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isocpp.faq: Inheritance — Multiple and Virtual Inheritance Δ

NOTE: 这篇文章讲解地还不错

Do we really need multiple inheritance? Δ

In C++, abstract classes often serve as interfaces and a class can have many interfaces. Other languages – often deemed “not MI” – simply have a separate name for their equivalent to a pure abstract class: an interface.

NOTE:

1、可以使用multiple inheritance的场景: "implement multiple interface"

The reason languages provide inheritance (both single and multiple) is that language-supported inheritance is typically superior to workarounds (e.g. use of forwarding functions to sub-objects or separately allocated objects) for ease of programming, for detecting logical problems, for maintainability, and often for performance.

NOTE: 这段话所要表明的是: 虽然可以使用walkround来实现和multiple inheritance类似的效果，但是如果programming language提供了multiple inheritance，那么直接使用这个特性能够带来诸多优势。

I’ve been told that I should never use multiple inheritance. Is that right? Δ

It really bothers me when people think they know what’s best for your problem even though they’ve never seen your problem!! How can anybody possibly know that multiple inheritance won’t help you accomplish your goals without knowing your goals?!?!?!?!!!

NOTE: 表明意思是: 当人们认为他们知道如何解决你的问题时，即使他们从未见过你的问题，这真的让我很困扰!!

其实说白了就是：千万不要迷信，要具体问题具体讨论。

“One size does not fit all.”

So there are times when multiple inheritance isn’t bad?!?? Δ

If MI (multiple inheritance) helps, use it; if not, don’t.

What are some disciplines for using multiple inheritance? Δ