实验四 类的继承派生和多态
Posted zuiyankh
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一、实验内容
1、车辆基本信息管理
基于Car类派生出ElectricCar类、派生类ElectricCar中新增数据成员Battery类对象。
#ifndef BATTERY_H #define BATTERY_H class Battery { public: Battery(int batterySize0=70); int getSize(); private: int batterySize; }; #endif
#ifndef CAR_H #define CAR_H #include<string> #include<iostream> using std::string; using std::ostream; class Car { public: Car(string maker0, string model0, int year0, int odometer0=0); void updateOdometer(int odometerN); friend ostream & operator<<(ostream &out, const Car &c); private: string maker; string model; int year; int odometer; }; #endif
#ifndef ELECTRIC_H #define ELECTRIC_H #include"battery.h" #include"car.h" class ElectricCar:virtual public Car{ public: ElectricCar(string maker0,string model0,int year0,int odometer0=0); friend ostream & operator<<(ostream &out, const ElectricCar &c); private: Battery battery; }; #endif
#include"battery.h" #include<iostream> using std::cout; using std::endl; Battery::Battery(int batterySize0 ):batterySize(batterySize0) { } int Battery::getSize(){ return batterySize; }
#include"car.h" #include<iostream> using std::cout; using std::endl; Car::Car(string maker0, string model0, int year0, int odometer0 ) :maker(maker0), model(model0), year(year0), odometer(odometer0) { } void Car::updateOdometer(int odometerN) { if (odometerN < odometer) { cout << "WRONG DATA!"; exit(0); } else odometer = odometerN; } ostream & operator<<(ostream &out, const Car &c) { cout << "maker:" << c.maker << endl; cout << "model:" << c.model << endl; cout << "year:" << c.year << endl; cout << "odometer:" << c.odometer << endl; return out; }
#include"electriccar.h" #include<iostream> using std::cout; using std::endl; ElectricCar::ElectricCar(string maker0, string model0, int year0, int odometer0 ):Car(maker0,model0,year0,odometer0) { } ostream & operator<<(ostream &out, const ElectricCar &c) { Car a(c); cout<<a<<endl; Battery m=c.battery; cout << "batterySize:" <<m.getSize()<<"-kWh"<< endl; return out; }
#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; }
效果如下:
2、补足程序
重载运算符[]为一维动态整形数组类ArrayInt的成员函数,使得通过动态整形数组对象名和下标可以 访问对象中具体元素。
#ifndef ARRAY_INT_H #define ARRAY_INT_H class ArrayInt{ public: ArrayInt(int n, int value=0); ~ArrayInt(); // 补足:将运算符[]重载为成员函数的声明 // ××× int& operator[](int i); 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 == nullptr) { 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; } // 补足:将运算符[]重载为成员函数的实现 // ××× int & ArrayInt::operator[](int i){ return p[i]; }
#include <iostream> using namespace std; #include "arrayInt.h" 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; }
效果如下:
二、实验小结
虽然测试出结果,有几点还是不太懂:
- electriccar.cpp中,Car a(c); 我将ElectricCar类c赋值给Car类a,这是反复试探的结果,虽然意外成功,还是不太理解;
- 什么时候用&也不是很清楚。不对了,就加上&试试,偶尔可以猜对,却不是理解后的结果。
希望大佬不吝赐教,万分感激。
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