C++primer习题编写Sales_item类

My Code:

//Sales_item.h#include<iostream>#include<string>using namespace std;class Sales_item{public:Sales_item();//构造函数//或者//Sales_item():units_sold("0-201-70535-x"), units_sold(0.0){};~Sales_item();void cin();//输入函数void cout() const;//输出函数Sales_item &sum(const Sales_item &item);//求和操作，定义为const值可以避免复制、改变原来的值double avg_price();//求平均private:string isbn;//国际标准书号unsigned units_sold;//销售的数量double revenue;//收入};

//Sales_item.cpp#include"Sales_item.h"#ifndef SALES_ITEM_H_H#define SALES_ITEM_H_H#include<iostream>#include<string>Sales_item::Sales_item()//构造函数{isbn = "0-201-70353-x";units_sold = 0;revenue = 0.0;}//或者//Sales_item::Sales_item():units_sold("0-201-70535-x"), units_sold(0.0){};Sales_item::~Sales_item(){}void Sales_item::cin(){std::cin >> isbn;std::cin >> units_sold;std::cin >> revenue;}void Sales_item::cout () const{std::cout << isbn << "\t";std::cout << units_sold << "\t";std::cout << revenue << endl;}Sales_item temporary;Sales_item &Sales_item::sum(const Sales_item &item)//定义为const型引用可以避免复制。改变原来的值{if(isbn == item.isbn){temporary.isbn = isbn;temporary.units_sold = units_sold + item.units_sold;temporary.revenue = revenue + item.revenue;return temporary;}std::cout << "Wrong ISBN ???" << endl;return temporary;}double Sales_item::avg_price(){if(units_sold)return revenue/units_sold;elsereturn 0;}#endif

//main.cpp#include<iostream>#include"Sales_item.h"using namespace std;void main(){Sales_item book;cout << "Enter a Sales_item:" << endl;book.cin();book.cout();Sales_item book2;cout << "Enter another Sales_item:" << endl;book2.cin();cout << "The sum of the same book is:\t";book.sum(book2).cout();cout << "The average price of the same book is:\t";cout << book.sum(book2).avg_price();cout << endl;}

Identifying Code:

//Sales_item.h#ifndef SALESITEM_H#define SALESITEM_H#include<iostream>#include<string>class Sales_item{public://Sales_item对象的操作std::istream& input(std::istream& in);std::ostream& output(std::ostream& out) const;double avg_price() const;bool same_isbn(const Sales_item &rhs) const{return isbn == rhs.isbn;}//默认构造函数徐璈初始化内置类型的数据成员Sales_item::Sales_item(): units_sold(0), revenue(0.0) { };private:std::string isbn;unsigned units_sold;double revenue;};#endif

//Sales_item.cpp//自定义的Sales_item类的实现文件（源文件）#include "Sales_item.h"std::istream& Sales_item::input(std::istream& in){double price;in >> isbn >> units_sold >> price;//检验是否读入成功if(in)revenue = units_sold * price;else{//读入失败：将对象复位为默认状态units_sold = 0;revenue = 0.0;}return in;}std::ostream& Sales_item::output(std::ostream& out) const{out << isbn << "\t" << units_sold << "\t" << revenue << "\t" << avg_price();return out;}double Sales_item::avg_price() const{if(units_sold)return revenue/units_sold;elsereturn 0;}

//main.cpp#include "Sales_item.h"#include <iostream>using namespace std;void main(){Sales_item item;//读入并输出一组交易cout << "Enter some transactions(Ctr+Z to end):" << endl;while(item.input(cin)){cout << "The transaction readed is:" << endl;item.output(cout);cout << endl;}}

运行实例：

0-201-78345-x 3 20.000-201-78345-x 2 25.00

终于接触到真正的内容了，开头第一章那个Sales_item.h文件
现在终于开始能够编写了……虽然有点瑕疵，考虑不是很全面，但是终究是开始整体了，加油！！！