1 files changed, 89 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/attribute_methods/serialization.rb b/activerecord/lib/active_record/attribute_methods/serialization.rb
new file mode 100644
index 0000000000..0a4432506f
--- /dev/null
+++ b/activerecord/lib/active_record/attribute_methods/serialization.rb
@@ -0,0 +1,89 @@
+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