实验4 继承

任务二：

未加virtual

加virtual之后

 同名覆盖原则：基类中的函数和派生类的函数重名时，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：当派生类与基类中有相同成员时，如果要通过派生类对象访问基类中被隐藏的同名成员，可以用基类名和作用域分辨符来限定

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。

派生类的对象可以隐含转换为基类对象

派生类的对象可以初始化基类的引用

派生类的指针可以隐含转换为基类的指针

通过基类对象名、指针只能使用从基类继承的成员。

 

任务三：

battery.hpp

#ifndef _BATTERY_HPP_
#define _BATTERY_HPP_
#include<iostream>
class Battery {
private:
    int capacity;
public:
    Battery(int c = 70): capacity(c){}
    int get_capacity() const {
        return capacity;
    }
};

#endif

car.hpp

#ifndef _CAR_HPP_
#define _CAR_HPP_
#include<iostream>
#include<string>

using namespace std;

class Car {
private:
    string maker, model;
    int year, odometers;
public:
    Car(string maker1, string model1, int year1);
    void info();
    void update_odometers(int m);
};

Car::Car(string maker1, string model1, int year1) :
    maker(maker1), model(model1), year(year1) {
    odometers = 0;
}

void Car::info() { 
    cout << "maker:       " << maker << endl;
    cout << "model:       " << model << endl;
    cout << "year;        " << year << endl;
    cout << "odometers:   " << odometers << endl;
}
void Car::update_odometers(int m) {
    if (m < odometers)
        cout << "里程数更新失败！" << endl;
    else
        odometers = m;
    return;
}

#endif

electricCar.hpp

#ifndef _ELECTRICCAR_HPP_
#define _ELECTRICCAR_HPP_
#include<iostream>
#include"battery.hpp"
#include"car.hpp"
#include<string>

class ElectricCar : public Car, public Battery {
private:
    Battery battery;
public:
    ElectricCar(string maker1, string model1, int year1, int c = 70);
    void info();
};

ElectricCar::ElectricCar(string maker1, string model1, int year1, int c) :
    Car(maker1, model1, year1), Battery(c) {}

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;

    Car oldcar("Audi", "a4", 2016);
    cout << "---------oldcar's info---------" << endl;
    oldcar.update_odometers(25000);
    oldcar.info();

    cout << endl;

    ElectricCar newcar("Tesla", "model s", 2016);
    newcar.update_odometers(2500);
    cout << "\n--------newcar's info---------\n";
    newcar.info();

}

实验结果截图：

任务四：

pets.hpp

#ifndef _PETS_HPP_
#define _PETS_HPP_
#include<iostream>
#include<cstring>
using namespace std;

class MachinePets {
private:
    string nickname;
public:
    MachinePets(const string s):nickname(s){}
    virtual string talk() {
        return "la la la";
    }
    string get_nickname() const {return 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);
}

实验结果截图：