[C++-sig] Best practices for wrapping classes where instance lifecycle is managed by someone else?

[Renato Araujo]

Hi
Mikael Lind

Check: http://www.boost.org/doc/libs/1_43_0/libs/python/doc/v2/with_custodian_and_ward.html#with_custodian_and_ward-spec,
if this not work to your problem this can help you to implement a new
policy.

BR
Renato Araujo Oliveira Filho




On Fri, Jul 9, 2010 at 5:05 AM, Mikael Lind <elemel at elemel.se> wrote:
> I'm using Boost.Python to wrap Box2D, a 2D physics engine written in
> C++. The user of Box2D starts by constructing an instance of class
> b2World. The b2World class has member functions for creating and
> destroying bodies and joints (for constraining the movement of the
> bodies). The b2Body class has member functions for creating and
> destroying fixtures (for attaching collisions shapes to the body). The
> created instances are returned as raw pointers.
>
> Is there a safe and efficient way of associating a Python wrapper
> instance with a wrapped C++ instance, where the Python instance
> doesn't manage the lifecycle of the C++ instance? I was thinking of
> adding a member variable to the C++ class that tracks the Python
> wrapper instance if any has been created, and do something intelligent
> on destruction of the C++ instance, i.e. marking the Python instance
> as invalid. I would like to throw an exception if the user attempts to
> access the destructed C++ instance through the invalid Python
> instance.
>
> Is the above a good approach? If it is, has anyone got any best
> practices or recommendations for the implementation?
>
> --
> Mikael Lind
> http://elemel.se/
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