实验任务二:

(原代码)

#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:

总结:

1、同名覆盖原则:派生类中新增的成员具有更小的类作用域,因此,在派生类及建立派生类对象的模块中,派生类新增成员隐藏了基类的同名成员。

2、二元作用域分辨符:可以用来限定要访问的成员所在的类的名称。

3、类型兼容规则: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。

(改进后代码)

#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);
}

运行结果:

 与原来的不同在于:

运行时指针变量ptr实际指向的对象的类型信息发生了改变。
实验任务3:
(task3.cpp代码)
#include <iostream>
#include <string>
#include "battery.hpp"
#include "car.hpp"
#include "electricCar.hpp"
using namespace std;

int main()
{
    using namespace std;

    // test class of Car
    Car oldcar("Audi", "a4", 2020);
    cout << "--------oldcar's info--------" << endl;
    oldcar.update_odometers(25000);
    oldcar.info();

    cout << endl;

    // test class of ElectricCar
    ElectricCar newcar("Tesla", "model s", 2020);
    newcar.update_odometers(5000);
    cout << "\n--------newcar's info--------\n";
    newcar.info();
}

(battery.hpp代码)

#pragma once
#include <iostream>
#include <string>
using namespace std;

class Battery
{
public:
    Battery(int ca = 70) : capacity(ca) {}

    void get_capacity()
    {
        cout << "capacity:\t" << capacity << "-kwh" << endl;
    }

    ~Battery() = default;
private:
    int capacity;
};

(car.hpp代码)

#pragma once
#include <iostream>
#include <string>
using namespace std;

class Car
{
public:
    Car() = default;
    Car(string ma, string mo, int ye, int od = 0) : maker(ma), model(mo), year(ye), odometers(od) {}
    void info()
    {
        cout << "maker:\t" << maker << endl;
        cout << "model:\t" << model << endl;
        cout << "year:\t" << year << endl;
        cout << "odometers:\t" << odometers << endl;
    }
    void update_odometers(int newod)
    {
        if (newod < 0)
            cout << "更新数值有误\n";
        else
            odometers += newod;
    }
    ~Car() = default;
public:
    string maker;
    string model;
    int year;
    int odometers;
};

(electricCar.hpp代码)

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

class ElectricCar : public Car
{
public:
    ElectricCar(string ma, string mo, int ye, int od = 0, int ca = 70);

    void info();

    ~ElectricCar() = default;

private:
    Battery battery;
};
ElectricCar::ElectricCar(string ma, string mo, int ye, int od = 0, int ca = 70) : battery(ca)
{
    maker = ma;
    model = mo;
    year = ye;
    odometers = od;
}

void ElectricCar::info()
{
    cout << "maker:\t" << maker << endl;
    cout << "model:\t" << model << endl;
    cout << "year:\t" << year << endl;
    cout << "odometers:\t" << odometers << endl;
    battery.get_capacity();
}

运行结果:

 实验任务4:

(task4.cpp)

#include <iostream>
#include <string>
#include "pets.hpp"
using namespace std;

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)

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

class MachinePets
{
public:
    string nickname;
public:
    MachinePets() = default;
    MachinePets(const string s);
    virtual string talk() = 0;
    const string get_nickname()
    {
        return nickname;
    }
};
MachinePets::MachinePets(const string s) : nickname(s) {}

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

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

运行结果:

 总结:

1、通过这次实验我对类的继承的了解更加深刻了;

2、不过,对于继承和组合还是存在一丝理解的模糊;

posted on 2021-11-26 14:04  Giant邹薛成  阅读(44)  评论(3编辑  收藏  举报