module ActiveRecord module AttributeMethods module Serialization extend ActiveSupport::Concern included do # Returns a hash of all the attributes that have been specified for serialization as # keys and their class restriction as values. class_attribute :serialized_attributes self.serialized_attributes = {} end class Attribute < Struct.new(:coder, :value, :state) def unserialized_value state == :serialized ? unserialize : value end def serialized_value state == :unserialized ? serialize : value end def unserialize self.state = :unserialized self.value = coder.load(value) end def serialize self.state = :serialized self.value = coder.dump(value) end end module ClassMethods # If you have an attribute that needs to be saved to the database as an object, and retrieved as the same object, # then specify the name of that attribute using this method and it will be handled automatically. # The serialization is done through YAML. If +class_name+ is specified, the serialized object must be of that # class on retrieval or SerializationTypeMismatch will be raised. # # ==== Parameters # # * +attr_name+ - The field name that should be serialized. # * +class_name+ - Optional, class name that the object type should be equal to. # # ==== Example # # Serialize a preferences attribute # class User < ActiveRecord::Base # serialize :preferences # end def serialize(attr_name, class_name = Object) coder = if [:load, :dump].all? { |x| class_name.respond_to?(x) } class_name else Coders::YAMLColumn.new(class_name) end # merge new serialized attribute and create new hash to ensure that each class in inheritance hierarchy # has its own hash of own serialized attributes self.serialized_attributes = serialized_attributes.merge(attr_name.to_s => coder) end private def attribute_cast_code(attr_name) if serialized_attributes.include?(attr_name) "v.unserialized_value" else super end end end def set_serialized_attributes self.class.serialized_attributes.each do |key, coder| if @attributes.key?(key) @attributes[key] = Attribute.new(coder, @attributes[key], :serialized) end end end def type_cast_attribute_for_write(column, value) if column && coder = self.class.serialized_attributes[column.name] Attribute.new(coder, value, :unserialized) else super end end end end end