ActiveRecord::Observer, update_all and has_many

Hi,

I'm using an ActiveRecord::Observer to log users changing data in my application. However, I've noted that adding an item to a has_many relationship gets logged, but removing the item does not. That is:

  @product.users << user

is logged, but:

  @product.users.delete(user)

is not.

I've dug into ActiveRecord and found that the underlying issue is that the HasManyAssociation delete_records method uses update_all to update the record. update_all bypasses the normal call backs and therefore also bypasses the Observer.

Is there a way to get an Observer to observe update_all calls?

I've worked out a solution. It might not be the neatest, but it works for me:

has_many has its own call backs. So I can trigger a logging activity using the 'after_remove' call back like this:

  has_many :users, :after_remove => :log_removal

I am then able to grab the Observe object using ObjectSpace:

  def get_an_active_activity_logger     active_loggers = Array.new     ObjectSpace.each_object(ActivityLogger){|l| active_loggers << l}     @activity_logger = active_loggers.first   end

And call one of @activity_logger's public methods to generate the log.

  def log_removal(item)     get_an_active_activity_logger     @activity_logger.log_activity(       self,       'item_removal',       "#{item.class.name} #{item.id} removed from association"     )   end

It means I have to update each of my has_many calls and make the log_removal and get_an_active_activity_logger methods available to the models where they are needed, but both of those are fairly trivial tasks.