实验四 继承

实验二源码：

#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);
}

运行结果截图：

 加上virtual后：

归纳总结：

同名覆盖原则：派生类与基类中有相同成员时，通过派生类对象使用的是派生类的同名成员；

二元作用域分辨符：类名称::成员名，可以精确指定某个成员；

类型兼容原则：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：

　　　　(1)派生类对象可以隐含转化为基类对象，b1=d1;

　　　　(2)派生类的对象可以初始化基类的引用，B &rb=d1；

　　　　(3)派生类的指针可以隐含转化为基类的指针，pb1=&d1;

 

实验三：

 

Battery.hpp源码：

#ifndef BATTERY_HPP
#define BATTERY_HPP

#include<iostream>

using namespace std;

class Battery
{
private:
    int capacity;
public:
    Battery(int capacity0=70):capacity(capacity0){}
    ~Battery();
    int get_capacity();
};

Battery::~Battery()
{
}

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

#endif

Car.hpp源码：

#ifndef CAR_HPP
#define CAR_HPP

#include<iostream>
#include<string>

using namespace std;

class Car
{
protected:
    string maker,model;
    int year,odometers;
public:
    Car(string maker0,string model0,int year0,int odometers0=0):maker(maker0),model(model0),year(year0),odometers(odometers0){}
    ~Car()=default;
    void info();
    void update_odometers(int update);
};

void Car::info()
{
    cout<<"maker:          "<<maker<<endl;
    cout<<"model:          "<<model<<endl;
    cout<<"year:           "<<year<<endl;
    cout<<"odometers:      "<<odometers<<endl;
}

void Car::update_odometers(int update)
{
    if(update<odometers) cout<<"wrong updating information...";
    else odometers=update;
}

#endif

ElectricCar.hpp源码：

#ifndef ELECTRICCAR_HPP
#define ELECTRICCAR_HPP

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

class ElectricCar : public Car
{
private:
    Battery battery;
public:
    ElectricCar(string maker0,string model0,int year0,int odometers0=0,Battery battery0=70):Car(maker0,model0,year0,odometers0),battery(battery0){}
    ~ElectricCar()=default;
    void info();
};

void ElectricCar::info()
{
    Car::info();
    cout<<"capacity:       "<<battery.get_capacity()<<"-kWh"<<endl;
}
#endif

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();
}

运行结果截图：

 

 

实验四：

 pets.hpp源码：

#ifndef PESTS_HPP
#define PETS_HPP
#include<iostream>
#include<string>

using std::cin;
using std::cout;
using std::string;

class MachinePets
{
protected:
    string nickname;
public:
    MachinePets(const string s):nickname(s){}
    string get_nickname()const {return nickname;}
    virtual string talk(){return "haha";} 
    ~MachinePets()=default;
};

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);
}