Question

look at this code

#include<iostream>

using namespace std;

    //Shape is an Interface Class. No data and everything pure virtual
    class Shape {
    public:
      virtual void Area(int length, int breadth) = 0;
      virtual void Perimeter(int length, int breadth) = 0;
      //Note, no data
    };

    //Derived class - Inherits Shape as Public
    class Rectangle : public Shape {
    public:
      void Area(int length, int breadth);
      void Perimeter(int length, int breadth);
    private:
      int someData;
    };

    //Derived class - Inherits Shape as Public
    class Triangle : public Shape {
    public:
      void Area(int length, int breadth);
      void Perimeter(int length, int breadth);
    private:
      int someData;
    };

    int main()
    {
      Rectangle r;
      Triangle t;

      cout<<"\n\n";
      r.Area(3,4);
      r.Perimeter(3,4);

      t.Area(3,4);
      t.Perimeter(3,4);

      cout<<"\n\n";
      return 0;
    }

    void Rectangle::Area(int length, int breadth)
    {
      cout<<"\nThe Area of Rectangle for length = "<<length<<" and\
      breadth = "<<breadth<<" is "<<(length * breadth)<<endl;
    }

    void Rectangle::Perimeter(int length, int breadth)
    {
      cout<<"\nThe Perimeter of Rectangle for length = "<<length<<" and\
      breadth = "<<breadth<<" is "<<2 * (length + breadth)<<endl;
    }

    void Triangle::Area(int length, int breadth)
    {
      cout<<"\nThe Area of Triangle for length = "<<length<<" and\
      breadth = "<<breadth<<" is "<<(length * breadth)/2<<endl;
    }

    void Triangle::Perimeter(int length, int breadth)
    {
      cout<<"\nThe Perimeter of Triangle for length = "<<length<<" and\
      breadth = "<<breadth<<" is "<<(length * breadth)/3<<endl;
    }

I use interface in the code , but my question is what i should use it and what is the benefits from it , no performance , no real needed it , why i should i use it ( the interfaces ) . what is the point to use it , an you explain it please .

and thank you !

Answer 1

Abstract interfaces separate the interface from the implementation. Just as pimpl idiom it

• decreases compilation time, and
• lets you change the implementation without breaking the ABI.

Both are important advantages in large programs.