meeting.rb

class Meeting < ActiveRecord::Base
  serialize :metadata, MeetingMetadata::Coder
end

meeting_metadata.rb

class MeetingMetadata
  include Virtus

  attribute :name, String
  attribute :age, Integer
  attribute :birthday, DateTime

  module Coder
    def self.load(string_value)
      MeetingMetadata.new(JSON.parse(string_value || "{}"))
    end
    def self.dump(meeting_metadata)
      meeting_metadata.to_json
    end
  end
end