engine/app/models/locomotive/extensions/content_type/item_template.rb

module Locomotive
  module Extensions
    module ContentType
      module ItemTemplate

        extend ActiveSupport::Concern

        included do
          field :raw_item_template
          field :serialized_item_template, :type => Binary

          before_validation :serialize_item_template

          validate :item_template_must_be_valid
        end

        module InstanceMethods

          def item_template
            @item_template ||= Marshal.load(read_attribute(:serialized_item_template).to_s) rescue nil
          end

          protected

          def serialize_item_template
            if self.new_record? || self.raw_item_template_changed?
              @item_parsing_errors = []

              begin
                self._parse_and_serialize_item_template
              rescue ::Liquid::SyntaxError => error
                @item_parsing_errors << I18n.t(:liquid_syntax, :error => error.to_s, :scope => [:errors, :messages])
              end
            end
          end

          def _parse_and_serialize_item_template
            item_template = ::Liquid::Template.parse(self.raw_item_template, {})
            self.serialized_item_template = BSON::Binary.new(Marshal.dump(item_template))
          end

          def item_template_must_be_valid
            @item_parsing_errors.try(:each) do |msg|
              %w(item_template raw_item_template).each { |field| self.errors.add field.to_sym, msg }
            end
          end

        end

      end
    end
  end
end