FileUpdateChecker specifies the API used by Rails to watch files and control reloading. The API depends on four methods:

• initialize which expects two parameters and one block as described below.

• updated? which returns a boolean if there were updates in the filesystem or not.

• execute which executes the given block on initialization and updates the latest watched files and timestamp.

• execute_if_updated which just executes the block if it was updated.

After initialization, a call to execute_if_updated must execute the block only if there was really a change in the filesystem.

This class is used by Rails to reload the I18n framework whenever they are changed upon a new request.

i18n_reloader = ActiveSupport::FileUpdateChecker.new(paths) do
  I18n.reload!
end

ActionDispatch::Reloader.to_prepare do
  i18n_reloader.execute_if_updated
end