linking models ruby on rails

Question

Hi I have 3 models: user, seller and cars

i want the user to be able to choose a car from a seller and this gets added to the user's shopping list.

I have something like this in my car controller:

 @user = User.find(params[:user])
  @seller = Seller.find(params[:seller])

  @car = @user.cars.build(params[:car])

but the seller isnt being added. how can I do this please?

Btw I have this:

class Car < ActiveRecord::Base
  belongs_to :user
  belongs_to :seller
end

in my Model for car

Answer 1

@car.seller = @seller

Answer 2

add:

@car.seller = @seller after you build the car. Then @car.save

Build doesn't know about @seller, you need to tell the car that it has a seller. It only really knows that there's a user because you created the car from the user.

You could also do:

@car = Car.new
@car.seller = @seller
@car.user = @user

Answer 3

If you ensure that the fields in your form that produce params[:car] includes a field for the seller's id you won't need to change your controller at all.

Eg:

<% fields_for :car, @seller.cars.build do |car_form| %>
 <%= car_form.hidden_field :seller_id
 ... more fields for car form ...

<% end %>