实验4 继承

task2.cpp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);
}

源代码对应实验结果：

 task2.cpp修改后源码

#include <iostream>
#include <typeinfo>

// definitation of Graph
class Graph
{
public:
    virtual 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);
}

task2.cpp修改后的实验结果截图：

 task2的归纳总结

同名覆盖原则：覆盖是指派生类重新实现（或者改写）了基类的成员函数,其特征如下：1.不同的作用域（分别位于派生类和基类中）；2.函数名称相同；3.参数列表完全相同；4.基类函数必须是虚函数。满足这四个条件之后，派生类的对象使用函数时会进行派生类中的代码规则运行。

二元作用域分辨符：即不论是否派用类还是基类，同名函数前对应的类名是什么，对应的代码运行规则便是该类名内的规则。

类型兼容原则：1.派生类的对象可以隐含转换为基类对象；2.派生类的对象可以初始化基类的引用；3.派生类的指针可以隐含转换为基类的指针

task3.cpp源码

#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();
}

task3.cpp修改后源码

#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("Porsche", "911", 2020);
    newcar.update_odometers(5200);
    cout << "\n--------newcar's info--------\n";
    newcar.info();
}

battery.hpp源码

#include<iostream>

using namespace std;

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

car.hpp源码

#include<iostream>
#include<string>

using namespace std;

class Car{
    public:
    Car(string n_maker,string n_model,int n_year):maker(n_maker),model(n_model),year(n_year),odometers(0){}
    virtual void info(){
        cout<<"maker:          "<<maker<<endl;
        cout<<"model:          "<<model<<endl;
        cout<<"year:           "<<year<<endl;
        cout<<"odometers:      "<<odometers<<endl;
    }
    void update_odometers(float n_odometers){
        if(n_odometers<odometers) cout<<"the odometer you want to update is wrong."<<endl;
        else odometers=n_odometers;
    }
    private:
    string maker;
    string model;
    int year;
    float odometers;
};

electricCar.hpp源码

#include<iostream>
#include"battery.hpp"
#include"car.hpp"

using namespace std;

class ElectricCar:public Car
{
    public:
    ElectricCar(string n_maker,string n_model,int n_year):Car(n_maker,n_model,n_year){}
    void info(){
        Car::info();
        cout<<"battery:        "<<battery.get_capacity()<<"-kwh"<<endl;
    }
    private:
    Battery battery;
};

task3实验结果截图

task3修改后实验结果截图

task4.cpp源码

#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源码

#include<iostream>
#include<string>

using namespace std;

class MachinePets{
    public:
    MachinePets(const string n_nickname):nickname(n_nickname){}
    virtual string talk(){
        return "i love u";
    }
    string get_nickname(){
        return nickname;
    }
    private:
    string nickname;
};

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

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

task4实验结果截图