Question

To be more specific:

class B;
class A
{
    public:
        A(B &b) : _b(b) { }
        ~A() { _b.do_something(); }

    private:
        B &_b;
};

class B
{
    public:
        B() { }

        /** other methods */

        ~B()
        {
            for (std::list<A*>::iterator it = _bees.begin(); it != _bees.end(); ++it) {
                delete *it;
            }
        }
        void do_something();

    private:
         std::list<A*> _bees;
};

Is it ok to do that?

Answer 1

You are referencing b in A::~A () and not _b, which will not compile. Assuming that you meant _b, then answer is – it depends. It depends on a lifetime of the object of class B that is being references by A. If object of class B is destroyed before destructor of A class is called, then it is not OK, otherwise it is OK. In either case this code is not very fool proof, and many will consider re-designing to make it less dangerous.

If there is no strong guarantee that B will still be there when A is destroyed, then you need to do a bit a re-design. You can, for example, store B by value (copy it), or use reference counted or other “smart” pointers.