实验四 继承

任务二：

#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);
}

 改动后：

 同名覆盖原则：派生类对象调用派生类和基类均有的函数时，派生类的会覆盖掉基类的

 二元作用域分辨符：限定作用的类

 类型兼容原则：派生类类型对象可以作为基类对象使用，但调用函数仅会调用基类的函数

 不同：改动后运行时调用对象类型类的函数

 

任务三：

//battery.hpp
#ifndef BATTER_HPP
#define BATTER_HPP
#include<iostream>
#include<string>
class Battery
{
public:
    Battery(int c = 70) :capacity(c) {};
    int get_capacity() { return capacity; };
protected:
    int capacity;
};
#endif

//car.hpp
#ifndef CAR_HPP
#define CAR_HPP
#include<iostream>
#include<string>
#include<iomanip>
class Car
{
public:
    Car(std::string Maker, std::string Model, int Year, int Odometers = 0)
        :maker(Maker), model(Model), year(Year), odometers(Odometers) {};
    void info();
    int update_odometers(int update);
private:
    std::string maker, model;
    int year, odometers;
};
void Car::info()
{
    using namespace std;
    cout<<left<<setw(12)<< "maker:" << maker << endl
        <<setw(12) << "model:" << model << endl
        <<setw(12) << "year:" << year << endl
        <<setw(12) << "odometers:" << odometers << endl;

};
int Car::update_odometers(int update)
{

    if (odometers + update >= odometers)
    {
        odometers += update;
        return odometers;
    }
    else
        std::cout << "更新数值有误" << std::endl;

}
#endif

//electricCar.hpp
#ifndef ELECTRICAR_HPP
#define ELECTRICAR_HPP
#include"battery.hpp"
#include"car.hpp"
#include<iostream>
#include<string>

class ElectricCar :public Car
{
public:
    ElectricCar(std::string Maker, std::string Model, int Year, Battery batter=70, int Odometers = 0)
        :Car(Maker, Model, Year, Odometers), battery(batter){};
    void info();
private:
    Battery battery;
};
void ElectricCar::info()
{
    Car::info();
    std::cout << std::setw(12) <<"capacity:"<< battery.get_capacity() << "-kWh";
}
#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();
}

 

 任务四：

//pets.hpp
#ifndef PETS_HPP
#define PETS_HPP
#include<iostream>
#include<string>
using std::string;
class MachinePets
{
public:
    MachinePets(const string s) :nickname(s) {};
    virtual string talk() { return ""; };
    string get_nickname() { return nickname; }
private:
    string nickname;
};
class PetCats :public MachinePets
{
public:
    PetCats(const string s) :MachinePets(s) {};
    string talk() { return "miao 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);
}