实验四 继承

任务2 源代码

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);
    fun(&r1);
    fun(&c1);
}

 

 

 归纳总结

①同名覆盖原则：当派生类和基类中有相同成员时，若未强行指明，则通过派生类对象使用的是派生类的中的同名成员

②二元作用域分辨符：若果要通过派生类对象访问基类中被覆盖的同名成员，应使用基类名加二元作用域分辨符来限定

③类型兼容原则：基类对像可以使用公有派生类的对象来替代

任务3 源代码

battery.hpp

#pragma once
#include "electricCar.hpp"
using namespace std;

class Battery
{
public:
    Battery(int capacity0 = 70);
    ~Battery() = default;
    int get_capacity() const;
private:
    int capacity;
};
Battery::Battery(int capacity0) :capacity{ capacity0 }
{
    ;
}
int Battery::get_capacity() const
{
    return this->capacity;
}

car.hpp

#pragma once
#include <iostream>
#include <iomanip>
using namespace std;

class Car
{
public:
    Car(string maker0, string model0, int year0, int odometers0 = 0);
    ~Car() = default;
    void info() const;
    void update_odometers(int new_odometers);
private:
    string maker;
    string model;
    int year;
    int odometers;
};

Car::Car(string maker0, string model0, int year0, int odometers0) :maker{ maker0 }, model{ model0 }, year{ year0 }, odometers{ odometers0 }
{
    ;
}
void Car::info() const
{
    cout << setw(20) << setiosflags(ios::left) << "maker:";
    cout << this->maker << endl;
    cout << setw(20) << setiosflags(ios::left) << "model:";
    cout << this->model << endl;
    cout << setw(20) << setiosflags(ios::left) << "year:";
    cout << this->year << endl;
    cout << setw(20) << setiosflags(ios::left) << "odometers:";
    cout << this->odometers << endl;
}
void Car::update_odometers(int new_odometers)
{
    if (this->odometers >= new_odometers)
    {
        cout << "Error updating value";
        return;
    }
    this->odometers = new_odometers;
}

electricCar.hpp

#pragma once
#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);
    ~ElectricCar() = default;
    void info() const;
private:
    Battery battery;
};
ElectricCar::ElectricCar(string maker0, string model0, int year0, int odometers0, int capacity0) :Car(maker0, model0, year0, odometers0), battery(capacity0)
{
    ;
}
void ElectricCar::info() const
{
    Car::info();
    cout << setw(20) << setiosflags(ios::left) << "capacity:";
    cout << battery.get_capacity() << "-kwh" << endl;
}

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();

    cout << endl;

    ElectricCar newnewcar("Mercedes-Benz", "SLS", 2020, 3000, 100);
    cout << "\n--------new newcar's info--------\n";
    newnewcar.info();
}

 

 

 任务4 源代码

pets.hpp

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

class MachinePets
{
public:
    MachinePets(const string s) : nickname{s} { ; }
    ~MachinePets() = default;
    string get_nickname() const { return this->nickname; }
    virtual string talk() = 0;

private:
    string nickname;
};

class PetCats : public MachinePets
{
public:
    PetCats(const string s) : MachinePets(s) { ; }
    ~PetCats() = default;
    virtual string talk() 
    { 
        string s = "miao wu~";
        return s;
    }
};

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

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);
}