Local gem class is not found in Rails application

Question

I have written a generator which creates the following ruby file and folder:

app/tests/test.rb

in the test.rb file I have a Test class which looks like this:

class Test < MyCustomModule::MyCustomClass::Base
...
end

Now, I want to use its functionality in one of the show.html.erb files creating new instance like this:

Test.new(...).render(...).html_safe

but I am getting the following error:

uninitialized constant MyCustomModule::MyCustomClass::Base

I have use the following answer to link my gem and my rails application. It seems to work as I am able to use the generator, but the gem module and class are not seen in the rails application.

Could anyone tell how to fix this issue?

---

I have try to follow the tips posted here but still nothing changed:

1. Adding config.autoload_paths += Dir["#{config.root}/lib/**/"] in application.rb file
2. I have created my gem structure looking at CarrierWave gem, so the naming should be correct

3. I try to disable config.threadsafe! but it is already disabled since config.cache_classes and config.eager_load are set to false in development

   DEPRECATION WARNING: config.threadsafe! is deprecated. Rails applications behave by default as thread safe in production as long as config.cache_classes and config.eager_load are set to true.

Also, looking at adding-asset-to-your-gems rails documentation, it is said that:

A good example of this is the jquery-rails gem which comes with Rails as the standard JavaScript library gem. This gem contains an engine class which inherits from Rails::Engine. By doing this, Rails is informed that the directory for this gem may contain assets and the app/assets, lib/assets and vendor/assets directories of this engine are added to the search path of Sprockets.

So, I have done this, and put my model class file in assets folder, but the result is the same.

---

The following screenshots demonstrate my real case:

1. The screenshot below displays my gem file structure

   

2. Here you can see how I am loading the gem in my Rails application Gemfile:

   gem 'thumbnail_hover_effect', '0.0.3', github: 'thumbnail_hover_effec/thumbnail_hover_effec', branch: 'master'
   

3. Then I am using the gem generator a ruby file with a cutstom name in app/thumbnails/test.rb folder with the following code:

   class Test < ThumbnailHoverEffect::Image::Base
   ...
   end
   

   and trying to use the Test class gives me uninitialized constant ThumbnailHoverEffect::Image::Base error.

4. Back in the gem files, these are how the thumbnail_hover_effect file looks like

   require 'thumbnail_hover_effect/version'
   require 'thumbnail_hover_effect/engine'
   require 'thumbnail_hover_effect/image'
   
   module ThumbnailHoverEffect
      # Your code goes here...
   end
   

   and hoe the image file looks like:

    module ThumbnailHoverEffect
    #
       class Image
       ...
      end
    end
   

Answer 1

From what you've posted here there is no ThumbnailHoverEffect::Image::Base defined. Rails autoloading conventions (which you should not be depending on a gem btw, more on that later) would be looking for this file in thumbnail_hover_effect/image/base.rb, but the directory structure you printed does not have that. Of course you could define the class in thumbnail_hover_effect/image.rb and it would work, but the abridged snippet you posted does not show that. So where is ThumbnailHoverEffect::Image::Base defined?

If it's in thumbnail_hover_effect/image/base.rb then that would indicate the file is not being loaded. You can sanity check this by putting a puts 'loading this stupid file' at the top of thumbnail_hover_effect/image/base.rb. That will allow you to bisect the problem by seeing whether there is a problem with your definition of the class, or whether the problem is with loading the proper files. Debugging is all about bisecting the problem.