monkey patch for carrierwave to make updates remove previous images when activerecord's identity map is enabled

image.rb

# -*- encoding : utf-8 -*-
class Image < ActiveRecord::Base

  mount_uploader :image, ImageUploader

  private

  #############################################################################
  # CarrierWave's behavior as of 0.5.8 is not compatible with ActiveRecord's
  # identity map. This is a monkey patch.
  def store_previous_model_for_image
    if image.remove_previously_stored_files_after_update && image_changed?
      @remove_previous_image = true
    end
  end

  def remove_previously_stored_image
    if @remove_previous_image
      ImageUploader.new(self, :image).tap do |uploader|
        uploader.retrieve_from_store!(image_was.file.original_filename)
        uploader.remove!
      end
      @remove_previous_image = nil
    end
  end
  #############################################################################
end