从 C++ 中的 txt 文件中读取书籍信息？

Question

我想阅读书籍 - 来自 txt 文件的书名、作者和价格。 The 3 properties of the book are separated by '|' - Title|Author|Book. 但是，我不知道该怎么做。我有结构书，有 3 个元素。我想，对于每一行读取书名、作者和价格，将它们分别保存到结构的 3 个变量中并在控制台上打印它们。我尝试仅使用标题来执行此操作，但它会打印整行。我想问如何为每本书分别打印其作者名称和价格？

Answer 1

您需要的包含库，以及您的Book 结构定义。一旦你开始学习更高级的 C++ 主题，你就可以学习如何为输入和输出流重载友元函数，以使你的 I/O 操作为 Book 对象自包含。

#include <iostream> ///< std::cout
#include <fstream>  ///< std::ifstream
#include <sstream>  ///< std::istringstream, std::string
#include <vector>   ///< std::vector

struct Book
{
    std::string title;  ///< title of the book
    std::string author; ///< author of the book
    std::string price;  ///< price of the book (TODO use float instead?)
    // TODO consider friend std::istream& operator>> for parsing input data
    // TODO consider friend std::ostream & operator<< for printing object
};

如果你有输入文件的句柄，你可以像这样解析它。一次阅读每一行。 Do not read until input.eof() 因为错了！将每一行存储到一个临时的std::istringstream 对象中以供进一步解析。使用重载的std::getline(stream, token, delimiter) 和| 来解析行中的数据，并将它们直接保存到您的临时Book 对象中。最后，如果您希望以后能够处理它们，请将对象存储到您的向量中，并可选择将它们打印到控制台。

void readBooks(std::ifstream& input, std::vector<Book>& books)
{
    std::string line;
    while (std::getline(input, line)) ///< while we have a line to parse
    {
        std::istringstream iss(line); ///< line to parse as sstream
        Book book; ///< temporary book object
        std::getline(iss, book.title, '|');
        std::getline(iss, book.author, '|');
        std::getline(iss, book.price, '|');
        books.push_back(book); ///< add book object into vector
        std::cout << "Title:  " << book.title << std::endl;
        std::cout << "Author: " << book.author << std::endl;
        std::cout << "Price:  " << book.price << std::endl << std::endl;
    }
}

int main()
{
    std::vector<Book> books;  ///< store each Book object
    std::ifstream input("books.txt");
    if (input.is_open())
    {
        readBooks(input, books); ///< read your books
    }
    return 0;
}

使用以下输入文件内容测试

Tales from Shakespeare (1807)|Shakespeare|6.74
The Jungle Book (1894)|Rudyard Kipling|9.99
Through the Looking-Glass (1871)|Lewis Carroll|12.97

得到以下结果

Title:  Tales from Shakespeare (1807)
Author: Shakespeare
Price:  6.74

Title:  The Jungle Book (1894)
Author: Rudyard Kipling
Price:  9.99

Title:  Through the Looking-Glass (1871)
Author: Lewis Carroll
Price:  12.97

Answer 2

#include <iostream>
#include <string>
#include <fstream>
using namespace std;

struct Book {
    string title;
    string author;
    string price;
};
void read_Books(std::ifstream&, Book&);

int main()
{
    ifstream p("books.txt", ios::in);
    Book a;
    read_Books(p, a);
    return 0;
}
void read_Books(std::ifstream& p, Book& ptstr) {
    while(p.is_open() && !p.eof()){
        getline(p, ptstr.title, '|');
        getline(p, ptstr.author, '|');
        getline(p, ptstr.price, '|');
        cout<<ptstr.title << ptstr.author << ptstr.price << std::endl;
        //The whole line is printed, it ought to be the title only
    }
}