我是C++的新手，想知道为什么c++使用纯虚拟function？ 为什么要用纯虚拟function？

Question

I am new in C++, I want to know, why the pure virtual function is used in c++?. Somewhat I know to make class abstract and force all derived Classes to have implementation. But I want to know what is the situation where only pure virtual function can work?

Answer 1

Assume you have a certain base class defining a type like GeometricForm which has a virtual function float calculateArea() . You cannot calculate the area for GeometricForm because GeometricForm itself does not define a geometric form (hope this is understandable). But you can create a derived class eg Circle of this base class which is an actual geometric form.

You now want to be sure that this derived class implements a valid version of your former virtual function calculateArea() , which will be ensured by the compiler.