And polymorphic C ++ virtual functions
Links: https://blog.csdn.net/weixin_39731083/article/details/81739340
C ++: polymorphic pure virtual function, virtual function
Links: https://blog.csdn.net/liuyizhou95/article/details/82457969
And C ++ to achieve the principles of polymorphic (virtual function and a pure virtual function)
Links: https://blog.csdn.net/qq_39477053/article/details/80322260
And the difference between virtual function pure virtual function
Links: https://blog.csdn.net/hackbuteer1/article/details/7558868