Manual Versioning for Mongoid 2.0

mongoid_manual_versioning.rb

module Mongoid #:nodoc:
  # Include this module to get manual versioning of root level documents.
  # This will add a version field to the +Document+ and a has_many association
  # with all the versions contained in it.
  # Unlike Mongoid::Versioning, you must manually increment the version field
  # when you want to bump versions
  module Versioning
    module Manual
      extend ActiveSupport::Concern
      include Mongoid::Versioning

      # Create a new version of the +Document+. This will load the previous
      # document from the database and set it as the next version before saving
      # the current document. It then increments the version number. If a #max_versions
      # limit is set in the model and it's exceeded, the oldest version gets discarded.
      def revise
        if @modifications.has_key?('version')
          last_version = self.class.first(:conditions => { :_id => id, :version => @modifications['version'][0] })
          if last_version
            versions.target << last_version.clone
            versions.shift if version_max.present? && versions.length > version_max
            @modifications['versions'] = [ nil, versions.as_document ] if @modifications
          end
        end
      end
    end
  end
end