On 05/04/2011 08:01 AM, zeb wrote:
hi, I have some problem about transfer-ownership. C++ code is like this:
class RefCounter {
int _count;
public:
RefCounter() : _count(1) {}
virtual RefCounter() {}
void addRef() { ++_count; }
void release() { --_count; if (_count == 0) delete this; }
};
class A : public RefCounter {...};
class B {
public:
void setA(A* a) {// B takes the ownership of A.
_a = a;
a.addRef();
}
private:
A* _a;
};
So, in python, I use these classes like:
a = A() # the reference count of a is 1 now.
b = B()
b.setA(a) # B take the ownership of A, and now the reference count is 2.
a.release() # a should call release to decrease the reference count, but now
a is invalid. Python says: did not match C++ signature.
I can change the C++ code to solve this problem, but I really don't want to
change C++ code.
It's better to solve it by other way.
Is there any one could give me some advice?
You should really to let Python (and C++, for that matter) handle your
reference counting if at all possible.
The best way to do that would be to ensure your Python objects are held
inside a smart pointer (boost::intrusive_ptr would probably work). If
you set that up correctly, you should never have to call addRef() or
release() from your Python code - think of it as allowing Python to
always own one reference, which it is responsible for deleting when its
done with it.
I realize I'm being a little vague about the details - feel free to ask
more questions if you need more help, but a look through the
Boost.Python reference documentation for setting the "HeldType" of a
class_ instantiation to a smart pointer should get you started.
Good luck!
Jim Bosch
--
View this message in context:
http://boost.2283326.n4.nabble.com/transfer-ownership-problem-tp3495846p3495846.html
Sent from the Python - c++-sig mailing list archive at Nabble.com.
___
Cplusplus-sig mailing list
[email protected]
http://mail.python.org/mailman/listinfo/cplusplus-sig
___
Cplusplus-sig mailing list
[email protected]
http://mail.python.org/mailman/listinfo/cplusplus-sig
