实验四 继承

实验任务2

实验源码

 

#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);
}

 

不加virtual

 

 加virtual

 

 同名覆盖原则：在派生类中定义了和基类相同的函数，那么派生类会覆盖基类的函数。

二元作用域分辨符：为了访问基类同名成员。

类型兼容原则：在需要基类对象的任何地方，都可以使用公有派生类的对象来替代。

 

实验任务3

battery.h

#ifndef BATTERY_H
#define BATTERY_H
#include<iostream>
using namespace std;
class Battery{
    public:
        Battery(int a=70):capacity{a}{};
        void get_capacity();
    private:
        int capacity;
};
void Battery::get_capacity()
{
    cout<<capacity<<"-kwh"<<endl;
}
#endif

car.h

#ifndef CAR_H
#define CAR_H
#include<iostream>
using namespace std;
class Car{
    public:
        Car(string a,string b,int c):maker{a},model{b},year{c}{odometers=0;};
        void info();
        void update_odometers(int m);
    protected:
        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;
}
void Car::update_odometers(int m)
{
    if(m<odometers) cout<<"wrong odometer"<<endl;
    else
    {
        odometers=m;
        cout<<"update success"<<endl;
    }
}
#endif

electricCar.h

#ifndef ELECTRICCAR_H
#define ELECTRICCAR_H
#include<iostream>
#include"car.h"
#include"battery.h"
using namespace std;
class ElectricCar:public Car{
    public:
        ElectricCar(string a,string b,int c):Car{a,b,c}{};
        void info();
    protected:
        Battery battery;
};
void ElectricCar::info()
{
    cout<<"maker:"<<maker<<endl;
    cout<<"model:"<<model<<endl;
    cout<<"year:"<<year<<endl;
    cout<<"odometers:"<<odometers<<endl;
    cout<<"capacity:";
    battery.get_capacity();
}
#endif

task3.cpp

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

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();
}

运行截图

 

 

 更换测试数据

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

int main()
{
    using namespace std;

    // test class of Car
    Car oldcar("BYD", "newbrand", 2020);
    cout << "--------oldcar's info--------" << endl;
    oldcar.update_odometers(15);
    oldcar.info();

    cout << endl;

    // test class of ElectricCar
    ElectricCar newcar("Tesla", "model x", 2021);
    newcar.update_odometers(15);
    cout << "\n--------newcar's info--------\n";
    newcar.info();
}

 

 

 

 实验任务四

 pets.h

 

#ifndef PETS_H
#define PETS_H
#include<iostream>
using namespace std;
class MachinePets {
public:
    MachinePets(const string s) :nickname{ s } {}
    virtual string talk() { return "123"; }
    const string get_nickname()
    {
        return nickname;
    }
protected:
    string nickname;
};
class PetCats :virtual public MachinePets {
public:
    PetCats(const string s) :MachinePets{ s } {}
    string talk()
    {
        return "miao wu~";
    }
};
class PetDogs :virtual public MachinePets {
public:
    PetDogs(const string s) :MachinePets{ s } {}
    string talk()
    {
        return "wang wang~";
    }
};
#endif

 

task4.cpp

#include <iostream>
#include "pets.h"

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);
}

 实验截图