实验四：类的继承派生和多态

【实验结论】

#1.车辆基本信息管理

#include <iostream>
using namespace std;
#include "Car.h"
#include "electricCar.h" 

int main() {
    // 测试Car类 
    Car oldcar("Audi","a4",2016);
    cout << "--------oldcar's info--------" << endl;
    oldcar.updateOdometer(25000);
    cout << oldcar << endl;

    // 测试ElectricCar类 
    ElectricCar newcar("Tesla","model s",2016);
    newcar.updateOdometer(2500);
    cout << "\n--------newcar's info--------\n"; 
    cout << newcar << endl;

    system("pause");
    
    return 0;
}

#ifndef BATTERY_H
#define BATTERY_H
#include<iostream>
using namespace std;
class Battery{
public:
    Battery(int batterySize0=70);
    int x();

private:
    int batterySize;

};

#endif

#include"Battery.h"
#include<iostream>
using namespace std;
Battery::Battery(int batterySize0):batterySize(batterySize0){

}
int Battery::x(){
    return batterySize;
}

#ifndef CAR_H
#define CAR_H
#include<iostream>
using namespace std;
class Car{
public:
    Car(string maker0="",string model0="",int year0=2000,int odometer0=0);
    friend ostream &operator<<(ostream& out,const Car &c);
    int updateOdometer(int newdodmeter);

private:
    string maker;
    string model;
    int year;
    int odometer;

};
#endif

#include"Car.h"
#include"Battery.h"
#include"ElectricCar.h"
#include<iostream>
using namespace std;
Car::Car(string maker0,string model0,int year0,int odometer0):maker(maker0),model(model0),year(year0),odometer(odometer0){
}

ostream &operator<<(ostream& out,const Car &c){
    out<<"maker"<<":"<<c.maker<<endl
        <<"model"<<":"<<c.model<<endl
        <<"year"<<":"<<c.year<<endl
        <<"odometer"<<":"<<c.odometer<<endl;
    return out;
}

int Car::updateOdometer(int newodometer){
    if(newodometer>odometer){
        odometer=newodometer;
        return odometer;
    }
    else
        cout<<"newodometer is error"<<endl;

}

#ifndef ELECTRICCAR_H
#define ELECTRICCAR_H
#include<iostream>
#include"Car.h"
#include"Battery.h"
using namespace std;
class ElectricCar:public Car{
public:
    ElectricCar(string maker0="",string model0="",int year0=2000,int odometer0=0);


    friend ostream &operator<<(ostream &out,const ElectricCar &m);

private:
    Battery battery;
    int batterySize;
};
#endif

include"Car.h"
#include"Battery.h"
#include"ElectricCar.h"
#include<iostream>
using namespace std;
ElectricCar::ElectricCar(string maker0,string model0,int year0,int odometer0):Car(maker0,model0,year0,odometer0){
    batterySize=battery.x();
}
ostream &operator<<(ostream &out,const ElectricCar &m){
    out<<Car(m)
        <<"batterySize"<<":"<<m.batterySize<<"-kWh"<<endl;
    return out;
}

#2.重载运算符[ ]

#include<iostream>
#include "arrayInt.h"
using namespace std;
int main() {
    // 定义动态整型数组对象a，包含2个元素，初始值为0
    ArrayInt a(2);
    a.print();
    
    // 定义动态整型数组对象b，包含3个元素，初始值为6
    ArrayInt b(3, 6);
    b.print();

    // 通过对象名和下标方式访问并修改对象元素
    b[0] = 2;
    cout << b[0] << endl;
    b.print();

    system("pause");

    return 0;
}

#ifndef ARRAY_INT_H
#define ARRAY_INT_H

class ArrayInt{
    public:
        ArrayInt(int n, int value=0);
        ~ArrayInt();
        int& operator[](int n);// 补足:将运算符[]重载为成员函数的声明
       
        void print(); 
    private:
        int *p;
        int size;
};

#endif

#include "arrayInt.h"
#include <iostream>
#include <cstdlib>
using std::cout;
using std::endl;

ArrayInt::ArrayInt(int n, int value): size(n) {
    p = new int[size];
    
    if (p == 0) {
        cout << "fail to mallocate memory" << endl;
        exit(0); 
    } 
    
    for(int i=0; i<size; i++)
        p[i] = value;
}

ArrayInt::~ArrayInt() {
    delete[] p;
}

void ArrayInt::print() {
    for(int i=0; i<size; i++)
        cout << p[i] << " ";
    cout << endl;
}

int &ArrayInt::operator[](int n){
    return p[n];
    
}// 补足:将运算符[]重载为成员函数的实现

 

实验总结：

1.第二个程序很简单，基本上完全可以参照书上的自增自减，结合一下老师上课讲的加减，甚至比这些都简单。运算符重载为成员函数一般语法形式为：返回值类型 operator 运算符（形参表）{函数体}。运算符重载为非成员函数一般语法形式为：返回值类型 operator 运算符（形参表）{函数体}。有些加减运算要根据程序具体要求进行改进，而不是直接拿来使用，例如时钟这类程序，时分秒皆有其变化的范围。

2.第一个程序综合了很多知识点，类似于继承派生，以及运算符重载，此程序中运算符重载运用了友元函数来实现，友元函数属于非成员函数，一般用友元函数输出较为特别，使用“out”，并且返回值为“out"。当一个函数继承另一个函数时，也可以继承其友元函数的运行过程，并且只继承其public。此程序中的electriccar与battery是组合关系，electriccar中的battery即来自battery类。

评论地址：

https://www.cnblogs.com/yidaoyigexiaopenyou/p/10902587.html

https://www.cnblogs.com/lyc1103/p/10890495.html

https://www.cnblogs.com/charlotte00/p/10889286.html