FactoryGirl association model trouble: “SystemStackError: stack level too deep”

Question

I am using Ruby on Rails 3.0.9, RSpec-rails 2 and FactoryGirl. I am trying to state a Factory association model but I am in trouble.

I have a factories/user.rb

Answer 1

According to the docs, you can't just put both sides of the associations into the factories. You'll need to use their after callback to set an object(s) to return.

For instance, in the factories/users/account.rb file, you put something like

after(:build) do |user_account, evaluator|
    user_account.user = FactoryGirl.build(:user, :account=>user_account)
end

For has_many associations, you'll need to use their *_list functions.

after(:build) do |user_account, evaluator|
    user_account.users = FactoryGirl.build_list(:user, 5, :account=>user_account)
end

---

Note: I believe the example in the docs is a bit misleading it doesn't assign anything to the object. I believe it should be something like (note the assignment).

# the after(:create) yields two values; the user instance itself and the
# evaluator, which stores all values from the factory, including ignored
# attributes; `create_list`'s second argument is the number of records
# to create and we make sure the user is associated properly to the post
after(:create) do |user, evaluator|
  user.posts = FactoryGirl.create_list(:post, evaluator.posts_count, user: user)
end

Answer 2

Spyle's excellent answer (still working with Rails 5.2 and RSpec 3.8) will work for most associations. I had a use case where a factory needed to use 2 different factories (or different traits) for a single has_many association (ie. for a scope type method).

What I ended up coming up with was:

# To build user with posts of category == 'Special' and category == 'Regular'
after(:create) do |user, evaluator|
  array = []
  array.push(FactoryBot.create_list(:post, 1, category: 'Regular')
  array.push(FactoryBot.create_list(:post, 1, category: 'Special')
  user.posts = array.flatten
end

This allowed the user to have 1 post of category 'Regular' and 1 post of category 'Special.'