将文本文件中的数据读入C++结构

Question

这是一个应该从文本文件中读取书籍清单的程序（对于每本书，文本文件的每一行都按照正确的顺序包含不同的字段）。由于某种原因，例行程序无限期地继续下去。 “eof”错误陷阱似乎无法捕捉文件的结尾。有人可以给我一个想法是什么错？请记住我是C++世界的真正新手，但不是编程的新手。

首先，我已经包含了正确的头文件书

// structure definition 
struct Book 
{ string isbn; 
    string title; 
    string author; 
    string publisher; 
    int quantity; 
    float price; }; 

的结构定义。下面是似乎没有工作的例程。我把一些cout < <“放到第一行”endl;代码来查看例程的进度，并且它只是重复从文本文件中提取数据。该文本文件中只有6本书，所以它应该快速读取文本文件。

非常感谢您的帮助！

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"); 
} 

Answer 1

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"); 
}