Editing Virtual function (section)

== Purpose ==
{{further|Dynamic dispatch}}
The concept of the virtual function solves the following problem:

In [[object-oriented programming]], when a derived class inherits from a base class, an object of the derived class may be referred to via a [[Pointer (computer programming)|pointer]] or [[Reference (computer science)|reference]] of the base class type instead of the derived class type. If there are base class methods overridden by the derived class, the method actually called by such a reference or pointer can be bound (linked) either "early" (by the compiler), according to the declared type of the pointer or reference, or "late" (i.e., by the runtime system of the language), according to the actual type of the object referred to.

Virtual functions are resolved "late". If the function in question is "virtual" in the base class, the most-derived class's implementation of the function is called according to the actual type of the object referred to, regardless of the declared type of the pointer or reference. If it is not "virtual", the method is resolved "early" and selected according to the declared type of the pointer or reference.

Virtual functions allow a program to call methods that don't necessarily even exist at the moment the code is compiled.{{Citation needed|date=October 2021}}

In C++, ''virtual methods'' are declared by prepending the {{Cpp|virtual}} keyword to the function's declaration in the base class. This modifier is inherited by all implementations of that method in derived classes, meaning that they can continue to over-ride each other and be late-bound. And even if methods owned by the base class call the virtual method, they will instead be calling the derived method. ''Overloading'' occurs when two or more methods in one class have the same method name but different parameters. ''Overriding'' means having two methods with the same method name and parameters. Overloading is also referred to as function matching, and overriding as dynamic function mapping.