为了访问一个用户定义的类里的私有数据，你必须声明全局函数为友元函数，并且在类中定义。

But to be able to reach any private data within a user defined class you have to declare the global function as a friend within the definition of the class.

youdao

为了访问一个用户定义的类里的私有数据，你必须声明全局函数为友元函数，并且在类中定义。

But to be able to reach any private data within a user defined class you have to declare the global function as a friend within the definition of the class.

youdao