What does has_many_polymorphs mean by "Referential integrity violation"?

Question

I have a has_many_polymorphs relationship between a Candidate and many events of various type. In particular, a Candidate creates a Created event when it is created.

class Candidate < ActiveRecord::Base
  has_many_polymorphs :events, :through => :candidate_events,
                               :from => Event::Base.included_in_classes.map { |klass|
                                 klass.to_s.underscore.pluralize.to_sym
                               })
  after_validation_on_create :create_created_event

  private
  def create_creation_event
    Event::Created.create!(:candidate => self, :creator => creator)
  end
end

class CandidateEvent < ActiveRecord::Base
  belongs_to :candidate
  belongs_to :event, :polymorphic => true
end

module Event::Base
  ...
end

class Event::Created < ActiveRecord::Base
  include Event::Base
  validates_presence_of :creator
end

When I run my unit tests, everything is fine. When I run my functional tests, everything is fine. When I run my integration (Cucumber) tests, everything is fine. When I run in production, everything is fine. When I try to run in development mode (with class-reloading on), I get

Referential integrity violation; child <Event::Created:1> was not found for :events.
Expected record['candidate_events.event_id'] (1) to be equal to record['created_events.id'] ().
  {
    "candidate_events.event_type"=>"Event::Created",
    "candidate_events.created_at"=>"2009-08-05 20:28:31",
    "candidate_events.updated_at"=>"2009-08-05 20:28:31",
    "candidate_events.candidate_id"=>"1",
    "candidate_events.event_id"=>"1",
    "candidate_events.id"=>"1"
  }

Running script/console in the same (development) environment I see that Event::Created object with the proper relationship to the CandidateEvent cross-reference model.

What's going on?

Answer 1

Can we be sure that Event::Base.included_in_classes is returning the right classes when classes reload? Isn't this trick sort of load order dependent? ie perhaps Event::Created hasn't yet included Event::Base?