C++中虚函数的使用实例

/******************mystr.h***********/
#include<string.h>
#include<iostream>

//using namespace std;
using std::cin;
using std::cout;
using std::endl;

class Mystring{

    char *str;

public:
    Mystring(char *string){
        str=new char[strlen(string)+1];
        strcpy(str,string);
    }
    Mystring(const Mystring &p){

        str=new char[strlen(p.str)+1];
        strcpy(str,p.str);
    }
    ~Mystring(){ delete str;}

    Mystring& operator = (const Mystring &str3){
        delete this->str;
        this->str = new char[strlen(str3.str)+1];
        strcpy(this->str,str3.str);
        return *this;
    }
    friend char* operator + (Mystring&,Mystring&);

    char index(int i);
    int length(void);
    bool replace(int i,char ch);
    bool remove(int i);
    char* display();
};

char Mystring::index(int i)
{
    return *(str+i-1);
}

int Mystring::length(void)
{
    int i=0;
    while(*(str+i) != '\0')
        i++;
    return i;
}

bool Mystring::replace(int i,char ch)
{
    *(str+i-1) = ch;
    return true;
}

bool Mystring::remove(int i)
{
    memset(str+i,0,strlen(str)-i);
    return true;
}

char* Mystring::display()
{
    return this->str;
}

char* operator +(Mystring& str1,Mystring& str2)
{
    char *p;
    p = new char[strlen(str1.str)+strlen(str2.str)+2];
    strcpy(p,str1.str);
    strcat(p,str2.str);

    return p;
}


/**************animal.h*************/
#include "mystr.h"

class animal{

    Mystring name;

public:
    animal(char *ch):name(ch)
    {
        //cout<<"animal构造"<<endl;
    }
    ~animal() {}
    virtual void sleep();
    virtual void eat();
    virtual void play();
    char* display();
};

void animal::sleep()
{
    cout<<this->name.display()<<"is sleeping...."<<endl;
}

void animal::eat()
{
    cout<<this->name.display()<<"is eating...."<<endl;
}

void animal::play()
{
    cout<<this->name.display()<<"is playing...."<<endl;
}

char* animal::display()
{
    return name.display();
}

/**************cat.h*************/
#include "animal.h"

class cat:public animal{

public:
    cat(char *name_cat):animal(name_cat)
    {
        cout<<"Hello,I am "<<cat::display()<<endl;
    }
    ~cat() {}
    void sleep();
    void eat();
    void play();
};

void cat::sleep()
{
    cout<<"cat "<<cat::display()<<" is sleeping..."<<endl;
}

void cat::eat()
{
    cout<<"cat "<<cat::display()<<" is eating..."<<endl;
}

void cat::play()
{
    cout<<"cat "<<cat::display()<<" is playing..."<<endl;
}


class dog:public animal{

public:
    dog(char *name_dog):animal(name_dog)
    {
        cout<<"Hello,I am "<<dog::display()<<endl;
    }
    ~dog() {}
    void sleep();
    void eat();
    void play();
};

void dog::sleep()
{
    cout<<"dog "<<dog::display()<<" is sleeping..."<<endl;
}

void dog::eat()
{
    cout<<"dog "<<dog::display()<<" is eating..."<<endl;
}

void dog::play()
{
    cout<<"dog "<<dog::display()<<" is playing..."<<endl;
}

/*************human.h****************/
#include "cat.h"

class human:public animal{

    int age;

public:
    human(char *name_human,int age):animal(name_human)
    {
        this->age = age;
        cout<<"Hello,I am "<<human::display()<<endl;
    }
    ~human() {}

    void play_with(animal&);

};

void human::play_with(animal &p)
{
    cout<<human::display()<<" is play with "<<p.display()<<endl;
    p.play();
}

#include "human.h"

int main()
{
    cat cat1("congcong");
    dog dog1("huanhuan");

    human boy("hanhan",25);
    boy.play_with(cat1);
    boy.play_with(dog1);

    return 0;
}