Class _CollectionAttributeImpl

lib/sqlalchemy/orm/attributes.py:1632–2130

A collection-holding attribute that instruments changes in membership. Only handles collections of instrumented objects. InstrumentedCollectionAttribute holds an arbitrary, user-specified container object (defaulting to a list) and brokers access to the CollectionAdapter, a "view"

class _CollectionAttributeImpl(_HasCollectionAdapter, _AttributeImpl):
    """A collection-holding attribute that instruments changes in membership.

    Only handles collections of instrumented objects.

    InstrumentedCollectionAttribute holds an arbitrary, user-specified
    container object (defaulting to a list) and brokers access to the
    CollectionAdapter, a "view" onto that object that presents consistent bag
    semantics to the orm layer independent of the user data implementation.

    """

    uses_objects = True
    collection = True
    default_accepts_scalar_loader = False
    supports_population = True
    dynamic = False

    _bulk_replace_token: AttributeEventToken

    __slots__ = (
        "copy",
        "collection_factory",
        "_append_token",
        "_remove_token",
        "_bulk_replace_token",
        "_duck_typed_as",
    )

    def __init__(
        self,
        class_,
        key,
        callable_,
        dispatch,
        typecallable=None,
        trackparent=False,
        copy_function=None,
        compare_function=None,
        **kwargs,
    ):
        super().__init__(
            class_,
            key,
            callable_,
            dispatch,
            trackparent=trackparent,
            compare_function=compare_function,
            **kwargs,
        )

        if copy_function is None:
            copy_function = self.__copy
        self.copy = copy_function
        self.collection_factory = typecallable
        self._append_token = AttributeEventToken(self, OP_APPEND)
        self._remove_token = AttributeEventToken(self, OP_REMOVE)
        self._bulk_replace_token = AttributeEventToken(self, OP_BULK_REPLACE)