gistfile1.rb

class JsonCoder
  # Called to deserialize data to ruby object.
  def load(data)
    d = Oj.load(data || '{}')
    d.recursive_symbolize_keys
  end

  # Called to convert from ruby object to serialized data.
  def dump(obj)
    obj.kind_of?(String) ? obj : Oj.dump(obj, mode: :compat)
  end
end

class Car < ActiveRecord::Base
  serialize :options, JsonCoder.new
end