THINK++ — Engineering Visualized

Late Binding

Virtual Functions

Virtual functions ensure that the correct function is called for an object, regardless of the type of reference (or pointer) used for function call.

THE POWER OF VIRTUAL

Parent* p = new Child();
p->show(); 
// If show() is virtual, Child's version runs.
// If NOT virtual, Parent's version runs.

PURE VIRTUAL FUNCTIONS

virtual void draw() = 0;

Makes a class "Abstract". You cannot create objects of an abstract class. It forces derived classes to implement the function.

VTABLE & VPP

Under the hood, C++ uses a Virtual Table (vtable) and a Virtual Pointer (vptr) to perform runtime dispatching. This adds a tiny overhead to function calls.

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