问题描述

C++友元的问题。不知道错在哪里。弄得恼火了。。求助。

先不要管它干什么用，要怎样修改才可以运行呢？为什么要这样修改？

void set_input(){input=(input==TV)? DVD : TV;}
void settings() const;
void ch_h(Remote &t);
void input_ch_h(Remote &t);

private:
int state;
int volume;
int maxchannel;
int channel;
int mode;
int input;
};
class Remote
{
friend class Tv;
private:
int mode;
int style;

public:
enum{changgui,hudong};
Remote(int m=Tv::TV):mode(m){}
bool volup(Tv&t){return t.volup();}
bool voldown(Tv&t){return t.voldown();}
void onoff(Tv&t){t.onoff();}
void chanup(Tv&t){t.chanup();}
void chandown(Tv&t){t.chandown();}
void set_chan(Tv&t,int c){t.channel=c;}
void set_mode(Tv&t){t.set_mode();}
void set_input(Tv&t){t.set_input();}

};
inline void Tv::ch_h(Remote &t)
{
if(t.style==Remote::hudong)
t.style=Remote::changgui;
else t.style=Remote::hudong;
}
#endif

#include"151.h"
#include
bool Tv::volup()
{
if(volume
{
volume++;
return true;
}
else
return false;
}
bool Tv::voldown()
{
if(volume>MinVal)
{
volume--;
return true;
}
else
return false;
}
void Tv::chanup()
{
if(channel
channel++;
else
channel=1;
}
void Tv::chandown()
{
if(channel>1)
channel--;
else
channel=maxchannel;
}
void Tv::settings()const
{
std::cout<<"TV is "<<(state==Off? "Off":"On")<<std::endl;
if(state==On)
{
std::cout<<"Volume setting="<<volume<<std::endl;
std::cout<<"Channel setting="<<channel<<std::endl;
std::cout<<"Mode="<<(mode==Antenna? "antenna" : "cable")<<std::endl;
std::cout<<"Input="<<(input==TV? "TV":"DVD")<<std::endl;
}
}

#include
#include"151.h"
using namespace std;
bool Tv::volup()
{
if(volume
{
volume++;
return true;
}
else
return false;
}
bool Tv::voldown()
{
if(volume>MinVal)
{
volume--;
return true;
}
else
return false;
}
void Tv::chanup()
{
if(channel
channel++;
else
channel=1;
}
void Tv::chandown()
{
if(channel>1)
channel--;
else
channel=maxchannel;
}
void Tv::settings()const
{
cout<<"TV is "<<(state==Off? "Off":"On")<<endl;
if(state==On)
{
cout<<"Volume setting="<<volume<<endl;
cout<<"Channel setting="<<channel<<endl;
cout<<"Mode="<<(mode==Antenna? "antenna" : "cable")<<endl;
cout<<"Input="<<(input==TV? "TV":"DVD")<<endl;
}
}

解决方案

代码贴的不完整，最好把完整代码贴出来，inline void Tv::ch_h(Remote &t)，这个Tv类利用Remote类，这个你上前声明了Remote类么？

inline void Tv::ch_h(Remote &t)
{
if(t.style==Remote::hudong)
t.style=Remote::changgui;
else t.style=Remote::hudong;
}
Tv类是Remote类的友元类，但Remote类并不是Tv类的友元类，总之代码不完整，不好看