Class LazyReference

mongoengine/base/datastructures.py:437–473

class LazyReference(DBRef):
    __slots__ = ("_cached_doc", "passthrough", "document_type")

    def fetch(self, force=False):
        if not self._cached_doc or force:
            self._cached_doc = self.document_type.objects.get(pk=self.pk)
            if not self._cached_doc:
                raise DoesNotExist("Trying to dereference unknown document %s" % (self))
        return self._cached_doc

    @property
    def pk(self):
        return self.id

    def __init__(self, document_type, pk, cached_doc=None, passthrough=False):
        self.document_type = document_type
        self._cached_doc = cached_doc
        self.passthrough = passthrough
        super().__init__(self.document_type._get_collection_name(), pk)

    def __getitem__(self, name):
        if not self.passthrough:
            raise KeyError()
        document = self.fetch()
        return document[name]

    def __getattr__(self, name):
        if not object.__getattribute__(self, "passthrough"):
            raise AttributeError()
        document = self.fetch()
        try:
            return document[name]
        except KeyError:
            raise AttributeError()

    def __repr__(self):
        return f"<LazyReference({self.document_type}, {self.pk!r})>"