Question

I have a seat object that has a car object that has a owner that has a name. I want to display the car brand and the car‘s owner‘s name together. How do I do this in one query?

eg:

class Seat < ActiveRecord::Base
  belongs_to :car

  def description
    "I am in a #{car.brand} belonging to #{car.owner.name}"
    # --> how do I replace this with one query?
  end
end

I’ll note that this is a highly contrived example to simplify my question. I’m doing this thousands of times in a row, hence the need for more efficiency.

Answer 1

Let us say you are trying to query the Seat model, and you want to eager load the car and owner objects, you can use the includes clause.

Seat.includes(:car => :owner).where(:color => :red).each do |seat|
  "I am in a #{seat.car.brand} belonging to #{seat.car.owner.name}"
end