Pure Virtual Functions - C++ Class

C++ examples for Class:Virtual Function

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Description

Pure Virtual Functions

Demo Code

                                                                       
#include <iostream> 
                                                                        
class Shape /*from ww  w  .  j a  v  a  2 s. c  o m*/
{ 
public: 
    Shape() {} 
    virtual ~Shape() {} 
    virtual long getArea() = 0; 
    virtual long getPerim()= 0; 
    virtual void draw() = 0; 
private: 
}; 
                                                                        
void Shape::draw() 
{ 
    std::cout << "Abstract drawing mechanism!\n"; 
} 
                                                                        
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"; 
    Shape::draw(); 
} 
                                                                        
class Rectangle : public Shape 
{ 
public: 
    Rectangle(int newLen, int newWidth): 
         length(newLen), width(newWidth) {} 
    virtual ~Rectangle() {} 
    long getArea() { return length * width; } 
    long getPerim() { return 2 * length + 2 * width; } 
    virtual int getLength() { return length; } 
    virtual int getWidth() { return width; } 
    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"; 
    } 
    Shape::draw(); 
} 
                                                                        
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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