Simplify serialization slightly

rest_framework/fields.py

@@ -202,12 +202,15 @@ class Field(object):
             return self.default_empty_html if (ret == '') else ret
         return dictionary.get(self.field_name, empty)
 
-    def get_attribute(self, instance):
+    def get_field_representation(self, instance):
         """
-        Given the *outgoing* object instance, return the value for this field
-        that should be returned as a primative value.
+        Given the outgoing object instance, return the primative value
+        that should be used for this field.
         """
-        return get_attribute(instance, self.source_attrs)
+        attribute = get_attribute(instance, self.source_attrs)
+        if attribute is None:
+            return None
+        return self.to_representation(attribute)
 
     def get_default(self):
         """

rest_framework/serializers.py

@@ -268,8 +268,7 @@ class Serializer(BaseSerializer):
         fields = [field for field in self.fields.values() if not field.write_only]
 
         for field in fields:
-            native_value = field.get_attribute(instance)
-            ret[field.field_name] = field.to_representation(native_value)
+            ret[field.field_name] = field.get_field_representation(instance)
 
         return ret