实验四 继承

2.实验任务2

#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);
}

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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。

二元作用域分辨符

　　用法为类名::成员，用来访问基类中的同名成员。

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。通过公有继承，派生类得到了基类中除构造函数、析构函数之外的所有成员。

 

3.实验任务3

Battery.hpp

class Battery
{
public:
    Battery(int capa = 70) :capacity{ capa } {}
    int get_capacity()
    {
        return capacity;
    }
private:
    int  capacity;
};

Car.hpp

#include<iostream>
#include<string>
#include<iomanip>

class Car
{

public:
    Car(string Maker, string Model, int Year, int Odometers = 0) :
        maker{ Maker }, model{ Model }, year{ Year },odometers{Odometers}{}

    void info()
    {
        const int N = 18;
        cout << setw(N) <<left<< "maker:" << maker << endl
            << setw(N) << left << "model:" << model << endl
            << setw(N) << left << "year:" << year << endl
            << setw(N) << left << "odometers:" << odometers << endl;
    }
    void update_odometers(int odom)
    {
        if (odom < odometers)
        {
            cout << "wrong info" << endl;
            return;
        }
        odometers = odom;
    }
private:
    string maker;
    string model;
    int year;
    int odometers;
};

ElectricCar.hpp

#ifndef ELECTRICCAR_H
#define ELECTRICCAR_H

#include<iostream>
#include<string>
#include<iomanip>

using namespace std;

class ElectricCar :public Car
{
public:
    ElectricCar(string Maker,string Model,int Year,int Capacity=70):Car(Maker,Model,Year),battery{Capacity}{}
    void info()
    {
        Car::info();
        cout << setw(18) << "capacity:" << battery.get_capacity()<<"-kWh"<< endl;
    }
private:
    Battery battery;
};


#endif

task3.cpp

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

int main()
{
    using namespace std;

    // test class of Car
    Car oldcar("Audi", "a4", 2018);
    cout << "--------oldcar's info--------" << endl;
    oldcar.update_odometers(11451);
    oldcar.info();

    cout << endl;

    // test class of ElectricCar
    ElectricCar newcar("Tesla", "model s", 2016);
    newcar.update_odometers(1145);
    cout << "\n--------newcar's info--------\n";
    newcar.info();
}

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 4.实验任务4

pets.hpp

#ifndef PETS_H
#define PETS_H

#include<iostream>
#include<string>
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 "mao 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);
}

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