class CommandBus(api.CommandBus):
def __init__(
self,
*,
middlewares: t.List[api.Middleware] = None,
allow_result: bool = True,
locking: bool = True,
) -> None:
self._messagebus = MessageBus(middlewares=middlewares)
self._allow_result = bool(allow_result)
self._locking = bool(locking)
self._is_processing_a_message = False
def add_handler(self, message_class: type,
message_handler: t.Callable) -> None:
if self._messagebus.has_handler_for(message_class):
raise api.CommandHandlerAlreadyRegisteredForAType(
f"A command handler is already registed for message class '{message_class}'."
)
self._messagebus.add_handler(message_class, message_handler)
def handle(self, message: object) -> t.Any:
if not self._messagebus.has_handler_for(message.__class__):
raise api.CommandHandlerNotFound(
f"No command handler is registered for message class '{message.__class__}'."
)
if self._locking and self._is_processing_a_message:
raise api.CommandBusAlreadyProcessingAMessage(
f"CommandBus already processing a message when received a '{message.__class__}' one." # pylint: disable=line-too-long
)
self._is_processing_a_message = True
result = self._messagebus.handle(message)
self._is_processing_a_message = False
return result[0] if self._allow_result else None
def has_handler_for(self, message_class: type) -> bool:
return self._messagebus.has_handler_for(message_class)
def test_has_handler_for():
sut = MessageBus()
sut.add_handler(MessageClassOne, get_one)
assert sut.has_handler_for(MessageClassOne) is True
assert sut.has_handler_for(MessageClassTwo) is False