Skip to Main Content
C++ Cookbook
book

C++ Cookbook

by D. Ryan Stephens, Christopher Diggins, Jonathan Turkanis, Jeff Cogswell
November 2005
Beginner to intermediate content levelBeginner to intermediate
594 pages
16h 23m
English
O'Reilly Media, Inc.
Content preview from C++ Cookbook

15.2. Using Pointers to Class Members

Problem

You need to refer to a data member or a member function with its address.

Solution

Use the class name and the scope operator (::) with an asterisk to correctly qualify the name. Example 15-2 shows how.

Example 15-2. Obtaining a pointer to a member

#include <iostream>
#include <string>

class MyClass {

public:
   MyClass() : ival_(0), sval_("foo") {}
  ~MyClass() {}

   void incr() {++ival_;}
   void decr() {ival_--;}

private:
   std::string sval_;
   int ival_;
};

int main() {

   MyClass obj;

   int         MyClass::* mpi = &MyClass::ival_;  // Data member
   std::string MyClass::* mps = &MyClass::sval_;  // pointers

   void (MyClass::*mpf)(); // A pointer to a member function that
                           // takes no params and returns void
   void (*pf)();           // A normal function pointer

   int* pi = &obj.ival_;   // int pointer referring to int member--no
                           // problem.

   mpf = &MyClass::incr;   // A pointer to a member function. You can't
                           // write this value to a stream. Look at it
                           // in your debugger to see what its
                           // representation looks like.

   pf = &MyClass::incr;    // Error: &MyClass::incr is not an instance
                           // of a function

   std::cout << "mpi = " << mpi << '\n';
   std::cout << "mps = " << mps << '\n';
   std::cout << "pi =  " << pi << '\n';
   std::cout << "*pi = " << *pi << '\n';

   obj.*mpi = 5;
   obj.*mps = "bar";

   (obj.*mpf)(); // now obj.ival_ is 6

   std::cout << "obj.ival_ = " << obj.ival_ << '\n';
   std::cout << "obj.sval_ = " << obj.sval_ << '\n';
}

Discussion

Pointers to members look and act differently than ordinary pointers. ...

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Start your free trial

You might also like

C++ System Programming Cookbook

C++ System Programming Cookbook

Onorato Vaticone

Publisher Resources

ISBN: 0596007612Supplemental ContentErrata Page