Question

I have a model with a has_one association through another model.

class Publisher
  has_many :books
end

class Book
  belongs_to :publisher
  has_one :author
end

class Author
  belongs_to :book
  has_one :publisher, :through => :book
end

In my Rails code, I can call author.publisher without a problem, so that all works nicely. However in my specs (using Rspec and FactoryGirl, the association just doesn’t seem to work. Here are my FactoryGirl definitions:

Factory.define :author do |a|
  a.association :book
end

Factory.define :book do |b|
  b.association :publisher
end

Factory.define :publisher
end

(Omitted most of the attributes from the factories).

Now in my specs, I can do the following

pub = Factory(:publisher)
book = Factory(:book, :publisher => pub)
author = Factory(:author, :book => book)

author.book # => Returns book
author.book.publisher # => Returns publisher 
author.publisher # => nil

So why doesn’t my through association work?

Answer 1

In factory_girl/factory_girl_rails 4.1.0, the following works for me:

factories.rb

FactoryGirl.define do

  factory :author do
    book
  end

  factory :book do
    publisher
  end

  factory :publisher do
  end

end

In the rails console:

pub = FactoryGirl.create(:publisher)
#=> #<Publisher id: 1, created_at: "2013-01-30 13:35:26", updated_at: "2013-01-30 13:35:26">
book = FactoryGirl.create(:book, :publisher => pub)
#=> #<Book id: 1, publisher_id: 1, created_at: "2013-01-30 13:36:23", updated_at: "2013-01-30 13:36:23">
author = FactoryGirl.create(:author, :book => book)
#=> #<Author id: 1, book_id: 1, created_at: "2013-01-30 13:36:57", updated_at: "2013-01-30 13:36:57">
author.book
#=> #<Book id: 1, publisher_id: 1, created_at: "2013-01-30 13:36:23", updated_at: "2013-01-30 13:36:23">
author.book.publisher
#=> #<Publisher id: 1, created_at: "2013-01-30 13:35:26", updated_at: "2013-01-30 13:35:26">
author.publisher
#=> #<Publisher id: 1, created_at: "2013-01-30 13:35:26", updated_at: "2013-01-30 13:35:26">

Curiously, the last author.publisher requires an additional SELECT operation, whereas author.book.publisher does not (perhaps related to the nil you observe):

Publisher Load (0.2ms)  SELECT "publishers".* FROM "publishers"
  INNER JOIN "books" ON "publishers"."id" = "books"."publisher_id"
  WHERE "books"."id" = 1 LIMIT 1

The same thing happens if you use Publisher.create, Book.create, Author.create instead of FactoryGirl.create, so this is not factory girl behaviour but rails behaviour, something to do with how through associations are cached.