#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);
}

測試結果：

歸納總結,

同名覆蓋原則：派生類與基類有相同成員時，若未強行指名，則通過派生類物件使用的是派生類的同名成員；

二元作用域分辨域,

::二元作用域分辨符：類名::成員

型別相容原則,

派生類的物件可以隱含轉換為基類的物件
派生類的物件可以初始化基類的引用

修改後:

#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);
}

task3

task.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();
}

car.hpp

#ifndef Car_hpp
#define Car_hpp

#include<iostream>
#include<string>

using namespace std;

class Car
{
    public:
        Car(string maker1, string model1, int year1, int odometers1=0): maker(maker1), model(model1), year(year1), odometers(odometers1) { };
        ~Car(){}
        virtual void info();
        void update_odometers(int new_odometers);
    private:
        string maker;
        string model;
        int year;
        int odometers;
};

void Car::info(){
    cout<<"maker:\t\t"<<maker<<endl;
    cout<<"model:\t\t"<<model<<endl;
    cout<<"year:\t\t"<<year<<endl;
    cout<<"odometers:\t"<<odometers<<endl;
}

void Car::update_odometers(int new_odometers){
    if(new_odometers<odometers)
    cout<<"更新數值有誤"<<endl;
    else
    odometers=new_odometers;
}

#endif

electriccar.hpp

#ifndef ElectricCar_hpp
#define ElectricCar_hpp

#include<iostream>
#include<string>
#include"Car.hpp"
#include"Battery.hpp"

using namespace std;

class ElectricCar: public Car{
    public:
     ElectricCar(string a, string o, int y, int c=60): Car(a, o, y), battery(c) {
     };
     void info();
    private:
        Battery battery;
};

void ElectricCar::info(){
    Car::info();
    cout<<"capacity:    "<<battery.get_capacity()<<"-kwh"<<endl;
}

#endif

battery.hpp

#ifndef Battery_hpp
#define Battery_hpp

using namespace std;

class Battery{
    public:
        Battery(int c=60): capacity(c){
        };
        int get_capacity(){
            return capacity;
        }
    private:
        int capacity;
};

#endif

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);
}

pets.hpp

#ifndef PETS_HPP
#define PETS_HPP
#include<string>
using namespace std;

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

string MachinePets::get_nickname() const{
       return nickname;
}

string MachinePets::talk(){
    return "hahahha";
}

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

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

#endif