friends keyword

最新推荐文章于 2024-04-26 15:05:45 发布

原创最新推荐文章于 2024-04-26 15:05:45 发布 · 556 阅读

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本文介绍了C++中友元机制的基本概念及其应用场景。通过友元机制，特定函数可以访问类的私有成员，而无需将整个程序暴露给这些函数。文章通过具体示例展示了如何声明和使用友元函数。

friends to function

In some cases it is convenient to allow certain functions to access the private members of a class withoutallowing access to the entire program. The friend mechanism allows a class to grant functions access to its nonpublic members.

          such as
                class Screen {
                        friend istream&   operator>>( istream&, Screen& );
                        ...
               }

                ostream& operator>> ( ostream& os, const Screen& s )
                {
                       os << s._height << s._screen;
                        return os;
                }

    COMMENTS: operator>> is the most popular usage of friends keyword, because it must be declared as friend function.

friends to whole class or namespace.

A friend may be a namespace function, a member function of another previously defined class, or an entire class. In making one class a friend, all the member functions of the friend class are given access to the nonpublic members of the class granting friendship.