C++ Pointers to members Pointers to member functions
Example
To access a member function of a class, you need to have a "handle" to the particular instance, as either the instance itself, or a pointer or reference to it. Given a class instance, you can point to various of its members with a pointer-to-member, IF you get the syntax correct! Of course, the pointer has to be declared to be of the same type as what you are pointing to...
typedef int Fn(int); // Fn is a type-of function that accepts an int and returns an int
class Class {
public:
// Note that A() is of type 'Fn'
int A(int a) { return 2*a; }
// Note that B() is of type 'Fn'
int B(int b) { return 3*b; }
}; // Class
int main() {
Class c; // Need a Class instance to play with
Class *p = &c; // Need a Class pointer to play with
Fn Class::*fn; // fn is a pointer to a type-of Fn within Class
fn = &Class::A; // fn now points to A within any Class
(c.*fn)(5); // Pass 5 to c's function A (via fn)
fn = &Class::B; // fn now points to B within any Class
(p->*fn)(6); // Pass 6 to c's (via p) function B (via fn)
} // main()
Unlike pointers to member variables (in the previous example), the association between the class instance and the member pointer need to be bound tightly together with parentheses, which looks a little strange (as though the .* and ->* aren't strange enough!)
