好友功能无法访问私有成员

Friend function can't access private members

我正在尝试获取 class1ships 的友元函数来访问两者的私有成员,但它说这些成员不可访问。

代码如下,问题在ships.cpp。我试图在一个文件中以更简单的方式重现这个问题,但它并没有在那里发生,所以我不知道这里出了什么问题。可能是循环声明的问题?

ships.h

#ifndef  _SHIPS_H_
#define _SHIPS_H_

#include "point.h"

class class1;

class Ships{
public:
    friend char* checkpoints();
private:
    Point ship[6]; 
};
#endif // ! _SHIPS_H_

ships.cpp

#include "ships.h"
#include "class1.h"

char* checkpoints(Ships ship, class1 game) {

    ship.ship[0];//cannot access private member declared in class 'Ships'
    game.smallship;//cannot access private member declared in class 'class1'

    return nullptr;
}

class1.h

#ifndef _CLASS1_H_
#define _CLASS1_H_

#include  "ships.h"
class class1 {
public:
    friend char* checkpoints();
private:
    static const int LIVES = 3;
    Ships smallship, bigship;
};

#endif 

只是让我的评论成为答案。您将 char* checkpoints() 声明为友元函数。将正确的原型 char* checkpoints(Ships ship, class1 game) 声明为朋友。

您可能还想使用引用(可能是 const),否则参数将按值传递(复制):char* checkpoints(Ships& ship, class1& game)