实验四 继承

目录

• 实验四 继承
  • 实验任务二
    • task2.cpp
    • 运行结果
    • 总结
  • 实验任务三
    • Battery.hpp
    • Car.cpp
    • ElectricCar.hpp
    • task3.cpp
    • 运行结果
  • 实验任务四
    • pets.hpp
    • task.cpp
    • 运行结果

实验四 继承

实验任务二

task2.cpp

#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);
}

运行结果

总结

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

实验任务三

Battery.hpp

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

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

Car.cpp

#include <iostream>
#include <string>
#include <iomanip>
using namespace std;
class Car {
public:
    Car() = default;
    Car(string _maker, string _model, int _year, int _odo = 0)
        :maker(_maker), model(_model), year(_year), odometers(_odo){}
    void info()
    {
        cout.setf(ios::left);
        cout << setw(15) << "maker:" << maker << endl;
        cout << setw(15) << "model:" << model << endl;
        cout << setw(15) << "year:" << year << endl;
        cout << setw(15) << "odometers:" << odometers << endl;
    }
    void update_odometers(int _meters)
    {
        if ( _meters < odometers ) {
            cout << "Incorrect Value!!!" << endl;
            return;
        }
        else {
            odometers = _meters;
        }
    }
private:
    string maker;
    string model;
    int year;
    int odometers;
};

ElectricCar.hpp

#include "battery.hpp"
#include "car.hpp"
#include <iostream>

using namespace std;

class ElectricCar :public Car {
public:
    ElectricCar(string _maker, string _model, int _year, int _odo = 0, Battery _bat = Battery())
        :Car(_maker, _model, _year, _odo),battery(_bat){}
    void info()
    {
        Car::info();
        cout << setw(15) << "capacity:" << battery.get_capacity()
            << "-kWh" << endl;
    }
private:
    Battery battery;
};

task3.cpp

#include <iostream>
#include "electricCar.hpp"
int main()
{
    using namespace std;
    // test class of Car
    Car oldcar("PPTTYY", "b1", 2021);
    cout << "--------oldcar's info--------" << endl;
    oldcar.update_odometers(2288);
    oldcar.info();
    cout << endl;
    // test class of ElectricCar
    ElectricCar newcar("slkadj", "ksjdl", 1234);
    newcar.update_odometers(423749);
    cout << "\n--------newcar's info--------\n";
    newcar.info();
}

运行结果

实验任务四

pets.hpp

#include <iostream>
#include <string>

using namespace std;

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

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~";
    }
};

task.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