Question

I have an after_destroy model callback that regenerates cache after the model instance has been destroyed. It does this by calling open("http://domain.com/page-to-cache") for as many pages as need to be re-cached.

The problem is that the model instance apparently isn’t fully destroyed yet at this time, because those open url requests still register its presence, and the regenerated cache looks exactly like the pre-destroy cache. How can I run those calls after the model instance has been actually destroyed?

Answer 1

You may be able to use an after_commit callback to do something after the entire transaction has gone through to the database. This is different depending on the version of Rails you’re using (2.3.x versus 3.x.x), but is essentially something like the following:

# model_observer.rb
class ModelObserver < ActiveRecord::Observer
  def after_commit(instance)
    do_something if instance.destroyed?
  end
end

You can read some documentation about the Rails 3 after_commit callback here. If your version of Rails doesn’t have an after_commit hook, you can try using this gem which will provide the functionality.