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C++ Interface

Interfaces in C++ (Abstract Classes)

Interfaces in C++ are basically the abstract classes that are used to achieve the abstraction in C++. It can be described as the process that is used to show the functionality only and hide the internal details. Generally there are two methods in which abstraction can be achieved:

  • Abstract class
  • Interface

The above mentioned methods can possess the abstract methods that are necessary for abstraction.

C++ Abstract class

A class in C++ is made to be abstract just by declaring one of its functions at least as <>strong> pure virtual function. A pure virtual function is generally specified by placing “=0” in its declaration. The derived class should have the implementation delivered by them.

Here is an example of the abstract class in C++ that consists of one abstract method and the implementation has been delivered by the classes, this example will help you understand the physical aspect of the abstract class:

#include 
using namespace std;
//Parent class
class Shapes {
   public:
      virtual int Area() = 0;
      void setWid(int x) 
	  {
         width = x;
      }
   
      void setHei(int y) 
	  {
         height = y;
      }
   
   protected:
  int width;
  int height;
};
 
// Child classes
class Rect: public Shapes 
{
   public:
      int Area() 
	  { 
         return (width * height); 
      }
};

class Tri: public Shapes 
{
   public:
      int Area() 
	  { 
         return (width * height)/2; 
      }
};
 
int main(void) {
   Rect obj;
   Tri  obj1;
 
   obj.setWid(10);
   obj.setHei(15);
   
   cout << "Total Rect area = " << obj.Area() << endl;

   obj1.setWid(10);
   obj1.setHei(15);
   
   // Print the area of the object.
   cout << "Total Trian area = " <
Output : Total Rect area = 150 Total Trian area = 75

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