C++ FAQ - How do I use Virtual Destructor?

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We can have virtual destructor. It is very useful when you need to delete the object using base class pointers, especially when you implement polymorphism.

Source Code

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class Shape

{

public:

    Shape()

    {

        std::cout << "Calling Shape Constructor\n";

    }

    virtual ~Shape()  // Pure Virtual Destructor

    {

        std::cout << "Calling Shape Destructor\n\n";

    }

    virtual void draw() = 0;  // Pure Virtual Function

    virtual void display() { };

};

 

class Rect1 : public Shape

{

    int l,b;

public:

    virtual ~Rect1()

    {

        std::cout << "Calling Rectangle Destructor\n";

    }

    Rect1()

    {

        std::cout << "Calling Rectangle Constructor\n\n";

    }

    virtual void draw() {}

    virtual void display() { };

};

 

class Circle : public Shape

{

    int r;

public:

    virtual ~Circle()

    {

        std::cout << "Calling Circle Destructor\n";

    }

    Circle()

    {

        std::cout << "Calling Circle Constructor\n\n";

    }

    virtual void draw() {};

    virtual void display() { };

};

 

class Triangle : public Shape

{

    int a,b,c;

public:

    virtual ~Triangle()

    {

        std::cout << "Calling Triangle Destructor\n";

    };

    Triangle()

    {

        std::cout << "Calling Triangle Constructor\n\n";

    }

    virtual void draw() {};

    virtual void display() { };

};

 

 

int _tmain(int argc, _TCHAR* argv[])

{

 

    Shape *p[]  = {

              new Rect1(),

              new Circle(),

              new Triangle(),

    };

 

    for(int i = 0; i < sizeof(p) / sizeof(p[0]); i++)

        delete p[i];

 

    return 0;

}

Output

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