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C++ Keywords - virtual

Updated: 2022-02-08

Used for Runtime polymorphism:

  • the resolving of function call is done at runtime
  • runtime polymorphism is achieved only through a pointer (or reference) of base class type.
  • not mandatory for the derived class to override

Pure Virtual Function

A pure virtual function is declared by assigning 0 in declaration.

virtual void foo() = 0;

Abstract methods in Java is same as pure virtual functions in C++. virtual functions in c++ can be overridden , but abstract method must be overridden or the class must be abstract too.This is because virtual function have a default implementation and abstract methods have none.

C++ A class is abstract if it has at least one pure virtual function.

In C++, an interface can be simulated by making all methods as pure virtual.

Compile-time(early binding) VS run-time(late binding)

Virtual Destructor

Rule of thumb: add a virtual destructor (even an empty one) if there's any virtual function in a class.