Declaring Pointers to Member Functions

Pointers to member functions consists of the member function’s return type, the class name followed by ::, the pointer’s name, and the function’s parameter list. For example, a pointer to a member function of class A that returns int and takes no arguments is defined like this (note that both pairs of parentheses are mandatory):

   class A  {  public:    int func ();    };  int (A::*pmf) (); /* pmf is a pointer to some member   function of class A that returns int  and takes no   arguments*/

In fact, a pointer to a member functions looks just like an ordinary pointer to function, except that it also contains the class's name immediately followed by the :: operator. You can invoke the member function to which pmf points like this:

   pmf = &A::func; //assign pmf  A a;  A *pa = &a;  (a.*pmf)();  // invoke a.func() // call through a pointer to an object  (pa->*pmf)();  // calls pa->func()

Pointers to member functions respect polymorphism. Thus, if you call a virtual member function through a pointer to member, the call will be resolved dynamically:

   class Base{  public:    virtual int f (int n);  };  class Derived : public Base {  public:    int f (int h); //override  };  Base *pb = new Derived;  int (Base::*pmf)(int) = &Base::f;  (pb->*pmf)(5); // call resolved as D::f(5);

Note that you cannot take the address of a class's constructor(s) and destructor.

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