有人会介意帮我解决C链接/编码难题吗?
我有一个类Shape . Shape需要使用类Center的私有数据成员,x和y坐标 . 我宣布朋友类Shape;然后在Shape.h中#include“center.h” . 在Shape.cpp中,我定义了我的ostream&operator <<(ostream&ostr,const Center&c)函数,它使用c.xCord; c.yCord访问中心的私人数据成员 .
当我尝试编译Shape.cpp时,我得到了那些数据变量的访问错误,比如我没有将Shape声明为友元类 . 我觉得这与编译时的链接顺序有关 . 我怎样才能解决这个问题?
#ifndef CENTER_H
#define CENTER_H
class Center
{
public:
Center(double x, double y) { xCord = x; yCord = y; }
// constructor
friend class Shape;
// allow Shape to use Center's x and y values
private:
double xCord;
// X-coordinate
double yCord;
// Y-coordinate
};
#endif
#ifndef SHAPE_H
#define SHAPE_H
#include "center.h"
#include <iostream>
using namespace std;
class Shape
{
public:
Shape(double x, double y) : s_center(x, y) {}
// constructor
void moveCenter();
// moves the center of the shape
friend ostream& operator<< (ostream& ostr, const Center& c);
// allows the printing of the Center object
virtual void printCenter();
// returns the center of the shape
virtual double printArea();
// returns the area of the shape
virtual bool checkSurface(Shape& s) = 0;
// checks if the shape can fit into
// a given surface
virtual double findArea() = 0;
// calculates the area of the shape
private:
Center s_center;
// center of the shape
};
#endif
// in shape.cpp
ostream& operator<< (ostream& ostr, const Center& c)
{
ostr << "(" << c.xCord << ", " << c.yCord << ")";
return ostr;
}
2 回答
根据C 11标准第11.3 / 10段:
如果类
A
是类B
的friend
,并且函数f()
是类A
的friend
,则这也不会使f()
friend
类B
.如果您希望它访问
Center
的私有成员变量,则应将operator <<
声明为Center
类Center
:您的运算符<<与类Shape无关 . 友谊不会扩展到运营商 . 您需要将该特定运算符声明为朋友 .