model_files.rb

class ModelFile < ActiveRecord::Base

  has_attached_file :file,
    :url => "/model_files/:id/download",
    :path => ":rails_root/secure_files/:class/:id_and_version/:style/:basename.:extension",
    :keep_old_files => true  # save old versions around..
                                                            

  # This returns the actual path of the file for the current_version of this file
  def versioned_file_path(from_version = nil)
    current_version = version
    # we need to set the @version because the file.path will use that version in the path interpolation
    @version = version_for_file_path(from_version)
    file_path = file.path
    # reset it back to the current version because we want to keep the version alone
    @version = current_version
    file_path
  end
  
  
  protected

  # Helper method for versioned_file_path
  # this is useful to find the version of when the file content was actually stored on disk
  # this is needed because if something else changes later, then the version will increase but the file
  # will actually be under and old version.
  def version_for_file_path(from_version = nil, to_version = 1)
    from_version ||= version
    return 1 if versions.empty?
    versions.between(from_version, to_version).each do |past_version|
      return past_version.original_number if past_version.modifications.include?("file_updated_at")
    end

    return 1
  end       

model_files_controller.rb

class ModelFilesController < ActiveRecord::Base
  def download
    @collaboration_file.revert_to(params[:version].to_i) if params[:version].present?
    send_file(@collaboration_file.versioned_file_path, :type => @collaboration_file.file_content_type)
  end
end

Paperclip and VestalVersions

This is a brief description of how to get VestalVersions and Paperclip to play nicely.

The paperclip_initializer.rb extends paperclip for a new option :keep_old_files which means that paperclip won't remove the file when a new file is uploaded.  In order for this to work, the model also needs to have to have specific settings:

  #1.  The version needs to be included in the file path
  #2.  A method to get the actual path to the file. (The file may not be at the current version)

You can view both these settings in the model_files.rb file below.

Note: If you dealing with public files then you will need to include the :id_and_version option in the :url and :path.  Then in the view you need to reference the model_file.versioned_file_path.

paperclip_initializer.rb

Paperclip.interpolates(:id_and_version) { |attachment,style| "#{attachment.instance.id}/#{attachment.instance.version}"  }

module Paperclip
  class Attachment
    # override the save to hack in to keep files around
    def save
      flush_deletes unless @options[:keep_old_files]
      flush_writes
      @dirty = false
      true
    end
  end
  
  # keep files around after destroy
  module InstanceMethods
    def destroy_attached_files
      Paperclip.log("Deleting attachments.")
      each_attachment do |name, attachment|
        attachment.send(:queue_existing_for_delete)
        attachment.send(:flush_deletes) unless attachment.options[:keep_old_files]
      end
    end
  end
  
end