如何在使用多重继承时避免死亡钻石？ [英] How can I avoid the Diamond of Death when using multiple inheritance?

问题描述

http://en.wikipedia.org/wiki/Diamond_problem

我知道这是什么意思，但是我可以采取什么步骤来避免呢？

I know what it means, but what steps can I take to avoid it?

推荐答案

class A {};
class B : public A {};
class C : public A {};
class D : public B, public C {};

注意类D从B& C.但是， C继承自A。这将导致V表中包括A类的2个副本。

Notice how class D inherits from both B & C. But both B & C inherit from A. That will result in 2 copies of the class A being included in the vtable.

为了解决这个问题，我们需要虚拟继承。它是需要被虚拟继承的A类。因此，这将解决问题：

To solve this, we need virtual inheritance. It's class A that needs to be virtually inherited. So, this will fix the issue:

class A {};
class B : virtual public A {};
class C : virtual public A {};
class D : public B, public C {};

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