Damselfly is a Rails engine to add polymorphic file attachments leveraging dragonfly and counting references to avoid duplicates.

Your rails application should be using Dragonfly. If it's not, then follow its instructions to install and configure it, then come back here. Add Damselfly to your Gemfile:

gem 'damselfly'

Grab one of your models and include the Damselfly module, then declare any attachments you need:

class Person < ActiveRecord::Base
  include Damselfly
  has_one_attached :avatar
  has_many_attached :photos
end

Internally, Damselfly treats singular attachments like a has_one association, and plural ones as a has_many. Just assign the data attribute to your attachment_attributes, like so:

@john = Person.create!(name: "John", avatar_attributes: {data: Rails.root.join('sample.jpg')}, photos_attributes: [{data: Rails.root.join('another_sample.jpg')}])

That's all. You can now access @john.avatar or @john.photos as you would do with a model that uses dragonfly.

This project rocks and uses MIT-LICENSE.