120     VRegistry.REGISTRY_FACTORY['%s_hooks' % event] = HooksRegistry

   120     VRegistry.REGISTRY_FACTORY['%s_hooks' % event] = HooksRegistry

   121 

   121 

   122 _MARKER = object()

   122 _MARKER = object()

   123 def entity_oldnewvalue(entity, attr):

   123 def entity_oldnewvalue(entity, attr):

   124     """returns the couple (old attr value, new attr value)

   124     """returns the couple (old attr value, new attr value)

   125     NOTE: will only work in a before_update_entity hook

   126     NOTE: will only work in a before_update_entity hook

   126     """

   127     """

   127     # get new value and remove from local dict to force a db query to

   128     # get new value and remove from local dict to force a db query to

   128     # fetch old value

   129     # fetch old value

   129     newvalue = entity.pop(attr, _MARKER)

   130     newvalue = entity.pop(attr, _MARKER)

   130     oldvalue = getattr(entity, attr)

   131     oldvalue = getattr(entity, attr)

   131     if newvalue is not _MARKER:

   132     if newvalue is not _MARKER:

   132         entity[attr] = newvalue

   133         entity[attr] = newvalue

   133     return oldvalue, newvalue

   136     return oldvalue, newvalue

   134 

   137 

   135 

   138 

   136 # some hook specific selectors #################################################

   139 # some hook specific selectors #################################################

   137 

   140