Pointers to Members:
In C a pointer is created to locate the address of another variable for faster access.
Consider the following example. int x, *p;
p = &x; Pointer p is pointing to the address of x, remember a pointer is also a variable and it has its own address. The above technique is fine as long as the variable is of primary data type not in the class. If the primary data type is inside the member of a class which is known as data member then the indirection operator * is not valid, instead operator ::* must be used.
Rules for declared pointer to the class and its member:
1. Only Class and its member can be declared as pointer (M *pm).
2. Members are declared as pointer through its class (int M::* px).
3. When class is declared as pointer members must also be declared as pointer to access the member.
4. When only members are declared as pointer the member can be accessed using given synatax (object_name.*pointer-to-member)
5. When class is declared as pointer remember member must also be a pointer such member can be accessed with given syntax (object_name->*pointer-to-member)
6. Only Member function are declared as pointer void(M::*pf)(int,int), for member function the pointer must be within( ) and it must specify type of argument just like function.
7. Using only member function as pointer (op.*pf)(30,40);
8. Class and member function declared as pointer accessing is (op->*pf)(30,40);