Syntax:

    virtual return-type name( parameter-list );
    virtual return-type name( parameter-list ) = 0;

The virtual keyword can be used to create virtual functions, which can be overridden by derived classes.

* A virtual function indicates that a function can be overridden in a subclass,

  and that the overridden function will actually be used.

  function, the decision about which version of that function to call is based
  on the type of object pointed to by the pointer, and this process happens at
  runtime.

  versions of the virtual function run.

If the function is specified as a pure virtual function (denoted by the = 0), it must be overridden by a derived class. Example code: For example, the following code snippet shows how a child class can override a virtual method of its parent, and how a non-virtual method in the parent cannot be overridden:

  class Base {
  public:
   void nonVirtualFunc() {
     cout << "Base: non-virtual function" << endl;
   }
   virtual void virtualFunc() {
     cout << "Base: virtual function" << endl;
   }
  };

  class Child : public Base {
  public:
   void nonVirtualFunc() {
     cout << "Child: non-virtual function" << endl;
   }
   void virtualFunc() {
     cout << "Child: virtual function" << endl;
   }
  };

  int main() {
   Base* basePointer = new Child();
   basePointer->nonVirtualFunc();
   basePointer->virtualFunc();
   return 0;
  }

When run, the above code displays:

  Base: non-virtual function
  Child: virtual function

Related Topics: class