On 05/25/2011 02:26 PM, Jay Riley wrote:
I have some class functions that takes in parameters by pointer.
However, when I expose and override this class/these functions in
boost::python, any changes I make to the parameters are not reflected
back to the original, meaning it isn't being passed by pointer as I
expect. I previously had them as pass-by-reference, but the same problem
still occurred. For an example of what I mean, here's some of my code
with unimportant functions and details omitted.
I note two spots that bear further investigation.
The most likely source is here:
//In the actual scripting code
void StatusEffectWrapper::TickCharacter(Game::Character::BaseCharacter*
character, Game::Battles::BattleField *field, int ticks)
{
call_method<void>(self, "TickCharacter", character, field, ticks);
}
I think there's a very good chance that call_method is copying your
character argument when it converts it to Python. Boost.Python is
extra-careful about making sure the C++ objects it puts inside Python
objects don't turn into dangling references, and it has no way to
control the lifetime of a raw pointer or reference. I think you could
probably fix this by using shared_ptr<BaseCharacter> here, because
Boost.Python does know how to convert that safely to Python without
copying the pointee.
If that fails, look here:
.def("TickCharacter", &StatusEffect::TickCharacter,
&StatusEffectWrapper::TickCharacterDefault)
I've personally never seen this invocation of .def, with two member
function pointer arguments. That doesn't necessarily mean it's
incorrect, because overloading virtual methods in Python is feature I
almost never use, and it seems like there are a half-dozen ways to do it
and I never know which one is considered best (perhaps someone else on
this list does?). But you might want to make sure this does what you
expect.
HTH
Jim Bosch
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