Question

I have an object that can contain references to other objects of the same type. In my validator I want to ensure the references are not to itself. Is this possible to do?

class MyObject(db.Model):

  def not_self_validator(value):
    if self._my_entity == value: #something like this..
      logging.warn('attempted to set object to itself')
      raise ValueError('Unable to set an object to itself')

  _my_entity = db.ReferenceProperty(db._SELF_REFERENCE,required=False,default=None,validator=not_self_validator)

Answer 1

The property validator can receive any method/function, but it is not possible to bond that method to self. However you can adapt your validation routine to something like this:

def not_self_validator(value):
  #is checks for same address(pointer) whereas == will call the equality method
  if value._my_entity is value:
    logging.warn('attempted to set object to itself')
    raise ValueError('Unable to set an object to itself')