Reprocess all attachments from all models of the app and engines

paperclip_global_reprocessor.rb

class PaperclipGlobalReprocessor
  def run
    models.each do |model| 
      attachments = model.try(:attachment_definitions).try(:keys)

      next unless attachments

      model.find_each do |resource| 
        attachments.each do |attachment| 
          resource.send(attachment).reprocess! if resource.send(:"#{ attachment }?") 
        end
      end
    end
  end
  
  private

  # Get all engines to ensure that we lookup all standard places where models
  # can live
  def engines
    [Rails.application] + Rails::Engine.subclasses.map(&:instance)
  end
  
  # Find all "app/models" folder in the engines and fetch all model files.
  def models
    engines.flat_map do |app|
      (app.paths['app/models'].to_a + app.config.autoload_paths).map do |load_path|
        Dir.glob(app.root.join(load_path)).map do |load_dir|
          Dir.glob(load_dir + '/**/*.rb').map do |filename|
            next unless filename.match(/\/models\//)
            # app/models/module/class.rb => module/class.rb
            model_name = filename.to_s.reverse.chomp("#{app.root.join(load_dir)}/".reverse).reverse
            # module/class.rb => module/class => Module::Class
            begin
              model_name.chomp('.rb').camelize.constantize
            rescue NameError, LoadError
              nil
            end
          end
        end
      end
    end.flatten.compact.uniq
  end
end

PaperclipGlobalReprocessor.new.run