.push(actor, {roleName = "Rey"})
}