openfoodnetwork/lib/open_food_network/paperclippable.rb

# Allow use of Paperclip's has_attached_file on non-ActiveRecord classes
# https://gist.github.com/basgys/5712426

module OpenFoodNetwork
  module Paperclippable
    def self.included(base)
      base.send :extend, ActiveModel::Naming
      base.send :extend, ActiveModel::Callbacks
      base.send :include, ActiveModel::Validations
      base.send :include, Paperclip::Glue

      # Paperclip required callbacks
      base.send :define_model_callbacks, :save, only: [:after]
      base.send :define_model_callbacks, :commit, only: [:after]
      base.send :define_model_callbacks, :destroy, only: [:before, :after]

      # Initialise an ID
      base.send :attr_accessor, :id
      base.instance_variable_set :@id, 1
    end

    # ActiveModel requirements
    def to_model
      self
    end

    def valid?()      true end
    def new_record?() true end
    def destroyed?()  true end

    def save
      run_callbacks :save do
      end
      true
    end

    def errors
      obj = Object.new
      def obj.[](key)         [] end
      def obj.full_messages() [] end
      def obj.any?()       false end
      obj
    end
  end
end