实验四

task2.cpp

#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); std::cout << "\n";
    fun(&r1); std::cout << "\n";
    fun(&c1);
}

 

 

 同名覆盖原则：如果派生类声明了一个与基类成员函数同名的函数成员，那么直接使用成员名只能访问派生类的对应成员。

二元作用域分辨符：使用作用域分辨符和基类名来访问被隐藏的基类成员函数。

类型兼容原则：派生类对象可以作为基类对象使用，但是只能使用从基类继承的成员。

 

调整后：

#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); std::cout << "\n";
    fun(&r1); std::cout << "\n";
    fun(&c1);
}

运行截图：

 使用虚函数之前，调用的是基类函数成员；定义虚函数后，调用的是派生类函数成员。

 

task3.hpp

#ifndef ELECTRICCAR_H
#define ELECTRICCAR_H
#include<iostream>
#include<string>
#include<iomanip>
using namespace std;
class Car
{
public:
    Car(string s1, string s2, int a);
    void info();
    void update_odometers(int d);
private:
    string maker, model;
    int year, odometers;
};
Car::Car(string s1, string s2, int a)
{
    maker = s1;
    model = s2;
    year = a;
    odometers = 49999;
}
void Car::info()
{
    cout << left << setw(15) << setfill(' ') << "maker:" << maker << endl;
    cout << left << setw(15) << setfill(' ') << "model:" << model << endl;
    cout << left << setw(15) << setfill(' ') << "year:" << year << endl;
    cout << left << setw(15) << setfill(' ') << "odometers:" << odometers << endl;
}
void Car::update_odometers(int d)
{
    if (d < odometers)
        cout << "error"<<endl;
    else
        odometers = d;
}

class Battery
{
public:
    Battery(int n = 70);
    int get_capacity();
private:
    int capacity;
};
Battery::Battery(int n)
{
    capacity = n;
}
int Battery::get_capacity()
{
    return capacity;
}

class ElectricCar :public Car
{
public:
    ElectricCar(string s1, string s2, int b, int c=70) :Car(s1, s2, b), battery(c) {}
    void info();
private:
    Battery battery;
};
void ElectricCar::info()
{
    Car::info();
    cout << left << setw(15) << setfill(' ') << "capacity:" << battery.get_capacity()<<"-kwh"<< endl;
}
#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();
}

运行截图：

 

task4.hpp

#ifndef PETS_H
#define PETS_H
#include<iostream>
#include<string>
using namespace std;

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

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

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

task4.cpp

#include<iostream>
#include<string>
#include"pets.hpp"
void play(MachinePets* ptr)
{
    std::cout << ptr->get_nickname() << " says " << ptr->talk() << std::endl;
}
int main()
{
    PetsCats cat("miku");
    PetDogs dog("da huang");
    play(&cat);
    play(&dog);
}

运行截图：