FactoryGirl: Passing attributes to associated records using transient attributes

associated_records_in_factory_girl.rb

FactoryGirl.define do

  factory :parent do
    transient do
      child_name nil
      child_allowed_to_drive false
    end
    
    child do
      create(:child, name: child_name, allowed_to_drive: child_allowed_to_drive)
    end
  end

  factory :child do
    name 'Child'
    allowed_to_drive false
  end

end

# Usage
daughter = FactoryGirl.create(:parent, child_name: 'Lisa').child
daughter.name # => 'Lisa'
daughter.allowed_to_drive? # => false

son = FactoryGirl.create(:parent, child_name: 'Benedikt', child_allowed_to_drive: true).child
son.name # => 'Benedikt'
son.allowed_to_drive? # => false