Rails force models to eager load

Question

I would like to be able to load an entire app so that I may find the descendants of a given class.

For example given I have the following class defined:

Answer 1

After a great deal of trial and error, I recently learned that Jason Waldrip's answer is somewhat incomplete. As of Rails 5, Rails.application.eager_load! will indeed load all of the directories specified in config/application.rb. But it doesn't match Rails' actual behavior in production. To do that, one must instead mirror what Rails does:

Rails.configuration.eager_load_namespaces.each(&:eager_load!)

The salient difference between the approaches is that OPs answer won't eager load the files within app directories of Engines that live in the gems or vendor folders. Whereas Rails itself will identify where subclasses of Engine exist and will see to it that the appropriate app subdirectories are eager-loaded.

Behind the scenes

Rails 5 adds eager load directories in railties-5.0.2/lib/rails/engine/configuration.rb:39, where it runs

      paths.add "app",                 eager_load: true, glob: "{*,*/concerns}"
      paths.add "app/assets",          glob: "*"
      paths.add "app/controllers",     eager_load: true
      paths.add "app/channels",        eager_load: true, glob: "**/*_channel.rb"
      paths.add "app/helpers",         eager_load: true
      paths.add "app/models",          eager_load: true
      paths.add "app/mailers",         eager_load: true

These directories are not currently included in a default Rails.application.eager_load!