C++primer plus第六版课后编程题答案15.1

tv.h

#ifndef TV_h_
#define TV_h_
#include <iostream>
using namespace std;
class Remote;
class Tv{
private:
int state;
int volume;
int maxchannel;
int channel;
int mode;
int input;
public:
friend class Remote;
enum{Off,On};
enum {MinVal,MaxVal=20};
enum{Antenna,Cable};
enum {TV,DVD};

Tv(int s=Off,int mc=125):state(s),volume(5),maxchannel(mc),channel(2),mode(Cable),input(TV){};
void onoff(){
state=(state==On)?Off:On;
};
bool ison(){
return state==On;
};
bool volup();
bool voldown();
void chanup();
void chandown();
void set_mode(){
mode=(mode==Antenna)?Cable:Antenna;
};
void set_input(){

input=(input==TV)?DVD:TV; //这是个什么情况？？？
};
void setting()const;
void setR(Remote &r);//这里不能有方法的定义，否则会导致前置声明的混乱而无法编译

};
class Remote
{
friend class Tv;
private:
int mode;
int RemoteMode;//用于描述遥控器的模式
enum{RemoteOn,RemoteOff};
public:
Remote(int m=Tv::TV,int rm=RemoteOn):mode(m){};//构造函数多了一个
bool volup(Tv &t){return t.volup();};
bool vodown(Tv &t){ return t.voldown();};
void onoff(Tv &t){return 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();};
void show()
{
cout<<"RemoteMode:"<<(RemoteMode==RemoteOn?"RemoteOn":"RemoteOff")<<endl;
}
void change()
{
RemoteMode=RemoteOn?RemoteOff:RemoteOn;//用于Tv类切换
}
};
#endif

tv.cpp
#include "tv.h"
#include <iostream>
using namespace std;

//tv
bool Tv::volup()
{
if(volume<MaxVal)
{
volume++;
return true;
}
else
return false;
}

bool Tv::voldown()
{
if(volume>MinVal)
{
volume--;
return true;
}
else
return false;
}

void Tv::chanup()
{
if(channel<maxchannel)
channel++;
else
channel=1;
}
void Tv::chandown()
{
if(channel>1)
channel--;
else
channel=maxchannel;
}

void Tv::setting()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;
}
}
void Tv::setR(Remote &r)
{
if(state==On)
r.change();
else
cout<<"Tv is not on!"<<endl;
}


main151.cpp
#include "tv.h"
#include <iostream>
using namespace std;

void main151()
{
/*
Tv t;
cout<<"Initial setting for t"<<endl;
t.setting();
t.onoff();
t.chanup();
cout<<"\nAdjusted settings for t"<<endl;
t.setting();
t.chanup();
cout<<"Adjusted setting for t"<<endl;
t.setting();
*/
Remote grey;
/*
grey.set_chan(t,10);
grey.volup(t);
grey.volup(t);
cout<<"t \"settings after using remote:"<<endl;
t.setting();
*/
Tv t11(Tv::On);
t11.setting();
grey.set_chan(t11,28);
cout<<"t11 settings "<<endl;
t11.setting();

grey.show();
t11.setR(grey);
grey.show();

}