实验四

task 2 改动后

#include<iostream>
#include<typeinfo>

//definition of Graph
class Graph
{
    public:
        void draw(){ std::cout<<"Graph::draw() : just as an interface\n";}        
};


//definition of Rectangle, derived fron graph
class Rectangle : public Graph
{
    public:
        void draw() { std::cout<<"Rectangle::draw(): programs of draw a rectangl\n";}
};


//definition of ciecle, derived from Graph
class Circle : public Graph
{
    public: 
         virtual  void draw(){std:: cout<<"Circle::draw(): programs of draw a cicle\n";}
};


//definition of fun(): as a call interface
void fun(Graph *ptr)
{
    std::cout<<"pointer type: "<<typeid(ptr).name()<<"\n";
    std::cout<<"RTTI type: "<<typeid(*ptr).name()<<"\n";
    ptr->draw();
 } 
 
 //test
int main()
{
    Graph g1;
    Rectangle r1;
    Circle c1;
    
       //call by object name
       g1.draw();
       r1.draw();
       c1.draw();
       
       std::cout << "\n";
       
       //call by object name,and using the scope resolution opertor::
       r1.Graph::draw();
       c1.Graph::draw();
       
       std::cout<<"\n";
       
       //call by pointer to Base class
       fun(&g1);
       fun(&r1);
       fun(&c1);
}

改动前截图：

 

改动后截图：

1. 同名覆盖原则：派生类与基类有相同成员时，若未强行指名，则通过派生类对象使用的是派生类的同名成员；

2.二元作用域分辨符：

当派生类新增成员隐藏了基类的同名成员，这时使用“对象名.成员名”的访问方式只能访问到派生类新增成员。对基类同名成员的访问，只能通过基类名哥作用域分辨符来实现

Car.hpp

#ifndef Car_hpp
#define Car_hpp
#include<iostream>
#include<string>
using namespace std;

class Car
{
    private:
        string maker;
        string model;
        int year;
        int odometers;
    public:
        Car(string maker1, string model1, int year1, int odometers1=0): maker(maker1), model(model1), year(year1), odometers(odometers1) { };
        void info();
        void update_odometers(int new_odometers);
};

void Car::info(){
    cout<<"maker:\t\t"<<maker<<endl;
    cout<<"model:\t\t"<<model<<endl;
    cout<<"year:\t\t"<<year<<endl;
    cout<<"odometers:\t"<<odometers<<endl;
}

void Car::update_odometers(int new_odometers){
    if(new_odometers<odometers)
    cout<<"更新数值有误"<<endl;
    else
    odometers=new_odometers; 
}

#endif

Battery.hpp

#ifndef Battery_hpp
#define Battery_hpp
#include<iostream>
using namespace std;

class Battery{
    private:
        int capacity;
    public:
        Battery(int capa=70): capacity(capa){
        };
        int get_capacity(){
            return capacity;
        }
};

#endif

ElectricCar.hpp

#ifndef ElectricCar_hpp
#define ElectricCar_hpp
#include<iostream>
#include<string>
#include"Car.hpp"
#include"Battery.hpp"
using namespace std;

class ElectricCar: public Car{
    private:
        Battery battery;
    public:
     ElectricCar(string ma, string mo, int y, int c=70): Car(ma, mo, y), battery(c) {
     };
     void info();
     ~ElectricCar(){};
    
};

void ElectricCar::info(){
    Car::info();
    cout<<"capacity:\t"<<battery.get_capacity()<<"-kwh"<<endl;
}

#endif

task3.cpp

#include<iostream>
#include"ElectricCar.hpp"

int main()
{
    using namespace std;
    
    //test class of Car
    Car oldcar("lisa","c7",2102);
    cout<<"--------oldcar's info----------"<<endl;
    oldcar.update_odometers(50000);
    oldcar.info();
    
    cout<<endl;
    
    //test class of ElectricCar
    ElectricCar newcar("Ta","models",1032);
    newcar.update_odometers(8273);
    cout<<"\n----------newcar's info--------------\n";
    newcar.info();
}

运行截图

 Pets.hpp

#ifndef Pets_hpp
#define Pets_hpp
#include<iostream>
#include<string>
using namespace std;

class MachinePets{
    private:
        string nickname;
    public:
       MachinePets(const string nickname1): nickname(nickname1){
       }
      string get_nickname() const;
      virtual string talk();        
};

string MachinePets::get_nickname() const{
       return nickname;
}

string MachinePets::talk(){
    return "hahahha";
}

class PetCats: public MachinePets
{
    private:
        string nickname;
    public:
        PetCats(const string nickname1): MachinePets(nickname1){}
        string talk()
        {
            return "miao~wu~";
        }
};

class PetDogs: public MachinePets
{
    private:
        string nickname;
    public:
        PetDogs(const string nickname1): MachinePets(nickname1){
        }
        string talk()
        {
            return "wang ~wang ~";
        }
};

#endif

task 4.cpp

#include <iostream>
#include "Pets.hpp"
void play(MachinePets *ptr)
{
    std::cout << ptr->get_nickname() << " says " << ptr->talk() <<std::endl;
}
int main()
{
    PetCats cat("miku");
    PetDogs dog("da huang");
    
    play(&cat);
    play(&dog);
}