class A
{
public:
void (*fptr)();
A(){}
~A(){}
};
class B
{
public:
B(){}
~B(){}
void test(A* a_ptr)
{
a_ptr->fptr=&print
}
void print(){cout<<"Testing";}
};
C++ Function pointers
Author
Is there a way to have a function pointer to a method of another class for a patricular instance of that class.
something like this
This gives me a error
"'&' : illegal operation on bound member function expression"
any ideas on how i can do this?
print is a member function.
You need to use a member function pointer variable to store a pointer to a member function.
You need to use a member function pointer variable to store a pointer to a member function.
Author
ok so when i do this shouldnt this print testing.
it actually doesnt do anything.
it actually doesnt do anything.
class A{public: void (B::*fptr)(); A(){} ~A(){}};class B{public: B(){} ~B(){} void test(A* a_ptr) { a_ptr->fptr=&B::print; } void print(){cout<<"Testing";}};int main(){ A* a= new A(); B b; b.test(a); a->fptr; return 0;}
a->fptr is a pointer-to-member-function. Writing a->fptr; is
the same as writing &B::print, it just evaluates to the address of a member function, discards that address, and then moves on to the next instruction.
If you wish to call a member function through a pointer-to-member-function, you must use the syntax:
(instance.*ptr)();
Where instance is an instance of type T and ptr is a pointer to a member function of that same type T. In your case, the code would be:
(b.*(a->fptr))();
the same as writing &B::print, it just evaluates to the address of a member function, discards that address, and then moves on to the next instruction.
If you wish to call a member function through a pointer-to-member-function, you must use the syntax:
(instance.*ptr)();
Where instance is an instance of type T and ptr is a pointer to a member function of that same type T. In your case, the code would be:
(b.*(a->fptr))();
Author
yes thankyou. I knew it was something like that but i just wasnt sure, i had never used function pointers before.
Thank you.
Gamedev once again pulls through :)
Thank you.
Gamedev once again pulls through :)
Pointers to member functions.
But you really, *really* shouldn't need to be doing this except in very, *very* strange circumstances. What are you trying to accomplish?
But you really, *really* shouldn't need to be doing this except in very, *very* strange circumstances. What are you trying to accomplish?
This topic is closed to new replies.
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