fields.py 文件源码

def __get__(self, instance, owner):
        if instance is None:
            # Document class being used rather than a document object
            return self

        # Get value from document instance if available
        value = instance._data.get(self.name)
        self._auto_dereference = instance._fields[self.name]._auto_dereference
        # Dereference DBRefs
        if self._auto_dereference and isinstance(value, DBRef):
            dereferenced = self.document_type._get_db().dereference(value)
            if dereferenced is None:
                raise DoesNotExist('Trying to dereference unknown document %s' % value)
            else:
                instance._data[self.name] = self.document_type._from_son(dereferenced)

        return super(CachedReferenceField, self).__get__(instance, owner)