module ActiveRecord module AttributeMethods module Serialization extend ActiveSupport::Concern 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 assignment and retrieval. # Otherwise SerializationTypeMismatch will be raised. # # Empty objects as {}, in the case of +Hash+, or [], in the case of # +Array+, will always be persisted as null. # # Keep in mind that database adapters handle certain serialization tasks # for you. For instance: +json+ and +jsonb+ types in PostgreSQL will be # converted between JSON object/array syntax and Ruby +Hash+ or +Array+ # objects transparently. There is no need to use #serialize in this # case. # # For more complex cases, such as conversion to or from your application # domain objects, consider using the ActiveRecord::Attributes API. # # ==== Parameters # # * +attr_name+ - The field name that should be serialized. # * +class_name_or_coder+ - Optional, a coder object, which responds to +.load+ and +.dump+ # or a class name that the object type should be equal to. # # ==== Example # # # Serialize a preferences attribute. # class User < ActiveRecord::Base # serialize :preferences # end # # # Serialize preferences using JSON as coder. # class User < ActiveRecord::Base # serialize :preferences, JSON # end # # # Serialize preferences as Hash using YAML coder. # class User < ActiveRecord::Base # serialize :preferences, Hash # end def serialize(attr_name, class_name_or_coder = Object) # When ::JSON is used, force it to go through the Active Support JSON encoder # to ensure special objects (e.g. Active Record models) are dumped correctly # using the #as_json hook. coder = if class_name_or_coder == ::JSON Coders::JSON elsif [:load, :dump].all? { |x| class_name_or_coder.respond_to?(x) } class_name_or_coder else Coders::YAMLColumn.new(attr_name, class_name_or_coder) end decorate_attribute_type(attr_name, :serialize) do |type| Type::Serialized.new(type, coder) end end end end end end