task2源代码virtual

#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);
}

运行截图

 

 task2 

#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);
}

 

 

1.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；

2.二元作用域分辨符：

当派生类新增成员隐藏了基类的同名成员，这时使用”对象名.成员名“的访问方式只能访问到派生类新增的成员。对基类同名成员的访问，只能通过基类名和作用域分辨符来实现。

electricCar.hpp

#include <iostream>
#include <string>
using namespace std;
class Car{
    private:
        string maker;
        string model;
        int year;
        int odometers;
    public:
        Car(string maker0,string model0,int year0,int odometers0=0):maker(maker0),model(model0),year(year0),odometers(odometers0){}
        void info()const{
            cout<<"maker:\t\t"<<maker<<endl;
            cout<<"model:\t\t"<<model<<endl;
            cout<<"year:\t\t"<<year<<endl;
            cout<<"odometers:\t"<<odometers<<endl;
        }
        int update_odometers(const int &obj){
            if(obj<odometers){
                cout<<"警告！更新数值有误。"<<endl;
            }
            else
            odometers=obj;
        }
};
class Battery{
    private:
        int capacity;
    public:
        Battery(int capacity0=70):capacity(capacity0){}
        int get_capacity(){return capacity;}
};
class ElectricCar:public Car{
    private:
        Battery battery;
    public:
        ElectricCar(string maker0,string model0,int year0,int battery0=70,int odometers0=0):Car(maker0,model0,year0,odometers0),battery(battery0){}
        void info(){
            Car::info();
            cout<<"capacity:\t"<<battery.get_capacity()<<"-kwh"<<endl;
        }
};

task3

#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();
}

运行截图

 

pets.hpp

#include <iostream>
#include <string>
using namespace std;
class MachinePets{
    private:
        string nickname;
    public:
        MachinePets(const string s):nickname(s){}
        string get_nickname()const{
            return nickname;
        }
        virtual string talk()
        {
            return "";
        }
}; 
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~";
    }
};

task4

#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);
}

运行截图