Rails Associations - Simple Join

Question

New working with Rails 4 and have a question on associations.

Let's say I have a Car

create_table "cars", force: true do |t|
    t.string   "name"
    t.integer  "owner_id"
    t.integer  "mechanic_id"

end

And I have some users which roles are "Owner" and "Mechanic"

create_table "users", force: true do |t|
    t.string   "name"
    t.integer  "role_id"
end

Now when I get a list of Cars, I want the names of the Owner and the Mechanic...

I know this sounds easy but i've been banging my head around the associations and not getting anywhere.

I want to display this:

name   owner   mechanic
Ferari Paul    James

with this schema

User
id  first  role
1   Paul   owner
2   James  mechanic

Car
name     owner_id  mechanic_id
Ferrari  1          2

Any help would be much appreciated.

Answer 1

You have two associations to the same model. So in your model/car.rb write:

class Car < ActiveRecord::Base
  belongs_to :owner, class_name: 'User'
  belongs_to :mechanic, class_name: 'User'
end

and you can use car.owner.name and car.mechanic.name.
See rails guide on associations