How do I hook into Rails *after* files are reloaded on each request in development mode?

Question

I'm working on a gem that sets properties on ActiveRecord models (such as table_name) dynamically based on a user config option.

I have an initializer that achieves this. My problem however is that in dev mode, these classes are reloaded, so they don't maintain these values set.

So I thought I'd use a railtie to hook into the point where these files are reloaded and run my config again on the models. My problem however is that config.to_prepare in the railtie appears to run before the reload! actually takes place. I can prove this with a bit of logging:

module MyMod
  class Railtie < Rails::Railtie

    config.to_prepare do
      Rails.logger.debug("Contact object_id: #{Contact.object_id}")
    end
  end
end

if I load up my console, I get the first log:

Contact object_id: 2202692040

If I check Contact.object_id it matches up:

Contact.object_id  #=> 2202692040

Then I reload!

reload!

Rails logger from my to_prepare logs:

Contact object_id: 2202692040

So it still has the old object_id, but when I check it in the console:

Contact.object_id  #=> 2197355080

Which is the newly loaded class object id.

So how do I get to_prepare to run after the files are reloaded? Using Rails 3.0.10

update

I've also tried manually attaching this action to the after_prepare callback on the ActionDispatch::Callbacks like so:

initializer "apartment.init" do
  ActionDispatch::Callbacks.set_callback(:prepare, :after) do
    Rails.logger.debug("Contact object_id: #{Contact.object_id}")
  end
end

It does indeed run the callback after the config.to_prepare but it still appears to happen before the files are reloaded... I get the same behaviour as above.

Answer 1

Write an initializer that, if cache_classes is false, uses ActionDispatch::Reloader to set a to_prepare callback that runs your gem's installation routine.

initializer 'foobar.install' do
  if Rails.configuration.cache_classes
    FooBar.install!
  else
    ActionDispatch::Reloader.to_prepare do
      FooBar.install!
    end
  end
end

It'll work both in the console with the reload! method and in the Rack application server.