advantages of virtual function in c++ - Wikitechy

What are Virtual functions in C++ ?

webmaster — Fri, 19 Aug 2022 12:34:29 +0000

Virtual function is a member function which is re-defined by a derived class and declared within a base class.
When you refer to a derived class object using a reference or pointer to the base class, you can call a virtual function for that object and execute the derived class’s version of the function.
It ensures that the correct function is called for an object, regardless of the type of reference used for function call.
It is mainly used to achieve Run-time polymorphism.
In base class functions are declared with a virtual. At run time the resolving of function call is done.

Sample Code

using namespace std;
 
class base {
public:
    virtual void print()
    {
        cout << "print base class\n";
    }
 
    void show()
    {
        cout << "show base class\n";
    }
};
 
class derived : public base {
public:
    void print()
    {
        cout << "print derived class\n";
    }
 
    void show()
    {
        cout << "show derived class\n";
    }
};
 
int main()
{
    base *bptr;
    derived d;
    bptr = &d;
 
    // Virtual function, binded at runtime
    bptr->print();
 
    // Non-virtual function, binded at compile time
    bptr->show();
   
    return 0;
}

Output

Which type of inheritance needs a virtual function ?

Editor — Fri, 27 Aug 2021 00:47:53 +0000

Which type of inheritance needs a virtual function ?

A. Multi level inheritance

B. Multiple inheritance

C. Hybrid inheritance

D. All of the above

Answer : D. All of the above

Syntax for Pure Virtual Function is ?

Editor — Mon, 12 Jul 2021 22:58:10 +0000

Syntax for Pure Virtual Function is ?

A. virtual void show()==0

B. void virtual show()==0

C. virtual void show()=0

D. void virtual show()=0

Answer : B. virtual void show()==0

Explanation :

In C++, A pure virtual function or abstract function is a virtual function for which we don’t have implementation, we only declare it. A pure virtual function is declared by assigning 0 in declaration.

Syntax

// An abstract class 
class Sample
{    
    // Data members of class 
public: 
    // Pure Virtual Function 
    virtual void show() = 0; 
    
   /* Other members */
};

A virtual function that has no definition within the base class is called ?

Editor — Mon, 12 Jul 2021 22:45:35 +0000

A virtual function that has no definition within the base class is called ?

A. Pure virtual function

B. Pure static function

C. Pure Const function

D. Virtual Function

Answer : A. Pure virtual function