Sorry about the long delay... On 02/08/2012 09:24 AM, Paul-Cristian Manta wrote:
In my application I have a base Event class and both C++ and Python inherit from this base and define new types of events. Clients can subscribe a certain function to a certain type of event. >>> events = EventDispatcher() >>> sub = events.subscribe(KeyboardEvent, on_keyboard_event) >>> sub.cancel() When an event is posted to theEventDispatcher (from either C++ or Python), all functions that are subscribed to that event, /or to a base of that event/, are called. Because of how the system is supposed to work, I need a common way to determine type and parents of an event at runtime, regardless of whether the event class was defined in C++ or Python; I do this with a custom EventTypeInfo class. The metaclass that I would like to define in C++ would add a __cpp_event_typeinfo attribute to each event class defined in Python, which I can then grab when I need it. *A possible solution.* I though a good enough way of defining a metaclass in Boost.Python would be to the equivalent of this code below. Do you think there are any safety problem with doing something like this, some compatibly problem that could arise with the other Boost.Python classes? >>> class Meta: ... pass ... >>> Meta = type(Meta.__name__, (type,), dict(Meta.__dict__))
This is indeed a perfectly valid way to make a metaclass, and it should definitely work to do the same thing in C++ using the C API and/or Boost.Python.
The trouble is using that metaclass as the type of a Boost.Python-wrapped C++ class...that's what I think is basically impossible.
Of course, if you just want to inject some attributes into a wrapped class, you can do that in Boost.Python without a metaclass. You'd write a function that takes a boost::python::object and adds the attributes you want to it. Calling that function with a boost::python::class_ object would then add the attribute, just like a metaclass would.
Jim _______________________________________________ Cplusplus-sig mailing list Cplusplus-sig@python.org http://mail.python.org/mailman/listinfo/cplusplus-sig
