如何遍历文本文件中的行并将其与其他行进行比较（C++）

Question

我创建了一个简单的登录/注册程序，可以读取和写入文件。它要求登录或注册，如果您选择注册，它会使用凭据（用户名和密码）写入单独的文本文件。如果您选择登录，它应该将您的凭据与文件中的所有凭据进行比较，并判断它是否是有效帐户。

这是代码（我知道的时间太长了；我只有 13 岁，所以我有点不擅长）：

#include <iostream>
#include <vector>
#include <fstream>

using namespace std;

// Function that gets username and password from the user
vector<string> askForCredentials(){
    string username, password;

    cout << "Please enter a username: ";
    getline(cin, username);
    // Repeatedly asks the question until the input has no spaces
    while(username.find(" ") != string::npos){
        cout << "No spaces in the username!" << endl;
        cout << "Please enter a username: ";
        getline(cin, username);
    }

    //Again
    cout << "Please enter a password: ";
    getline(cin, password);
    while(password.find(" ") != string::npos){
        cout << "No spaces in the password!" << endl;
        cout << "Please enter a password: ";
        getline(cin, password);
    }

    return {username, password};
}

int main() {
    //Declares variable for user input
    string request;
    cout << "Would you like to log in or sign up? ";
    getline(cin, request);

    //While the input is not log in or sign up it repeats the question
    while(request != "log in" && request != "sign up"){
        cout << "That is not a valid answer. Would you like to log in or sign up? ";
        getline(cin, request);
    }

    //If the user wants to sign up...
    if(request == "sign up"){
        //Creates a vector calling the askForCredentials function which asks user for username and password
        vector<string> credentials = askForCredentials();
        //Opens accounts text file in append mode
        ofstream accounts("current_accounts.txt", ios::app);

        //If the file opens than say account created successfully, otherwise say couldn't make account
        if(!accounts.is_open()){
            cerr << "Couldn't create account" << endl;
            return 0;
        } else{
            cout << "Account created successfully!" << endl;
        }

        //Appends username and password seperated by a space in the accounts file
        accounts << credentials[0] << " " << credentials[1] << " " << endl;
        accounts.close();
    }

    //If the user requests to log in...
    if(request == "log in"){
        //Creates vector with user input and says if file opens successfully or not
        vector<string> credentials = askForCredentials();
        ifstream accounts;
        accounts.open("current_accounts.txt");
        if(!accounts.is_open()){
            cerr << "Couldn't log in" << endl;
            return 0;
        }

    // Need help here

    return 0;
    }
}

我的问题部分在于日志。我基本上需要遍历 current_accounts 文件中的每一行凭据并将其与输入的凭据进行比较。如果有人可以帮助我解决这个问题，将不胜感激！如果您需要更多信息，我也可以回复。

哦，如果你能告诉我如何优化但保持可读性，我将不胜感激。

Answer 1

您可以将以下语句添加到您的软件中：

        if (!accounts.is_open()) {
            cerr << "Couldn't log in" << endl;
            return 0;
        }
        else {

            // Here we will store the status. Did we find the username and password or not
            bool found = false;

            // Temporary storage for username and password read from file
            std::string userName;
            std::string passWord;

            // In a loop, read all usernames and password
            while ((accounts >> userName >> passWord) and not found) {

                // Check, if the data is present
                if ((credentials[0] == userName) and (credentials[1] == passWord)) {

                    // If yes, indicate that and stop the loop
                    found = true;
                }
            }
            // Show result
            if (found) std::cout << "\nLogin successfull\n\n";


        }

这里我们循环读取文件中的所有数据，并与输入的数据进行比较。

提取运算符 >> 将跳过所有空格，因此阅读起来很容易。

这会起作用，因为您不允许在用户名和密码中包含空格。

您还可以使用std::getline 在循环中读取完整的行，将行放入std::istringstream 并从那里提取。这通常是推荐的方法，但在您的情况下不是必需的。

而且您的代码非常好。尤其是很多cmet真的很不错。

在设计方面，我建议将用户名和密码存储在结构中，而不是字符串向量中。