Hey there! Is it possible to access attributes con...

# exposed

[Marc]

Hey there!
Is it possible to access attributes contained in a many-to-many relationship in Exposed?
In particular, I have the following classes:

class ShiftDao(id: EntityID<Int>) : IntEntity(id) {
    companion object : IntEntityClass<ShiftDao>(Shifts)

    var date by Shifts.date
    var startTime by Shifts.startTime
    var endTime by Shifts.endTime
    var text by Shifts.text
    var isEvent by Shifts.isEvent

    var client by ClientDao optionalReferencedOn Shifts.clientId
    var schedule by ScheduleDao referencedOn Shifts.scheduleId
    var assignees by EmployeeDao via ShiftAssignees
    
}

object ShiftAssignees : IntIdTable() {

    val shiftId = reference("shift_id", Shifts, fkName = "fk_shiftass_shift_id")
    val employeeId = reference("employee_id", Employees, fkName = "fk_shiftass_employee_id")

    val attended = bool("attended").default(true)
    
}

My goal is to get not only all EmployeeDao's out of the assignments but also the "attended" attribute.
Is this possible?

[Chantal Loncle]

Hi @Marc A way to get additional columns back is currently in the works. It would not be necessary to create an arbitrary id column for the link table (or require it to be an IdTable). Please consider tracking EXPOSED-320 for updates on completion.

[Marc]

So there's no way to reference the ShiftAssignees within the ShiftDao?

[Chantal Loncle]

I've seen users resort to a few workarounds, for example creating a fake id as the table constraint then creating an associated entity class. Instead of using via, each field would be treated like a regular reference etc, but it doesn't seem very straightforward.

An alternative I experimented with, before starting the design for the feature, involves using CompositeIdTable to define the link table. With that you could define an entity ShiftAssigneesDAO class with a single attended field and still use via in ShiftDAO, as well as an additional field for attended.
The only caveat with this approach is that the via field (assignees) could only be used for retrieiving/getting. Instances of ShiftAssigneesDAO would have to be created as usual with new() and a CompositeID of the 2 reference column values.
Here's an example of this approach in the tests.