Question

I’ve been trying to figure this out for a while, but what is the best way to find all principals based on their single dependents properties. For example, let’s say I have these models:

class Principal < ActiveRecord::Base
  has_one :dependent
end

class Dependent < ActiveRecord::Base
  belongs_to :principal

  attr_accessible :color
end

How can I query the database to give me back all the Principals whose dependents have the color blue? If the answer isn’t the same, what if I wanted a range (say :color was actually :number, and I wanted all the principals whose dependent’s number fall within the range of 10-20).

Here is the closest solution I have to this problem, I’m sure it’s terribad:

principal_collection = Array.new
Dependent.where(:color => 'blue').each do |d|
  principal_collection << d.principal
end

Thanks in advance 🙂 I apologize if the answer is out there, I tried searching.

Answer 1

Maybe you are finding this?

Principal.includes(:dependent).where("dependents.color = ?", "blue")