如何在C ++中验证文件中的用户登录名？

Question

我正在尝试创建一个简单的程序，请求用户注册并将记录保存到文件中，如果用户已经注册，则可以通过其用户名和密码登录。但是问题是我如何验证records.txt文件中是否已经存在用户名和密码？他们是正确的吗？因此用户可以登录。我已经尝试了很多方法，但是我无法使其正常工作。我是一名大学生。

这是我的代码。

#include <stdio.h>
#include <conio.h>
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int main() {
string uName, pass, name, email, gender;
string logname, logpass;
string valname, valpass;
int phone;
ofstream output;
output.open("record.txt");
cout<<"Enter username: "<<endl;
cin>>uName;
cout<<"Enter password: "<<endl;
cin>>pass;
cout<<"Enter name: "<<endl;
cin>>name;
cout<<"Enter email: "<<endl;
cin>>email;
cout<<"Enter gender: "<<endl;
cin>>gender;
cout<<"Enter phone number: "<<endl;
cin>>phone;

output<<uName<<" "<<pass<<" "<<name<<" "<<email<<" "<<gender<<" "<<phone<<endl;
output.close();
cout<<"Registration complete!"<<endl;


//  login
ifstream input("record.txt");

cout<<"Enter username:"<<endl;
cin>>logname;
cout<<"Enter password:"<<endl;
cin>>logpass;

if((input>>uName)==logname && (input>>pass)==logpass) { 
//input>>uName trying to get to the file and 
//read the already entered uName and match with the current entered name by user, same with pass
    cout>>"Login successful"<<endl;
}
else {
    cout<<"Login failed!"<<endl;
}

input.close();
cout<<"Done!"<<endl;

return 0;

}

编辑：我无法登录。这是编译日志：

https://pastebin.com/FmWizEtr

超出字数限制。

编辑2：如果删除我的登录代码，这是我的record.txt文件：

john666 qwertyui John [email protected] Male 682739658

任何帮助将不胜感激。谢谢

编辑3：非常感谢THANKYOU在这里的工作代码（稍有变化）：

#include <stdio.h>
#include <conio.h>
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int main() {
    string uName, pass, name, email, gender;
    string logname, logpass;
    string valname, valpass;
    int phone;
    int choice;
    cout<<"Enter choice:"<<endl;
    cout<<"1.Register\t\t2.Login"<<endl;
    cin>>choice;

    if (choice==1) {
        ofstream output;
        output.open("record.txt");
        cout<<"Enter username: "<<endl;
        cin>>uName;
        cout<<"Enter password: "<<endl;
        cin>>pass;
        cout<<"Enter name: "<<endl;
        cin>>name;
        cout<<"Enter email: "<<endl;
        cin>>email;
        cout<<"Enter gender: "<<endl;
        cin>>gender;
        cout<<"Enter phone number: "<<endl;
        cin>>phone;

        output<<uName<<" "<<pass<<" "<<name<<" "<<email<<" "<<gender<<" "<<phone<<endl;
        output.close();
        cout<<"Registration complete!"<<endl;

    }
    else if(choice==2){
        //  login
        ifstream input("record.txt");

        if(!input) {
            cout<<"Error creating file!";
        }

        cout<<"Enter username:"<<endl;
        cin>>logname;
        cout<<"Enter password:"<<endl;
        cin>>logpass;

        if (input >> uName && input >> pass &&     // check if reading was successfull
        uName == logname && pass == logpass) { //input??uName trying to get to the file and read the already entered uName and match with the current entered name by user, same with pass
            cout<<"Login successful"<<endl;


        }
        else {
            cout<<"Login failed!"<<endl;
        }

        input.close();
        cout<<"Done!"<<endl;
    }
    else {
        cout<<"Please enter a valid choice!"<<endl;
    }

    return 0;

   }

Answer 1

您的主要问题是这条线

if((input>>uName)==logname && (input>>pass)==logpass)

您混合使用了两种设计样式。如您在documentation中看到的，std::basic_istream::operator>>的所有重载都返回basic_istream &。

这意味着input>>uName返回对input的引用，您无法将其与std::string进行比较。正确的模式如下：

if (input >> uName && input >> pass &&     // check if reading was successfull
    uName == logname && pass == logpass)   // check if the read data matches the input

---

另一个问题是

cout>>"Login successful"<<endl;

这只是一个错字，必须是

cout<<"Login successful"<<endl;

---

最后一点，您应该始终检查流是否已成功打开：

    ifstream input("record.txt");

    if(!input) { /* error occurred while opening */ }