[英]reading data from a text file into a C++ struct
This is a program which is supposed to read an inventory of books from a text file (each line of the text file contains a different field, in the correct order, for each book). 这是一个应该从文本文件中读取书籍清单的程序(文本文件的每一行都以正确的顺序为每本书包含一个不同的字段)。 For some reason the routine continues indefinitely. 由于某种原因,例程将无限期地继续。 The "eof" error trapping seems to not catch the end of file. “ eof”错误陷阱似乎无法捕获文件末尾。 Can anybody give me an idea what is wrong? 谁能告诉我什么地方出了问题? Please remember I am a true newbie in the c++ world, but not a newbie to programming. 请记住,我是c ++领域的真正新手,但不是编程的新手。
First, the structure definition for Book 一,Book的结构定义
// structure definition
struct Book
{ string isbn;
string title;
string author;
string publisher;
int quantity;
float price; };
I have included the proper header files. 我已经包含了正确的头文件。 Below is the routine that seems to not be working. 以下是似乎无效的例程。 I put in some cout << "made it to line 1" endl; 我放了一些提示<<“到达第1行” endl; code to see the progress of the routine, and it simply repeats fetching data from the text file. 代码以查看例程的进度,并且只需重复从文本文件中获取数据即可。 The text file has just 6 books in it, so it should end reading through the text file rather quickly. 文本文件中只有6本书,因此应该很快结束文本文件的阅读。
Thank you, kindly, for any assistance! 谢谢您的协助!
void readInventory(string fileName, vector<Book>& inventory)
{
ifstream instream;
// tries to open the file
instream.open(fileName);
// checkes if the file is open
if (instream)
{
// string line;
// reads through the file line by line
while (!instream.eof())
{
Book newBook;
// read book from text file
instream >> newBook.isbn;
instream >> newBook.title;
instream >> newBook.author;
instream >> newBook.publisher;
instream >> newBook.quantity;
instream >> newBook.price;
// add this book to inventory
inventory.push_back(newBook);
}
instream.close();
showMessage(to_string(inventory.size()) + " books were successfully added to inventory");
}
// if failed to open the file
else
showMessage("Cannot open the file. Make sure the file name is correct");
}
You can write program like this . 您可以编写这样的程序。
#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <cmath>
#include <set>
#include <queue>
#include <fstream>
#include <sstream>
using namespace std;
// structure definition
struct Book
{ string isbn;
string title;
string author;
string publisher;
int quantity;
float price;
};
void fillBook(const std::string& line,Book& book)
{
std::stringstream is(line);
std::string tempStr;
short cnt = 0;
while(std::getline(is, tempStr, ' '))
{
if(cnt ==0)
book.isbn =tempStr;
else if(cnt ==1)
book.title = tempStr;
else if(cnt ==2)
book.author = tempStr;
else if(cnt ==3)
book.publisher= tempStr;
else if(cnt ==4)
book.quantity = atoi(tempStr.c_str());
else if(cnt == 5)
book.price = atof(tempStr.c_str());
++cnt;
}
}
void readInventory(string fileName, vector<Book>& inventory)
{
ifstream instream;
// tries to open the file
instream.open(fileName);
// checkes if the file is open
if (instream)
{
// string line;
// reads through the file line by line
std::string line;
while (std::getline(instream, line, '\n'))
{
Book newBook;
fillBook(line,newBook);
// add this book to inventory
inventory.push_back(newBook);
}
instream.close();
std::cout<<(to_string(inventory.size()) + " books were successfully added to inventory");
}
// if failed to open the file
else
std::cout<<("Cannot open the file. Make sure the file name is correct");
}
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