從兩個類繼承在C++

Question

假設我有一類酒精它已得到兩個派生類的類：葡萄酒和啤酒。如果我會做一個類蘋果酒繼承酒和啤酒以及如何？

酒精將出現蘋果酒類？

我知道它可以用虛擬繼承來完成，沒有它但是會有什麼區別？

Answer 1

非虛擬繼承：

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 

虛繼承：

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

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

在非虛擬情況下，有兩個disctinct基地子對象。我們來看看他們：

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

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