tvfm.h

一本很好的C++学习的丛书！初学者必看的

// tvfm.h -- Tv and Remote classes using a friend member
#ifndef TVFM_H_
#define TVFM_H_

class Tv;                       // forward declaration

class Remote
{
public:
    enum State{Off, On};
    enum {MinVal,MaxVal = 20};
    enum {Antenna, Cable};
    enum {TV, VCR};
private:
    int mode;
public:
    Remote(int m = TV) : mode(m) {}
    bool volup(Tv & t);         // prototype only
    bool voldown(Tv & t);
    void onoff(Tv & t) ;
    void chanup(Tv & t) ;
    void chandown(Tv & t) ;
    void set_mode(Tv & t) ;
    void set_input(Tv & t);
    void set_chan(Tv & t, int c);

};

class Tv
{
public:
    friend void Remote::set_chan(Tv & t, int c);
    enum State{Off, On};
    enum {MinVal,MaxVal = 20};
    enum {Antenna, Cable};
    enum {TV, VCR};

    Tv(int s = Off, int mc = 100) : state(s), volume(5),
        maxchannel(mc), channel(2), mode(Cable), input(TV) {}
    void onoff() {state = (state == On)? Off : On;}
    bool ison() const {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)? VCR : TV;}
    void settings() const;
private:
    int state;
    int volume;
    int maxchannel;
    int channel;
    int mode;
    int input;
};

// Remote methods as inline functions
inline bool Remote::volup(Tv & t) { return t.volup();}
inline bool Remote::voldown(Tv & t) { return t.voldown();}
inline void Remote::onoff(Tv & t) { t.onoff(); }
inline void Remote::chanup(Tv & t) {t.chanup();}
inline void Remote::chandown(Tv & t) {t.chandown();}
inline void Remote::set_mode(Tv & t) {t.set_mode();}
inline void Remote::set_input(Tv & t) {t.set_input();}
inline void Remote::set_chan(Tv & t, int c) {t.channel = c;} 

#endif