Refactor refresh method in objects for reuse

This change refactors the "refresh" method in ironic.objects.chassis,
ironic.objects.conductor, ironic.objects.node and ironic.objects.port to
reuse a more generic method added to ironic.objects.base.IronicObject
for identifying and applying changes of fields. It make the code in
refresh method more simpler to understand by removing details of
implementation, in addition decreases the code replication in four
classes.

Change-Id: I6171203690cfd282fa1250dbe0204151f5c665fb

ironic/objects/base.py

@@ -399,6 +399,18 @@ class IronicObject(ovo_base.VersionedObjectDictCompat):
                     for k in self.fields
                     if hasattr(self, k))
 
+    def obj_refresh(self, loaded_object):
+        """Applies updates for objects that inherit from base.IronicObject.
+
+        Checks for updated attributes in an object. Updates are applied from
+        the loaded object column by column in comparison with the current
+        object.
+        """
+        for field in self.fields:
+            if (hasattr(self, get_attrname(field)) and
+                    self[field] != loaded_object[field]):
+                self[field] = loaded_object[field]
+
 
 class ObjectListBase(object):
     """Mixin class for lists of objects.

ironic/objects/chassis.py

@@ -180,7 +180,4 @@ class Chassis(base.IronicObject):
                         object, e.g.: Chassis(context)
         """
         current = self.__class__.get_by_uuid(self._context, uuid=self.uuid)
-        for field in self.fields:
-            if (hasattr(self, base.get_attrname(field)) and
-                    self[field] != current[field]):
-                self[field] = current[field]
+        self.obj_refresh(current)

ironic/objects/conductor.py

@@ -72,10 +72,7 @@ class Conductor(base.IronicObject):
         """
         current = self.__class__.get_by_hostname(self._context,
                                                  hostname=self.hostname)
-        for field in self.fields:
-            if (hasattr(self, base.get_attrname(field)) and
-                    self[field] != current[field]):
-                self[field] = current[field]
+        self.obj_refresh(current)
 
     @base.remotable
     def touch(self, context):

ironic/objects/node.py

@@ -282,10 +282,7 @@ class Node(base.IronicObject):
                         object, e.g.: Node(context)
         """
         current = self.__class__.get_by_uuid(self._context, self.uuid)
-        for field in self.fields:
-            if (hasattr(self, base.get_attrname(field)) and
-                    self[field] != current[field]):
-                self[field] = current[field]
+        self.obj_refresh(current)
 
     @base.remotable
     def touch_provisioning(self, context=None):

ironic/objects/port.py

@@ -211,7 +211,4 @@ class Port(base.IronicObject):
                         object, e.g.: Port(context)
         """
         current = self.__class__.get_by_uuid(self._context, uuid=self.uuid)
-        for field in self.fields:
-            if (hasattr(self, base.get_attrname(field)) and
-                    self[field] != current[field]):
-                self[field] = current[field]
+        self.obj_refresh(current)

ironic/tests/objects/test_objects.py

@@ -444,6 +444,20 @@ class _TestObject(object):
         self.assertEqual(set(['created_at', 'updated_at', 'foo', 'bar']),
                          set(obj.obj_fields))
 
+    def test_refresh_object(self):
+        class TestObj(base.IronicObject):
+            fields = {'foo': int, 'bar': str}
+
+        obj = TestObj(self.context)
+        current_obj = TestObj(self.context)
+        obj.foo = 10
+        obj.bar = 'obj.bar'
+        current_obj.foo = 2
+        current_obj.bar = 'current.bar'
+        obj.obj_refresh(current_obj)
+        self.assertEqual(obj.foo, 2)
+        self.assertEqual(obj.bar, 'current.bar')
+
     def test_obj_constructor(self):
         obj = MyObj(self.context, foo=123, bar='abc')
         self.assertEqual(123, obj.foo)