友谊和继承有什么区别？ [英] What's the difference between friendship and inheritance?

问题描述

假设有两个A和B类：

class A {};
class B {};

以下两个例子在哪些方面有所区别？

In what aspects differ the two examples below?

示例1：

class C : public A, public B {}; 

示例2：

class C
{
    //private
    friend class A;
    friend class B;
}

推荐答案

A 朋友可以触摸任何朋友的私人部分（只是有点故意！;）），但没有任何 A 和 B 是 C 的一部分 - 它只是意味着 A 和 B 可以触及 C 的私有位）。 A 和 B 私人。 c $ c>，所以如果 C 有受保护或公开会员，也将可用。

A friend can touch the private parts (pun only slightly intentional! ;) ) of whatever it is friend of, but nothing of A and B are part of C - it just means that "A and B can touch C's private bits"). Anything "less" than private is of course also available to A and B, so if C has protected or public members, that will also be available.

当你继承时， A 和 B 成为 C 的一部分。 A 和 B 的任何私有部分均不可用于 C 。在is-a与has-a命名法中， C 现在是-$ A 并且是-a B - 换句话说，它继承自 A ，所以它表现得像从接口角度看。

When you inherit, the A and B becomes part of C. Any private sections of A and B are not available to C. In the "is-a" vs. "has-a" nomenclature, C now is-a A and is-a B - in other words, it's inherited from A, so it "behaves like A from an interface perspective.

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