C++ LANGUAGE POINTER TO C++ CLASSES

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C++ LANGUAGE POINTER TO C++ CLASSES

Pointer to C++ Classes 


A pointer to a C++ class is done exactly the same way as 
a pointer to a structure and to access members of a pointer 
to a class you use the member access operator -> operator, 
just as you do with pointers to structures. Also as with all 
pointers, you must initialize the pointer before using it. 

Let us try the following example to understand the concept of pointer to a class: 

#include <iostream> 
  
using namespace std; 
 
class Box 
{ 
   public: 
      // Constructor definition 
      Box(double l=2.0, double b=2.0, double h=2.0) 
      { 
         cout <<"Constructor called." << endl; 
         length = l; 
         breadth = b; 
         height = h; 
      } 
      double Volume() 
      { 
         return length * breadth * height; 
      } 
   private: 
      double length;     // Length of a box 
      double breadth;    // Breadth of a box 
      double height;     // Height of a box 
}; 
 
int main(void) 
{ 
   Box Box1(3.3, 1.2, 1.5);    // Declare box1 
   Box Box2(8.5, 6.0, 2.0);    // Declare box2 
   Box *ptrBox;                // Declare pointer to a class. 
 
   // Save the address of first object 
   ptrBox = &Box1; 
 
   // Now try to access a member using member access operator 
   cout << "Volume of Box1: " << ptrBox->Volume() << endl; 
 
   // Save the address of first object 
   ptrBox = &Box2; 
 
   // Now try to access a member using member access operator 
   cout << "Volume of Box2: " << ptrBox->Volume() << endl; 
   
   return 0; 
} 
When the above code is compiled and executed, it produces the following result: 
Constructor called. 
Constructor called. 
Volume of Box1: 5.94 
Volume of Box2: 102