Question

Is it possible to make a has_one relationship work like this?

I would like to be able able to load records like this:

@person = Person.find(1) => {Person id: 1, favorite_house_id: 10}
@person.favorite_house => {House id: 10....)

class Person < ActiveRecord::Base
  has_many :houses, through: :person_houses
  has_one :favorite_house, through: :person_houses     
end

class PersonHouse < ActiveRecord::Base
  belongs_to :house
  belongs_to :person
end

class House < ActiveRecord::Base
  has_many :people, through: :person_houses
end

Answer 1

Replace the has_one relation of Person by:

belongs_to :favorite_house, :class_name => "House"

Do not forget to create a column favorite_house_id in the table of Person.