A polymorphic class that encapsulates two-dimensional shapes - C++ Class

C++ examples for Class:Polymorphism

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Description

A polymorphic class that encapsulates two-dimensional shapes

Demo Code

#include <iostream>
#include <cstdlib>
using namespace std;
class Shape {//  ww  w. j a v a 2 s  .c om
   protected:
   double x, y;
   public:
   Shape(double i, double j) {
      x = i;
      y = j;
   }
   double getx() { return x; }
   double gety() { return y; }
   virtual double area() = 0;
};
// Create a subclass of Shape for triangles.
class triangle : public Shape {
   public:
   triangle(double i, double j) : Shape(i, j) { }
   double area() {
      return x * 0.5 * y;
   }
};
// Create a subclass of Shape for rectangles.
class rectangle : public Shape {
   public:
   rectangle(double i, double j) : Shape(i, j) { }
   double area() {
      return x * y;
   }
};
// Create a subclass of Shape for circles.
class circle : public Shape {
   public:
   circle(double i, double j=0) : Shape(i, j) { }
   double area() {
      return 3.14 * x * x;
   }
} ;
// A factory for objects derived from Shape.
Shape *factory() {
   static double i = (rand() % 100) / 3.0, j = (rand() % 100) / 3.0;
   i += rand() % 10;
   j += rand() % 12;
   cout << "Generating object.\n";
   switch(rand() % 3 ) {
      case 0: return new circle(i);
      case 1: return new triangle(i, j);
      case 2: return new rectangle(i, j);
   }
   return 0;
}
bool sameshape(Shape *alpha, Shape *beta) {
   cout << "Comparing a " << typeid(*alpha).name() << " object to a " << typeid(*beta).name() << " object\n";
   if(typeid(*alpha) != typeid(*beta)) 
       return false;
   if(alpha->getx() != beta->getx() && alpha->gety() != beta->gety())  
       return false;
   return true;
}
int main()
{
   // Create a base class pointer to Shape.
   Shape *p;
   // Generate Shape objects.
   for(int i=0; i < 6; i++) {
      // Generate an object.
      p = factory();
      // Display the name of the object.
      cout << "Object is " << typeid(*p).name() << endl;
      // Display its area.
      cout << "    Area is " << p->area() << endl;
      // Keep a count of the object types that have been generated.
      if(typeid(*p) == typeid(triangle))
         cout << "    Base is " << p->getx() << " Height is "
      << p->gety() << endl;
      else if(typeid(*p) == typeid(rectangle))
      cout << "    Length is " << p->getx() << " Height is "
      << p->gety() << endl;
      else if(typeid(*p) == typeid(circle))
      cout << "    Diameter is " << p->getx() << endl;
      cout << endl;
   }
   cout << endl;
   // Make some objects to compare.
   triangle t(2, 3);
   triangle t2(2, 3);
   triangle t3(3, 2);
   rectangle r(2, 3);
   // Compare two two_d_objects.
   if(sameshape(&t, &t2))
      cout << "t and t2 are the same.\n";
   if(!sameshape(&t, &t3))
      cout << "t and t3 differ.\n";
   if(!sameshape(&t, &r))
      cout << "t and r differ.\n";
   cout << endl;
   return 0;
}

Result


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