Make serialized columns with explicit object_type return a new instance of the...

Make serialized columns with explicit object_type return a new instance of the object instead of nil

activerecord/lib/active_record/base.rb

@@ -249,6 +249,17 @@ module ActiveRecord #:nodoc:
   #   user = User.create(:preferences => %w( one two three ))
   #   User.find(user.id).preferences    # raises SerializationTypeMismatch
   #
+  # When you specify a class option, the default value for that attribute will be a new
+  # instance of that class.
+  #
+  #   class User < ActiveRecord::Base
+  #     serialize :preferences, OpenStruct
+  #   end
+  #
+  #   user = User.new
+  #   user.preferences.theme_color = "red"
+  #
+  #
   # == Single table inheritance
   #
   # Active Record allows inheritance by storing the name of the class in a column that by
@@ -1409,6 +1420,7 @@ def initialize(attributes = nil)
         @changed_attributes = {}
 
         ensure_proper_type
+        set_serialized_attributes
 
         populate_with_current_scope_attributes
         self.attributes = attributes unless attributes.nil?
@@ -1447,10 +1459,7 @@ def encode_with(coder)
       def init_with(coder)
         @attributes = coder['attributes']
 
-        (@attributes.keys & self.class.serialized_attributes.keys).each do |key|
-          coder = self.class.serialized_attributes[key]
-          @attributes[key] = coder.load @attributes[key]
-        end
+        set_serialized_attributes
 
         @attributes_cache, @previously_changed, @changed_attributes = {}, {}, {}
         @association_cache = {}
@@ -1461,6 +1470,13 @@ def init_with(coder)
         run_callbacks :initialize
       end
 
+      def set_serialized_attributes
+        (@attributes.keys & self.class.serialized_attributes.keys).each do |key|
+          coder = self.class.serialized_attributes[key]
+          @attributes[key] = coder.load @attributes[key]
+        end
+      end
+
       # Specifies how the record is dumped by +Marshal+.
       #
       # +_dump+ emits a marshalled hash which has been passed to +encode_with+. Override this

activerecord/lib/active_record/coders/yaml_column.rb

@@ -19,6 +19,7 @@ def dump(obj)
       end
 
       def load(yaml)
+        return object_class.new if object_class != Object && yaml.nil?
         return yaml unless yaml.is_a?(String) && yaml =~ /^---/
         begin
           obj = YAML.load(yaml)
@@ -27,6 +28,7 @@ def load(yaml)
             raise SerializationTypeMismatch,
               "Attribute was supposed to be a #{object_class}, but was a #{obj.class}"
           end
+          obj ||= object_class.new if object_class != Object
 
           obj
         rescue *RESCUE_ERRORS

activerecord/test/cases/base_test.rb

@@ -1002,6 +1002,25 @@ def test_serialized_attribute_with_class_constraint
     Topic.serialize(:content)
   end
 
+  def test_serialized_default_class
+    Topic.serialize(:content, Hash)
+    topic = Topic.new
+    assert_equal Hash, topic.content.class
+    assert_equal Hash, topic.read_attribute(:content).class
+    topic.content["beer"] = "MadridRb"
+    assert topic.save
+    topic.reload
+    assert_equal Hash, topic.content.class
+    assert_equal "MadridRb", topic.content["beer"]
+  ensure
+    Topic.serialize(:content)
+  end
+
+  def test_serialized_no_default_class_for_object
+    topic = Topic.new
+    assert_nil topic.content
+  end
+
   def test_serialized_boolean_value_true
     Topic.serialize(:content)
     topic = Topic.new(:content => true)

activerecord/test/cases/coders/yaml_column_test.rb

+
 require "cases/helper"
 
 module ActiveRecord
@@ -20,9 +21,9 @@ def test_nil_is_ok
         assert_nil coder.load "--- "
       end
 
-      def test_nil_is_ok_with_different_class
+      def test_returns_new_with_different_class
         coder = YAMLColumn.new SerializationTypeMismatch
-        assert_nil coder.load "--- "
+        assert_equal SerializationTypeMismatch, coder.load("--- ").class
       end
 
       def test_returns_string_unless_starts_with_dash