Populating an association with children in factory_girl

Question

I have a model Foo that has_many 'Bar'. I have a factory_girl factory for each of these objects. The factory for Bar has an association to Foo; it will instantiate a Foo when it creates the Bar.

I'd like a Factory that creates a Foo that contains a Bar. Ideally this Bar would be created through the :bar factory, and respect the build strategy (create/build) used to create the Foo.

I know I could just call the :bar factory and then grab the Foo reference from the new Bar. I'd like to avoid this; in my test case, the important object is Foo; calling the Bar factory seems a bit circuitous. Also, I can see the need for a Foo with multiple Bars.

Is this possible in factory_girl? How do you define this relationship in the parent?

Elsi

Answer 1

The Factory.after_ hooks appear to be the only way to do this successfully. I've figured out a way to maintain the build strategy without duplicating code:

Factory.define :foo do |f|
  f.name "A Foo"
  f.after(:build) { |foo|
    foo.bars << Factory.build(:bar, :foo => foo)
  }
  f.after(:create) { |foo|
    foo.bars.each { |bar| bar.save! }
  }
end

The documentation states that after_build will be called before after_create if the :create build strategy is used. If :build is used, then only after_build is called, and everyone is happy.

I've also created an abstracted generally-applicable version at this gist to keep things DRY.

Elsi

It is hard to believe that this is the best way to do this but It still seems to be the case. Up-voted this answer. – Voracity

How do you use your gist version? What's the best way to incorporate that into a Rails app? – Inquiline

As noted here, using << to add an association persists the changes. To avoid that, the after(:build) should be foo.association(:bars).add_to_target(Factory.build(:bar, :foo => foo) ) – Plexor

Answer 2

You can use the association method both ways:

Factory.define :foo do |f|
  # ...
  f.association :bar
end

If that won't work, you can associate them manually using a callback. Here's an example from one of my apps:

Factory.define :live_raid do |raid|
end

Factory.define :live_raid_with_attendee, :parent => :live_raid do |raid|
  raid.after_create { |r| Factory(:live_attendee, :live_raid => r) }
end

Rid

The first syntax causes a a stack overflow/infinite recursion in my code. The second syntax works wonderfully, except that it doesn't obey the build strategy. – Elsi

Answer 3

FactoryGirl now has a :method => :build option you can use on the association, which will build the associated object rather than creating it.

#64: Building an object creates associations

Humfrid

Answer 4

FactoryGirl 4.3.0 is calling save! on an association when calling build on the parent object, which i believe is not intended to be the correct behavior.

After digging through the FactoryGirl code, adding strategy: :build to the association definition in the factory seems now be creating my association without calling save!.

Kraft

Answer 5

Using factory_girl-4.5.0, create n child objects in a parent object factory

FactoryGirl.define do
  factory :foo do
    name "test"        

    after(:build) do |instance|
      n.times { instance.bars << FactoryGirl.create(:bar) }          
    end
  end
end

Auklet