ptrtoclss.cpp

#include <iostream>
using namespace std;

class Rectangle {
	private:
 		int length;
 		int breadth;
 	public:
 		Rectangle(int l, int b) {
 			length=l;
 			breadth=b;
		}
 		int getArea() {
 			return 2*length*breadth;
		}
};

int main() {
//// Pointer to Class
	// First approach: Create an object first, then assign to a pointer
	// creating an object of Rectangle
  Rectangle var1(5,2); // parameterized constrcutor

  /* creating a pointer of Rectangle type &
    assigning address of var1 to this pointer */
	Rectangle* ptr = &var1;

	// Second approach: directly use the new operator to assign a class/datatype to a pointer
	Rectangle* ptr = new Rectangle(5,2);//&var1;

  /* calculating area of rectangle by using pointer
  ptr to call the objects getArea() function
  */
  int area = ptr->getArea();
  cout<<"Area of rectangle is: "<< area << endl;

	// Second approach: free the allocated memory when using the new operator
	delete ptr;

// Pointer to an array
	int *ptr;
	int arr[5]={0,1,2,3,4};
	ptr = arr; //&arr[0]; // both ways are ok, both point to the first element
	for(int i=0;i<5;i++){
		// ptr+i is equivalent to &arr[i], display the address stored in ptr+i
		cout << "ptr + " << i << " = "<< ptr + i << endl;
		// *(ptr+i) is equivalent to arr[i], display the value at the address stored in ptr+i
		cout << "*(ptr + " << i << ") : " << *(ptr + i) << endl;
	}


// Pointer to Class Array
	// creating an object array of Rectangle, setting values of array elements
  Rectangle var[2] = {Rectangle(5,2), Rectangle(3,2)};

  /* creating a pointer of Rectangle type &
    assigning address of var to this pointer */
  Rectangle* ptr;
  ptr = var;

  /* calculating area of rectangles by using pointer
  ptr to call the objects getArea() function
  */
  for(int i=0;i<2;i++){
 		cout<<"Area of Rectangle"<<(i+1)<<" : "<<(ptr+i)->getArea()<<endl;
  }

 	return 0;
}