rails scope and joins
activerecord, ruby-on-rails, sql
Solution
I am assuming that you mean this: Car has `radio_id`, User has `car_id`, since a radio has many cars and car has one user. The table with the foreign key always is on the belongs_to end of the relationship.
Without really knowing the structure you're looking for, something like the following should work:
scope :with_cd_player, joins(:cars).where('cars.radio_id is not null')
if there is a category column on the radio, the following would work.
scope :with_cd_player, joins(:car => :radio).where('cars.radio_id is not null').where("radios.category = 'cd_player'")
For Rails Version >= 4:
scope :with_cd_player, -> { joins(:cars).where.not(cars: { radio_id: nil }) }
Problem
I have tried everything i thought would work for this and am turning up nothing. in rails 3, I need to find all users with a cd player in their car. A car has one user and one radio, and a user belongs to a car, and a radio has many cars. I am stumbling on how I would perform this search via a scope in the user model. ``` class User belongs_to :car class Car belongs_to radio has_one :user, :dependent => destroy class Radio has_many :cars ```