Abstract Data Types with only virtual functions - C++ Class

C++ examples for Class:Virtual Function

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Description

Abstract Data Types with only virtual functions

Demo Code

                                                                       
#include <iostream> 
                                                                        
class Shape //from   w ww.  ja  v  a 2s.c o m
{ 
public: 
    Shape() {} 
    virtual ~Shape() {} 
    virtual long getArea() { return -1; } // error 
    virtual long getPerim() { return -1; } 
    virtual void draw() {} 
}; 
                                                                        
class Circle : public Shape 
{ 
public: 
    Circle(int newRadius):radius(newRadius) {} 
    ~Circle() {} 
    long getArea() { return 3 * radius * radius; } 
    long getPerim() { return 9 * radius; } 
    void draw(); 
private: 
    int radius; 
    int circumference; 
}; 
                                                                        
void Circle::draw() 
{ 
    std::cout << "Circle drawing routine here!\n"; 
} 
                                                                        
class Rectangle : public Shape 
{ 
public: 
    Rectangle(int newLen, int newWidth): 
          length(newLen), width(newWidth) {} 
    virtual ~Rectangle() {} 
    virtual long getArea() { return length * width; } 
    virtual long getPerim() { return 2 * length + 2 * width; } 
    virtual int getLength() { return length; } 
    virtual int getWidth() { return width; } 
    virtual void draw(); 
private: 
    int width; 
    int length; 
}; 
                                                                        
void Rectangle::draw() 
{ 
    for (int i = 0; i < length; i++) 
    { 
        for (int j = 0; j < width; j++) 
            std::cout << "x "; 
                                                                        
        std::cout << "\n"; 
    } 
} 
                                                                        
class Square : public Rectangle 
{ 
public: 
    Square(int len); 
    Square(int len, int width); 
    ~Square() {} 
    long getPerim() { return 4 * getLength(); } 
}; 
                                                                        
Square::Square(int newLen): 
    Rectangle(newLen, newLen) 
{} 
                                                                        
Square::Square(int newLen, int newWidth): 
    Rectangle(newLen, newWidth) 
{ 
    if (getLength() != getWidth()) 
         std::cout << "Error, not a square ... a rectangle?\n"; 
} 
                                                                        
int main() 
{ 
    int choice; 
    bool fQuit = false; 
    Shape * sp; 
                                                                        
    while (1) 
    { 
         std::cout << "(1) Circle (2) Rectangle (3) Square (0) Quit: "; 
         std::cin >> choice; 
                                                                        
         switch (choice) 
          { 
         case 1: 
              sp = new Circle(5); 
              break; 
         case 2: 
                sp = new Rectangle(4, 6); 
                break; 
           case 3: 
                sp = new Square(5); 
                break; 
           default: 
                fQuit = true; 
                break; 
           } 
           if (fQuit) 
                break; 
                                                                        
           sp->draw(); 
           std::cout << "\n"; 
    } 
    return 0; 
}

Result


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