Question

I have three models

class Vehicle < ActiveRecord::Base
 has_one:driver ,:through=>:vehicle_driver
end

class Vehicle_Driver < ActiveRecord::Base
 belongs_to:vehicle
 belongs_to:driver
end

have only vehicle_id and driver_id

class Driver < ActiveRecord::Base
 has_one:vehicle_driver
end

I want to do is

• register the vehicles independently

• register the Drivers independently

• then assign driver to vehicle such that only one driver can be assigned to one vehicle and vice versa

and further

• if I assign driver to another vehicle its early relation must be deleted

Is this possible from above relationship …?????

Any help will be appreciated..

Thanks In Advance

Answer 1

1. Why the intermediate class, it contradicts your requirements, so remove it.

2. So just let both models Vehicle and Driver use has_one of the other. It generates a duplicate relationship that could lead to problems, if they are not pointing to each other. So the best is to have only one ‘has_one’-relationship, and do @vehicle.find_by_driver to test if a driver already has a vehicle assigned to it.

3. When you save a relationship, also update the other relation:
   3a @vehicle.driver = @driver
   3b @vehicle.driver.vehicle = @vehicle # to force make them point to each other.

4. In the Vehicle model, add a method or scope to return a list of vehicles where driver is nil.
   4a Vehicle.all.where(:driver.nil?) # from my head, just to give an idea

If you want to remove a relationship for a vehicle, do
5a @vehicle.driver.vehicle = nil
5b @vehicle.driver = nil

Hope this helps you in the right direction.