实验4 继承

实验任务2

#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);
}

 

 

同名覆盖原则：派生类和继承类函数完全相同时，通过派生类对象只访问派生类中的函数。

二元作用域分辨符：可以指定想要访问某个类的函数。

类型兼容原则：派生类对象可以作为基类的对象使用。

实验任务3

battery.hpp

#ifndef BATTERY_HPP
#define BATTERY_HPP
#include<iostream>
using namespace std;
class Battery{
    public:
        Battery(int c=70):capacity(c){}
        int get_capacity(){return capacity;}
    private:
        int capacity;
};
#endif

car.hpp

#ifndef CAR_HPP
#define CAR_HPP
#include<iostream>
#include<string>
using namespace std;
class Car{
    public:
        Car(string m,string mo,int y,int od=0):maker(m),model(mo),year(y),odometres(od){}
        void info();
        void update_odometers(int odo);
        
        
    private:
        string maker;
        string model;
        int year;
        int odometres;
        
};

void Car::info(){ 
    cout<<"maker:        "<<maker<<endl;
    cout<<"model:        "<<model<<endl;
    cout<<"year:         "<<year<<endl;
    cout<<"odometres:    "<<odometres<<endl;
}
void Car::update_odometers(int odo){
    if(odo<odometres)
    {
        cout<<"Error updating value\n";
    }
    else
    {
        odometres=odo;
    }
    
}
#endif

electricCar.hpp

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

class ElectricCar:public Car
{
    public:
        ElectricCar(string m,string mo,int y,int b=70):Car(m,mo,y),battery(b){}
        void info();
    private:
        Battery battery;
};
void ElectricCar::info(){
    Car::info();
    cout<<"capacity:     "<<battery.get_capacity()<<"-kWh"<<endl;
} 
#endif

task3.cpp

#include <iostream>
#include "electricCar.hpp"

int main()
{
    using namespace std;

    // test class of Car
    Car oldcar("Hongqi", "h6", 2020);
    cout << "--------oldcar's info--------" << endl;
    oldcar.update_odometers(25009);
    oldcar.info();

    cout << endl;

    // test class of ElectricCar
    ElectricCar newcar("Rongwei", "i5", 2021);
    newcar.update_odometers(1000);
    cout << "\n--------newcar's info--------\n";
    newcar.info();
}

 

实验任务4

 pets.hpp

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

#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);
}