Re: Function pointer and functor problem

Hi

I am having a doubt about function pointers and functors. I know that
the signatures of a function pointer and a pointer to a class member
function are different. However signature of a global function and
signature of a static class function are compatible.

Here is what i want to achieve:

There are 2 unrelated classes say A and B ( they are unrelated and
hence i don't want to make them part of any inheritance structure)

I have written a timer class in which i can register multiple timers,
it takes a timeout value and a function pointer that would be invoked
when the timer times out i.e basically i want a callback mechanism on
timeout. So internally the timer is using a queue to store all these
function pointer and all these function pointers have signature void
(*ptr)( );

So the queue would be like:

typedef void (*ptr)( );
queue<ptr> timer_queue;

The problem is i want to invoke the member function of classes A and
B when a timer expires so that i can change the state of object of
class A or B.

Let me make it clear( i really suck in communication, sorry for that)

class A
{
        public:
                A( ):a(5)
                {
                }
                void timerExpired( )
                {
                        cout<<a;
                }

        private:
        int a

};

class B
{
        public:
                B():name("JOHN")
                {
                }
                void timerExpired( )
                {
                        cout<<name;
                }
        private:
                string name;

};

So i want a timer that can help me code the below code :( the
following code may not be syntactically correct )

Timer timer;
A obj_of_a;
B obj_of b
// please remember that timer uses a queue of function pointers
timer.registerTimer(A::timerExpired,6)// expires after 5 seconds

timer.registerTimer(B::timerExpired,2) // expires after 2 seconds

Problem is that these two functions are not static and if i make them
static how would i change the state of the objects ( static functions
don't have this pointer)
Is it even possible i.e to store pointers to member functions (of
different classes) in a queue and invoke them.

It can be done if i make A and B derived from class C containing a
virtual function timerExpired and then storing a functor instead of a
function pointer but i don't want to do that as in my case A and B are
not at all related.

Can it be done somehow using wrapper static functions of classes A and
B ??
Please provide some hint or guidance.

Thanks a lot for your patience
Regards
lali