从两个类继承在C++

Question

假设我有一类酒精它已得到两个派生类的类：葡萄酒和啤酒。如果我会做一个类苹果酒继承酒和啤酒以及如何？

酒精将出现苹果酒类？

我知道它可以用虚拟继承来完成，没有它但是会有什么区别？

Answer 1

非虚拟继承：

struct Beer : Alcohol {}; 
struct Wine : Alcohol {};   // I'll have what he's having! 

Alcohol Alcohol     // ...whe-ere'sh my... bayshe clashhh... hic 
^  ^
    |   | 
Beer  Wine 
    ^ ^
    \ /
     \ /
     Cider 

虚继承：

struct Beer : virtual Alcohol {}; // virtual = doesn't get you drunk 
struct Wine : virtual Alcohol {}; 

 Alcohol      // you can see clearly now 
    ^ ^
    /  \ 
Beer  Wine 
    ^ ^
    \ /
     \ /
     Cider 

在非虚拟情况下，有两个disctinct基地子对象。我们来看看他们：

Cider x; 
Alcohol & a1 = static_cast<Beer&>(x); 
Alcohol & a2 = static_cast<Wine&>(x); 

assert(std::addressof(a1) != std::addressof(a2));