c++里的sales_item什么意思?
发布网友
发布时间：2022-04-24 04:32
共3个回答
热心网友
时间：2022-04-20 23:53
sales_item.h是一个需要你自己编写的头文件，其中需要实现某些功能……
热心网友
时间：2022-04-21 01:11
sales_item
看你的链接，是一个类。
也就是商品的类。
如果输入到程序的是
0-201-70353-x 4 24.99
则输出将是
0-201-70353-x 4 99.96 24.99
这里为什么cout<<book
你应该是这里有怀疑吧，为什么可以cout一个对象。
那你就要看看你发的链接下面的代码了，估计你多半是新手看不懂，
或者干脆懒得看吧。
friend std::ostream& operator<<(std::ostream&, const Sales_item&);
注意类中有这样儿一条声明，这句是声明了对象的输出方式和操作符<<的重载。
写就是说，这个对象的cout<<操作跟你平时用的标准库里面的cout<<已经不一样了。
已经被重载成了他自己需要的功能。
目测也就是输出0-201-70353-x 4 99.96 24.99
商品的编号，99.96不知道什么意思，但是应该也是对象的一个属性，然后就是24.99单价。
希望能帮到你，
不明白可以追问，望采纳。追问我看书上说要把sales_item.h源文件复制到工作目录。
这一步是怎么操作？？工作目录是哪里呢？谢谢！
追答所谓的工作目录就是你建立的项目的项目文件夹，
如果你单单复制最后一个文件的话，应该会有问题吧。
前提是这个类的全部定义和初始化等操作都在这个文件中才行。
一般稍微大点儿的都会有一个相应的CPP文件，你可以检查一下有没有这个文件，
如果没有的话，那么直接复制这一个就行。
还有，光复制到工作目录还不够。必须要include到你的项目中才行。
操作就是右击项目，然后添加已有项。选择这个添加就行了。
要在哪个文件中使用这个类就必须引用这个类的头文件。
#include
热心网友
时间：2022-04-21 02:46
源码：
/*
* This file contains code from "C++ Primer, Fifth Edition", by Stanley B.
* Lippman, Josee Lajoie, and Barbara E. Moo, and is covered under the
* copyright and warranty notices given in that book:
*
* "Copyright (c) 2013 by Objectwrite, Inc., Josee Lajoie, and Barbara E. Moo."
*
*
* "The authors and publisher have taken care in the preparation of this book,
* but make no expressed or implied warranty of any kind and assume no
* responsibility for errors or omissions. No liability is assumed for
* incidental or consequential damages in connection with or arising out of the
* use of the information or programs contained herein."
*
* Permission is granted for this code to be used for ecational purposes in
* association with the book, given proper citation if and when posted or
* reproced.Any commercial use of this code requires the explicit written
* permission of the publisher, Addison-Wesley Professional, a division of
* Pearson Ecation, Inc. Send your request for permission, stating clearly
* what code you would like to use, and in what specific way, to the following
* address:
*
* Pearson Ecation, Inc.
* Rights and Permissions Department
* One Lake Street
* Upper Saddle River, NJ 07458
* Fax: (201) 236-3290
*/
/* This file defines the Sales_item class used in chapter 1.
* The code used in this file will be explained in
* Chapter 7 (Classes) and Chapter 14 (Overloaded Operators)
* Readers shouldn't try to understand the code in this file
* until they have read those chapters.
*/
#ifndef SALESITEM_H
// we're here only if SALESITEM_H has not yet been defined
#define SALESITEM_H
// Definition of Sales_item class and related functions goes here
#include <iostream>
#include <string>
class Sales_item {
// these declarations are explained section 7.2.1, p. 270
// and in chapter 14, pages 557, 558, 561
friend std::istream& operator>>(std::istream&, Sales_item&);
friend std::ostream& operator<<(std::ostream&, const Sales_item&);
friend bool operator<(const Sales_item&, const Sales_item&);
friend bool
operator==(const Sales_item&, const Sales_item&);
public:
// constructors are explained in section 7.1.4, pages 262 - 265
// default constructor needed to initialize members of built-in type
Sales_item() = default;
Sales_item(const std::string &book): bookNo(book) { }
Sales_item(std::istream &is) { is >> *this; }
public:
// operations on Sales_item objects
// member binary operator: left-hand operand bound to implicit this pointer
Sales_item& operator+=(const Sales_item&);
// operations on Sales_item objects
std::string isbn() const { return bookNo; }
double avg_price() const;
// private members as before
private:
std::string bookNo; // implicitly initialized to the empty string
unsigned units_sold = 0; // explicitly initialized
double revenue = 0.0;
};
// used in chapter 10
inline
bool compareIsbn(const Sales_item &lhs, const Sales_item &rhs)
{ return lhs.isbn() == rhs.isbn(); }
// nonmember binary operator: must declare a parameter for each operand
Sales_item operator+(const Sales_item&, const Sales_item&);
inline bool
operator==(const Sales_item &lhs, const Sales_item &rhs)
{
// must be made a friend of Sales_item
return lhs.units_sold == rhs.units_sold &&
lhs.revenue == rhs.revenue &&
lhs.isbn() == rhs.isbn();
}
inline bool
operator!=(const Sales_item &lhs, const Sales_item &rhs)
{
return !(lhs == rhs); // != defined in terms of operator==
}
// assumes that both objects refer to the same ISBN
Sales_item& Sales_item::operator+=(const Sales_item& rhs)
{
units_sold += rhs.units_sold;
revenue += rhs.revenue;
return *this;
}
// assumes that both objects refer to the same ISBN
Sales_item
operator+(const Sales_item& lhs, const Sales_item& rhs)
{
Sales_item ret(lhs); // copy (|lhs|) into a local object that we'll return
ret += rhs; // add in the contents of (|rhs|)
return ret; // return (|ret|) by value
}
std::istream&
operator>>(std::istream& in, Sales_item& s)
{
double price;
in >> s.bookNo >> s.units_sold >> price;
// check that the inputs succeeded
if (in)
s.revenue = s.units_sold * price;
else
s = Sales_item(); // input failed: reset object to default state
return in;
}
std::ostream&
operator<<(std::ostream& out, const Sales_item& s)
{
out << s.isbn() << " " << s.units_sold << " "
<< s.revenue << " " << s.avg_price();
return out;
}
double Sales_item::avg_price() const
{
if (units_sold)
return revenue/units_sold;
else
return 0;
}
#endif
