实验四 继承

task2.cpp 改动后代码

#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);
}

改动前运行结果

 

改动后运行结果截图

 

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；

                        如果要通过派生类的对象访问基类被覆盖的同名成员，需要加对象名.基类名::同名成员来限定

二元作用域分辨符：用法：类名::成员

                               在多重继承的情况下，如果两个基类中存在相同的变量名，可以使用作用域运算符来进行区分

类型兼容原则：类型兼容规则是指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。

类型兼容原则中在替代之后，派生类对象就可以作为基类的对象使用，但是只能使用从基类继承的成员。

 

task3

battery.hpp

#include<iostream>
using namespace std;
class Battery{
    public:
        int capacity;
        Battery(int capacity0=70):capacity(capacity0){
        }
        int get_capacity();
        
};
int Battery::get_capacity()
{
    return capacity;
}

car.hpp

#include<iostream>
#include<string>
#include<iomanip>
using namespace std;
class Car{
    public:
        string maker,model;
        int year,odometers;
        
        Car(string maker0,string model0,int year0,int odometers0=0):maker(maker0),model(model0),year(year0),odometers(odometers0){
        }
        void info();
        void update_odometers(int odometers);
};
void Car::info()
{
    cout<<std::left<<setw(12)<<"maker:"<<maker<<endl;
    cout<<std::left<<setw(12)<<"model:"<<model<<endl;
    cout<<std::left<<setw(12)<<"year:"<<year<<endl;
    cout<<std::left<<setw(12)<<"odometers:"<<odometers<<endl;
}
void Car::update_odometers(int odometers1)
{
    if(odometers1<odometers)
    {
        cout<<"更新数值有误"<<endl; 
    }
    else odometers=odometers1;
}

electricCar.hpp

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

class ElectricCar:public Car{
    public:
        ElectricCar(string maker0,string model0,int year0,int odometers0=0,int capacity0=70):Car(maker0,model0,year0,odometers0),battery(capacity0){
    };
        void info();
        
    private:
        Battery battery;
};
void ElectricCar::info()
{
    Car::info();
    cout<<std::left<<setw(12)<<"capacity:"<<battery.capacity<<"-kWh"<<endl;
}

task3.cpp

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

int main()
{
    using namespace std;

    // test class of Car
    Car oldcar("aaa", "a11",9999);
    cout << "--------oldcar's info--------" << endl;
    oldcar.update_odometers(100000);
    oldcar.info();

    cout << endl;

    // test class of ElectricCar
    ElectricCar newcar("zzz", "z9", 1217);
    newcar.update_odometers(5200);
    cout << "\n--------newcar's info--------\n";
    newcar.info();
}

 

运行结果如下

 

task4

pets.hpp

#include<iostream>
#include<string>
using namespace std;

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

class PetCats:public MachinePets
{
    public:
        PetCats(const string s):MachinePets(s){
    }
        string talk();
};
string PetCats::talk()
{
    return "mao wu~";
}

class PetDogs:public MachinePets
{
    public:
        PetDogs(const string s):MachinePets(s){
        }
        string talk(); 
};
string PetDogs::talk()
{
    return "wang wang~";
}

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);
}

 

运行结果如下