实验四

task2

程序源码

#include <iostream>
#include <typeinfo>

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


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


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


// definitaion 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 operator::
    r1.Graph::draw();
    c1.Graph::draw();

    std::cout << "\n";

    // call by pointer to Base class
    fun(&g1);
    fun(&r1);
    fun(&c1);
}

运行结果截图

 归纳总结

同名覆盖原则：若派生类和基类中有同名的成员，派生类将覆盖基类的函数

二元作用域分辨符：通过使用继承类：：函数来访问基类中被派生类覆盖的同名函数

类型兼容原则：基类对象可以使用共有派生类的对象代替

微调后运行结果截图：

 

 task 3

battery.hpp

#include <iostream>
using namespace std;
class Battery{
    private:
        int capacity;
        
    public:
         Battery(int capacity0=70):capacity(capacity0){}
         int get_capacity(){return capacity;}         

};

car.hpp

#include <iostream>
#include <string>
#include <iomanip>
using namespace std;

class Car{
            
    public:
        Car(const string maker0,const string model0,int year0,int odometers0=0):maker(maker0),model(model0),year(year0),odometers(odometers0){}
        void info();
        void update_odometers(int new_odometers);
    
    private:
        string maker;
        string model;
        int year;
        int odometers;
};

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

void Car::update_odometers(int new_odometers)
{
    if(new_odometers<odometers)
        cout<<"INCORRECT UPDATA VALUE"<<endl;
    else odometers=new_odometers;
}

electricCar.hpp

#include <iostream>
#include <string>
#include <iomanip>
#include "car.hpp"
#include "battery.hpp"
using namespace std;

class ElectricCar:public Car{
    private:
        Battery battery;
    
    public:
        ElectricCar(const string maker0,const string model0,int year0,int odometers0=0,int capacity0=70):Car(maker0,model0,year0),battery(capacity0){}
        void info();
};

void ElectricCar::info()
{
    Car::info();
    battery.get_capacity();
}

task3.cpp

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

int main()
{
    using namespace std;

    // test class of Car
    Car oldcar("Audi", "a4", 2016);
    cout << "--------oldcar's info--------" << endl;
    oldcar.update_odometers(25000);
    oldcar.info();

    cout << endl;

    // test class of ElectricCar
    ElectricCar newcar("Tesla", "model s", 2016);
    newcar.update_odometers(2500);
    cout << "\n--------newcar's info--------\n";
    newcar.info();
}

 task4

pets.hpp

#include <iostream>
#include <string>
#include <iomanip>
using namespace std;

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

class PetCats:public MachinePets
{
    public:
        PetCats(const string s):MachinePets(s){}
        virtual string talk()
        {
            return "miao wu~";
        }
        
};

class PetDogs:public MachinePets
{
    public:
        PetDogs(const string s):MachinePets(s){}
        virtual string talk()
        {
            return "wang wang~";
        }
        
};

task4.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);
}