How to auto-reload changes in a Rails Engine?

Question

I have a Rails 4.1.0 mountable engine. In the engine's application_helper.rb:

module MyEngine
  module ApplicationHelper    
    def test123
      "test123"
    end    
  end
end

The method is in the dummy app's view general/index.html.erb view:

%<= test123 %>

This works. However, when I change the string returned by def test123 and refresh the browser, the new string is not displayed.

Of course, restarting the web server in the dummy app shows the new string.

So the question is, how to reload the engine's files without having to restart the web server?

PS. I am preferably looking for a way to do this using Rails itself, or a specific gem that solves this problem (but not the generic gems like Guard, Spork etc. although if all else fails, I will consider those too.)

PPS. There are similar questions on SO, but I have tried them all (even though they are for Rails 2.x, 3.x), and they have not worked for me.

Answer 1

You should explicitly require dependent helpers:

# engines/my_engine/app/controllers/my_engine/application_controller.rb

require_dependency "my_engine/application_helper"  # This is a key point!

module MyEngine
  class ApplicationController < ::ApplicationController
    helper ApplicationHelper
    ...