实验4 继承

实验任务2（验证性实验）

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

 如果一个类有直接或间接的虚基类，则先执行虚基类的构造函数

如果该类有其他基类，则按照它们在继承声明列表中的出现的次序，分别执行它们的构造函数，但构造过程中，不再执行它们的虚基类的构造函数

 

 

对代码微调后，运行结果截图：

 

 实验任务3

程序源码：

//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();
}

//electricCar.hpp
#pragma once
#include<iostream>
#include"car.hpp"
#include"battery.hpp"
using namespace std;
class ElectricCar :public Car
{
public:
    ElectricCar(string maker0, string model0, int year0) :Car(maker0, model0, year0), battery() {}
    void info()
    {
        cout << left << setw(20) << "maker:" << maker << endl;
        cout << left << setw(20) << "model:" << model << endl;
        cout << left << setw(20) << "year:" << year << endl;
        cout << left << setw(20) << "odometers:" << odometers << endl;
        cout << left << setw(20) << "capacity:" << battery.get_capacity() << "-kwh" << endl;
    }
private:
    Battery battery;
};

//battery.hpp
#pragma once
#include<iostream>
class Battery
{
public:
    Battery() :capacity(70) {}
    int get_capacity() { return capacity; }
protected:
    double capacity;
};

//car.hpp
#pragma once
#include<iostream>
#include<iomanip>
using std::cout;
using std::cin;
using std::endl;
using std::string;
using std::setw;
using std::left;
class Car
{
public:
    Car(string maker0,string model0,int year0):maker(maker0),model(model0),year(year0),odometers(0) {}
    void info()
    {
        cout << left << setw(20) << "maker:" << maker << endl;
        cout << left << setw(20) << "model:" << model << endl;
        cout << left << setw(20) << "year:" << year << endl;
        cout << left << setw(20) << "odometers:" << odometers << endl;
    }
    void update_odometers(int n)
    {
        int temp = odometers; 
        odometers = n;
        if (odometers < temp)
            cout << "warning,输入数据有误!" << endl;
    }
    string maker;
    string model;
    int year;
    int odometers;
};

运行结果截图（更换数据后）：

 实验任务4

//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);
}

//pets.hpp
#pragma once
#include<iostream>
#include<string>
using namespace std;
class MachinePets
{
public:
    MachinePets(const string s) :nickname(s) {}
    string get_nickname()const
    {
        return nickname;
    }
    string virtual talk() { return "voice"; }
    string nickname;
};
class PetCats:public MachinePets
{
public:
    PetCats(const string s) :MachinePets(s) {}
    inline string talk()
    {
        return "miao wu~";
    }
};
class PetDogs :public MachinePets
{
public:
    PetDogs(const string s) :MachinePets(s) {}
    inline string talk()
    {
        return "wang wang~";
    }
};

运行测试截图：（未更改）