Rails 4 - CarrierWave default_url doesn't work with object image

class ImageUploader < CarrierWave::Uploader::Base

  # Include RMagick or MiniMagick support:
  include CarrierWave::RMagick
  # include CarrierWave::MiniMagick

  # Choose what kind of storage to use for this uploader:
  storage :file
  # storage :fog

  # Override the directory where uploaded files will be stored.
  # This is a sensible default for uploaders that are meant to be mounted:
  def store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end

  def default_url
    ActionController::Base.helpers.asset_path("fallback/" + [main, "default.png"].compact.join('_'))
  end

  # Create different versions of your uploaded files:
  version :thumb do
    process :resize_to_fit => [50, 50]
  end

  version :main do
    process :auto_orient
    process :resize_to_fit => [300, 360]
  end

  def auto_orient
    manipulate! do |img|
      img = img.auto_orient
    end
  end
end

      

        
        
        
      

    

I have a default image loaded in app / assets / images / fallback / main / default.png

This default_url corresponds to the standard pipelined resources described by the pearl of the carrier. It doesn't give me an error, but it doesn't show the default image only the broken image on screen. However, if there is a valid load, it shows the load correctly, so I know the thumb and core processes are running. The only part that breaks is default_url and I have no idea why. I am using rails 4 by the way. Any thoughts / ideas?

Thank!

My code in the view showing the image if loaded and the default broken url is

<div class="img-container">
  <%= image_tag @user.image_url(:main).to_s %>
</div>