How to get the child factories from a parent factory - ruby-on-rails-3

Question

I am using RSpec and FactoryGirl to test my Ruby-on-Rails-3 application. I am using a hierarchy of factories:
FactoryGirl.define do
factory :local_airport do
... attributes generic to a local airport
factory :heathrow do
name "London Heathrow"
iata "LHR"
end
factory :stansted do
name "Stansted"
iata "STN"
end
... more local airports
end
end
In my RSpec I sometimes want to be able to create all the child factories by specifying the parent factory. Ideally, something like:
describe Flight do
before( :each ) do
# Create the standard airports
FactoryGirl.find( :local_airport ).create_child_factories
end
end
Many thanks in advance.

Answer 1

You can't really tell a factory to build all it's child factories, as being a child factory just means that it inherits the attributes from the parent. But what you could do is add a trait, for example :with_child_factories. Then your factory would look like the following:
FactoryGirl.define do
factory :local_airport do
... attributes generic to a local airport
factory :heathrow do
name "London Heathrow"
iata "LHR"
end
factory :stansted do
name "Stansted"
iata "STN"
end
... more local airports
trait :with_child_factories do
after(:create) do
FactoryGirl.create(:heathrow)
FactoryGirl.create(:stansted)
...
end
end
end
end
Then you could call it in your test with
FactoryGirl.create(:local_airport, :with_child_factories)

Answer 2

Well after a few hours of delving in the FactoryGirl code I have found a solution. Interestingly FactoryGirl only stores a reference to the parent in the factory, and not from parents to children.
In spec/factories/factory_helper.rb:
module FactoryGirl
def self.create_child_factories( parent_factory )
FactoryGirl.factories.each do |f|
parent = f.send( :parent )
if !parent.is_a?(FactoryGirl::NullFactory) && parent.name == parent_factory
child_factory = FactoryGirl.create( f.name )
end
end
end
end
In my RSpec I can now write:
require 'spec_helper'
describe Flight do
before( :each ) do
# Create the standard airports
FactoryGirl.create_child_factories( :local_airport )
end
...
One gotcha I found is that it is best to have a factory hierarchy that is simple (i.e. two levels). I started with a three layer hierarchy and found I was generating 'abstract' factories that only existed as part of the hierarchy. I have simplified the hierarchy to two levels using traits.