Adding Callbacks to a Rails Concern (BackgroundDestroyable)

background_destroyable.rb

# BackgroundDestroyable classes MUST have deleted_at:datetime column
# BackgroundDestroyable enable :background_destroy and :background_restore callbacks
module BackgroundDestroyable
  extend ActiveSupport::Concern
  include ActiveModel::Callbacks

  included do
    define_model_callbacks :background_destroy, :background_restore

    default_scope { where(deleted_at: nil) }
    scope :deleted, -> { unscoped.where.not(deleted_at: nil) }
  end

  def destroy(mode = :background)
    if mode == :background
      unless self.deleted_at.present?
        run_callbacks :background_destroy do
          update_attribute :deleted_at, Time.now
          Resque.enqueue(BackgroundDestroyer, self.id, self.class.to_s)
        end
      end
    elsif mode == :now
      self.class.uploaders.each do |uploader, uploader_class|
        self.send("remove_#{uploader}!")
      end
      super()
    end
  end

  def destroy_now!
    self.destroy(:now) if self.deleted_at
  end

  def restore
    run_callbacks :background_restore do
      update_attribute :deleted_at, nil
    end
  end
end

pose.rb

class Pose < ActiveRecord::Base
  include BackgroundDestroyable
  belongs_to :photo
  validates_presence_of :photo, :pose

  before_background_destroy :decrement_multilevel_counter
  before_background_restore :increment_multilevel_counter

  private
  def increment_multilevel_counter
    photo.parent.class.increment_counter(:poses_count, photo.parent.id)
  end

  def decrement_multilevel_counter
    photo.parent.class.decrement_counter(:poses_count, photo.parent.id)
  end
end