实验四 继承

任务二

task2：

#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);
}

测试截图：

 

 微调代码后：

#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);
}

测试截图

 

归纳总结：

同名覆盖原则：

派生类与基类中有相同成员时：
若未强行指名，则通过派生类对象使用的是派生类的同名成员；

二元作用域分辨域：

::作二元作用域分辨符的用法是：类名::成员 

类型兼容原则：

1.派生类的对象可以隐含转换为基类的对象。
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化为基类的指针。

在替代之后，派生类的对象就可以作为基类的对象使用，但只能使用从基类继承

 任务三
Battary.hpp

#ifndef BATTARY_HPP
#define BATTARY_HPP
using namespace std;
class Battary
{
    public:
    Battary(int c0 = 70):capacity(c0){};
    ~Battary(){};
    int get_capacity(){return capacity;};
    private:
    int capacity;
};
#endif

Car.hpp

#ifndef CAR_HPP
#define CAR_HPP
#include <iostream>
#include <string>
#include <iomanip>
using namespace std;
class Car
{
    public:
    Car(string m1,string m2,int y,int o = 0):maker{m1},model{m2},year{y},odometers{o}{};
    ~Car(){};
    virtual void info();
    void update_odometers(int o1);
    private:
    string maker;
    string model;
    int year;
    int odometers;
};
void Car::info()
{
    cout<<"maker:        "<<setiosflags(ios::left)<<setw(10)<<maker<<endl;
    cout<<"model:        "<<setw(10)<<model<<endl;
    cout<<"year:         "<<setw(10)<<year<<endl;
    cout<<"odometers:    "<<setw(10)<<odometers<<endl;
}
void Car::update_odometers(int o1)
{
    if(o1<odometers)
    cout<<"Error!!!!";
    else 
    odometers = o1;
}
#endif

ElectricCar.hpp

#ifndef ELECTRICAR_HPP
#define ELECTRICAR_HPP
#include <iostream>
#include <string>
#include <iomanip>
#include "Car.hpp"
#include "Battary.hpp"
using namespace std;
class ElectricCar:public Car 
{
    public:
    ElectricCar(string m1,string m2,int y,Battary b = 70):Car(m1,m2,y,0),battary(b){};
    void info();
    private:
    Battary battary;
};
void ElectricCar::info()
{
    Car::info();
    cout << "capacity:     "<<battary.get_capacity()<<"-kWh"<<endl;
}
#endif

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();
}

运行测试截图

 

 task4

Pets.hpp

 

 

#ifndef PETS_HPP
#define PETS_HPP
#include <string>
using namespace std;
class MachinePets
{
public:
    MachinePets(const string s):nickname(s){};
    string get_nickname() const { return nickname; };
    virtual string talk(){return "hhhhhhh";};
private:
    string nickname;
};
class PetCats:public MachinePets
{
    public:
    PetCats(const string s):MachinePets(s){};
    string talk(){return "miao!";};
};
class PetDogs:public MachinePets
{
    public:
    PetDogs(const string s):MachinePets(s){};
    string talk(){return "wang!!";};
};
#endif

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);
}

运行截图：