Merge branch '0.9'

* 0.9:
  Simply dirty tracking by comparing casted values before and after the change
  Avoid casting blank strings to floats
  added test: changed? should be false if the same ObjectId was assigned in String format

lib/mongo_mapper/extensions/float.rb

@@ -3,7 +3,7 @@ module MongoMapper
   module Extensions
     module Float
       def to_mongo(value)
-        value.nil? ? nil : value.to_f
+        value.blank? ? nil : value.to_f
       end
     end
   end

lib/mongo_mapper/plugins/dirty.rb

@@ -47,19 +47,14 @@ def clear_changes
 
         def write_key(key, value)
           key = key.to_s
-          old = read_key(key)
-          attribute_will_change!(key) if attribute_should_change?(key, old, value)
-          changed_attributes.delete(key) unless attribute_value_changed?(key, attribute_was(key), value)
-          super(key, value)
-        end
-
-        def attribute_should_change?(key, old, value)
-          attribute_changed?(key) == false && attribute_value_changed?(key, old, value)
+          attribute_will_change!(key) unless attribute_changed?(key)
+          super(key, value).tap do
+            changed_attributes.delete(key) unless attribute_value_changed?(key)
+          end
         end
 
-        def attribute_value_changed?(key_name, old, value)
-          value = nil if keys[key_name.to_s].number? && value.blank?
-          old != value
+        def attribute_value_changed?(key_name)
+          attribute_was(key_name) != read_key(key_name)
         end
       end
     end

test/functional/test_dirty.rb

@@ -106,6 +106,15 @@ def setup
       doc = @document.new
       doc.value_changed?.should be_false
     end
+
+    should "be false if the same ObjectId was assigned in String format" do
+      @document.key :doc_id, ObjectId
+
+      doc = @document.create!(:doc_id => BSON::ObjectId.new)
+      doc.changed?.should be_false
+      doc.doc_id = doc.doc_id.to_s
+      doc.changed?.should be_false
+    end
   end
 
   context "changes" do

test/unit/test_extensions.rb

@@ -137,6 +137,10 @@ class SupportTest < Test::Unit::TestCase
     should "leave nil values nil" do
       Float.to_mongo(nil).should == nil
     end
+
+    should "leave blank values nil" do
+      Float.to_mongo('').should == nil
+    end
   end
 
   context "Hash.from_mongo" do