实验4 继承

tsak2.cpp文件源码

#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);
}

原测试截图：

修改后测试截图：

归纳总结：

(1)公有派生类的对象可以用来在需要基类的对象的地方替代使用，但替代之后只能使用从基类继承的成员。

(2)对于同名的成员，访问派生类或基类的同名成员时，需加作用域符，即 对象名.类名：：成员名，否则以 对象名.成员名 的形式访问的是派生类的同名成员。

(3)在多重继承下，为了访问基类或派生类中同名成员，需要定义虚基类。

---

car.hpp源代码

#ifndef Car_hpp
#define Car_hpp
#include <iostream>
using namespace std;

class Car {
public:
    Car(string maker0, string model0, int year0, int odometers0 = 0) :maker(maker0), model(model0), year(year0), odometers(odometers0) {}
    void info()
    {
        cout << "maker: \t\t\t" << maker << endl;
        cout << "model: \t\t\t" << model << endl;
        cout << "year: \t\t\t" << year << endl;
        cout << "odeometers: \t\t" << odometers << endl;
    }
    void update_odometers(int odometers0)
    {
        if (odometers0 < odometers)
        {
            cout << endl;
            cout << "更新数值有误!!!" << endl;
            cout << endl;
        }
        else
            odometers = odometers0;
    }
private:
    string maker;
    string model;
    int year;
    int odometers;
};

#endif

electricCar.hpp源代码

#ifndef ElectricCar_hpp
#define ElectricCar_hpp
#include "Car.hpp"
#include "Battery.hpp"
#include <iostream>
using namespace std;

class ElectricCar :public Car {
public:
    ElectricCar(string E_maker, string E_model, int E_year) :Car(E_maker, E_model, E_year), battery(70) {}
    void info()
    {
        Car::info();//调用基类函数info输出前四项
        cout << "capacity: \t\t" << battery.get_capacity() << "-kwh" << endl;
    }
private:
    Battery battery;
};

#endif

battery.hpp源代码

#ifndef Battery_hpp
#define Battery_hpp
#include <iostream>
using namespace std;

class Battery {
public:
    Battery():capacity(70) {};//默认构造函数
    Battery(int capacity0) :capacity(capacity0) {}

    int get_capacity()
    {
        return capacity;
    }
private:
    int capacity;
};

#endif

task3.cpp源代码

#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();
}

测试截图：

---

pets.hpp源代码

#ifndef pets_hpp
#define pets_hpp
#include<iostream>
using namespace std;
class MachinePets {
public:
    MachinePets(const string s) :nickname(s) {}
    virtual string talk() { return "^^"; }

    string get_nickname() const
    {
        return nickname;
    }

private:
    string nickname;
};

class PetCats :public MachinePets {
public:
    PetCats(const string s) :MachinePets(s) {}

    string talk()
    {
        return "miao wu~";
    }
};

class PetDogs :public MachinePets {
public:
    PetDogs(const string s) :MachinePets(s) {}

    string talk()
    {
        return "wang wang~";
    }
};
#endif

task4.cpp源代码

#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);
}

测试截图：