重载运算符 <<

#pragma once#ifndef BATTERY_H#define BATTERY_Hclass battery{public:    battery(int batterySize1 = 70);    int getbattery()const;private:    int batterySize;};#endif

battery.h

#pragma once#ifndef CAR_H#define CAR_H#include
     
      #include
      
       using std::string;using std::ostream;class car{    public        :            car(string maker1, string model1, int year1, int odometer1 = 0);            void updateOdometer(int a);            friend  ostream &operator<<(ostream &out, const car &c2);private:    string maker;    string model;    int year;    int odometer;};#endif

car.h

#pragma once#ifndef ELECTRICCAR_H#define ELECTRICCAR_H#include
     
      #include"car.h"#include"battery.h"using std::string;class ElectricCar :public car,public battery{public:    ElectricCar(string maker2, string model2, int year2, int odometer2 = 0, int battery1 = 70);    friend ostream &operator<<(ostream &out,const ElectricCar &c1);    private:    battery batterySize;};#endif

electricCar.h

#include"battery.h"battery::battery(int batterySize1) :batterySize(batterySize1){}int battery::getbattery()const{    return batterySize;}

battery.cpp

#include"car.h"#include
     
      #include
      
       using namespace std;using std::endl;using std::cout;car::car(string maker1, string model1, int year1, int odometer1) :maker(maker1), model(model1), year(year1), odometer(odometer1){}void car::updateOdometer(int a){    if (a < odometer)    {        cout << "wrong odometer" << endl;        exit(0);    }    odometer = a;}ostream &operator<<(ostream &out, const car &c2){    out << "maker:" << c2.maker << endl        << "model:" << c2.model << endl        << "year:" << c2.year << endl        << "odometer:" << c2.odometer << endl;    return out;}

car.cpp

#include"electricCar.h"using namespace std;ElectricCar::ElectricCar(string maker2, string model2, int year2, int odometer2, int battery1) :car(maker2, model2, year2, odometer2), batterySize(battery1) {}ostream &operator<<(ostream &out, const ElectricCar &c1){        car c2 = c1;    battery a = c1.batterySize;    out << c2         << "batterySize:" << a.getbattery() << "-kWh" << endl;    return out;}

electricCar.cpp

#include 
     
      #include
      
       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;}

main.cpp

#ifndef ARRAY_INT_H#define ARRAY_INT_Hclass 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

arrayint.h

#include "arrayInt.h"#include 
     
      #include 
      
       using std::cout;using std::endl;ArrayInt::ArrayInt(int n, int value): size(n) {    p = new int[size];        if (p == nullptr) {        cout << "fail to mallocate memory" << endl;        exit(0);     }         for(int i=0; i

arrayint.cpp

因为main没有添加改动，就不添加了。

实验总结：

1、一开始在electricCar重载 << 的时候，参考了书上的做法，用了很多get去获取数据，但在最后出现了错误（errorLNK2019：无法解析的外部符号)，然后强制把eleccar转成了car，但不用eleccar继承battery，仍会出现上述错误，公有继承后，错误消除。

2、在array的实验里，重载的时候忘记加&符号，导致main.cpp中，b[0]变成了无法更改的左值。

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