fields.py 文件源码

def to_mongo(self, document):
        if isinstance(document, DBRef):
            if not self.dbref:
                return document.id
            return document

        if isinstance(document, Document):
            # We need the id from the saved object to create the DBRef
            id_ = document.pk
            if id_ is None:
                self.error('You can only reference documents once they have'
                           ' been saved to the database')

            # Use the attributes from the document instance, so that they
            # override the attributes of this field's document type
            cls = document
        else:
            id_ = document
            cls = self.document_type

        id_field_name = cls._meta['id_field']
        id_field = cls._fields[id_field_name]

        id_ = id_field.to_mongo(id_)
        if self.document_type._meta.get('abstract'):
            collection = cls._get_collection_name()
            return DBRef(collection, id_, cls=cls._class_name)
        elif self.dbref:
            collection = cls._get_collection_name()
            return DBRef(collection, id_)

        return id_