include ActiveModel::StateMachine imports classes defined in ActiveModel::StateMachine module

I have a model called Event defined.


class Booking < ActiveRecord::Base
belongs_to :event end

class Event < ActiveRecord::Base
end

When i add include ActiveModel::StateMachine to my Booking model the association stops working.

Booking.last.event NameError: undefined local variable or method event' for #<Class:0x7f68edac8728><br/>

from #{RAILS_ROOT}/vendor/rails/activerecord/lib/active_record/base.rb:1959:in `method_missing'
from #{RAILS_ROOT}/vendor/rails/activerecord/lib/active_record/base.rb:2199:in `compute_type'
from #{RAILS_ROOT}/vendor/rails/activesupport/lib/active_support/core_ext/kernel/reporting.rb:11:in `silence_warnings'
from #{RAILS_ROOT}/vendor/rails/activerecord/lib/active_record/base.rb:2195:in `compute_type'
from #{RAILS_ROOT}/vendor/rails/activerecord/lib/active_record/reflection.rb:156:in `send'
from #{RAILS_ROOT}/vendor/rails/activerecord/lib/active_record/reflection.rb:156:in `klass'
from #{RAILS_ROOT}/vendor/rails/activerecord/lib/active_record/associations/belongs_to_association.rb:49:in `find_target'
from #{RAILS_ROOT}/vendor/rails/activerecord/lib/active_record/associations/association_proxy.rb:240:in `load_target'
from #{RAILS_ROOT}/vendor/rails/activerecord/lib/active_record/associations/association_proxy.rb:112:in `reload'
from #{RAILS_ROOT}/vendor/rails/activerecord/lib/active_record/associations.rb:1247:in `event'
from (irb):2

I tracked the problem to ActiveModel::StateMachine::Event being imported as can be seen from this code:

Booking.reflections[:event] => #<ActiveRecord::Reflection::AssociationReflection:0x7fa1123db200 @klass=ActiveModel::StateMachine::Event, @primary_key_name="event_id", @active_record=Booking(id: integer, event_id: integer), @options={}, @macro=:belongs_to, @class_name="Event", @name=:event>

So .find is being called on ActiveModel::StateMachine::Event.

If i instead use:

require 'active_model/state_machine/machine' extend ActiveModel::StateMachine::ClassMethods

Then the behaviour is correct.


?> Booking.reflections[:event] => #<ActiveRecord::Reflection::AssociationReflection:0x7f3505b2a840 @klass=Event(id: integer, name: string), @primary_key_name="event_id", @active_record=Booking(id: integer, event_id: integer), @options={:class_name=>"Event"}, @macro=:belongs_to, @class_name="Event", @name=:event>

This is very different from the expected behaviour where the Event constant is not redefined and association works as normal.