partially implemented dirty checking

lib/toy/dirty.rb

@@ -1,5 +1,27 @@
 module Toy
   module Dirty
-
+    extend ActiveSupport::Concern
+    include ActiveModel::Dirty
+
+    module InstanceMethods
+      def attributes_changed!(attributes)
+        attributes.each do |attr_name|
+          attribute_will_change!(attr_name)
+        end
+      end
+
+      def save
+        super.tap { changed_attributes.clear }
+      end
+
+      def write_attribute(name, value)
+        name = name.to_s
+        unless attribute_changed?(name)
+          old = read_attribute(name)
+          changed_attributes[name] = old if old != value
+        end
+        super
+      end
+    end    
   end
 end

lib/toy/store.rb

@@ -7,6 +7,7 @@ module Store
       include ActiveModel::Conversion
       include Attributes
       include Persistence
+      include Dirty
       include Querying
 
       include Callbacks

spec/toy/dirty_spec.rb

@@ -3,20 +3,20 @@
 describe Toy::Dirty do
   before :each do
     model = Model('Foo') do
-      store FileStore
-      attribute :name
+      store RedisStore
+      attribute :name, String
     end
     @foo = model.create(:name => 'Geoffrey')
   end
   let(:foo) { @foo }
 
-  xit "should identify when there are no changes" do
+  it "should identify when there are no changes" do
     foo.changed?.should be_false
     foo.changed.should be_empty
     foo.changes.should be_empty
   end
 
-  xit "should identify when there are changes" do
+  it "should identify when there are changes" do
     foo.name = 'John'
 
     foo.changed?.should be_true