_register_validator

Widget._register_validator(handler: Callable[[...], None], names: tuple[str | Sentinel, ...]) → None

Setup a handler to be called when a trait should be cross validated.

This is used to setup dynamic notifications for cross-validation.

If a validator is already registered for any of the provided names, a TraitError is raised and no new validator is registered.

Parameters:

  • handler (callable) –

    A callable that is called when the given trait is cross-validated. Its signature is handler(proposal), where proposal is a Bunch (dictionary with attribute access) with the following attributes/keys:

    • owner : the HasTraits instance

    • value : the proposed value for the modified trait attribute

    • trait : the TraitType instance associated with the attribute

  • names (List of strings) – The names of the traits that should be cross-validated