I was trying to make a login and registration. i am saving the credencials on text file, and for the login i use a if statement to compare what the user typed and the credencials saved on the file. But my if is not working, the program crashes when it "enter". currently my if is inside the while loop for the read file. when i tryed to use it outside the QString username and QString password it was saying they where not declared. here is the code:

        void MainWindow::on_pushButton_Login_clicked()
{
    QString usernamelogin = ui->lineEdit_username->text();
    QString passwordlogin = ui->lineEdit_password->text();

    QFile file("C:/Users/luisp/Desktop/poo/janela_de_login/Credencials/UsersInfo.txt");

     if(!file.open(QFile::ReadOnly | QFile::Text)){
        // QMessageBox::Warning(this,"Aviso", "file not open");
     }
    
     QTextStream in(&file);


while(!in.atEnd())
{
    QString line = in.readLine();
    QStringList credencials = line.split("\n");
    QString username = credencials[1];
    QString password = credencials[2];
    file.flush();
    file.close();

    if (username == usernamelogin && password == passwordlogin){
        //QMessageBox::information(this, "Login", "Username and password correct");
        ui->statusbar-> showMessage("Username e password correct", 3000);
    }
    else{
        //QMessageBox:: warning(this, "Login","Username e password not correct");
         ui->statusbar-> showMessage("Username e password not correct", 3000);
    }

}
}


void MainWindow::on_pushButton_Register_clicked()
{
    QFile file("C:/Users/luisp/Desktop/poo/janela_de_login/Credenciais/UsersInfo.txt");

    if(!file.open(QFile::WriteOnly | QFile::Text)){
       // QMessageBox::Warning(this,"warning", "file not open");
    }

    QTextStream out(&file);
    QString email = ui->Email_Register->text();
    out << email << '\n';
    QString username = ui->Username_Register->text();
    out << username << '\n';
    QString password = ui->Password_Register->text();
    out << password << '\n';

    file.flush();
    file.close();

}

CodePudding user response：

There are a couple of problems I see, '\n' typically indicates a new line so is your username and password on different lines in the file? If not then obviously your problem is they are not on the same line. If you for some odd reason have username\npassword\n all in the same line, then you quite possibly are running off the end of the array returned by QString.split('\n') as it should return them in credentials[0] and credentials[1].

CodePudding user response：

You're wronging assuming that line.split("\n") call returns a list of 3 strings. It's impossible.

Your call in.readLine() read the file till a trailing end-of-line character, and return the string without including the latter.

You are using an end-of-line character for store user credentials, this means that you are reading only one property of the user, and the split function return simply the read text row (the size of the QStringList var is equal to 1)

You can use the readAll() function instead

void MainWindow::on_pushButton_Login_clicked()
{
   QString usernamelogin = ui->lineEdit_username->text();
   QString passwordlogin = ui->lineEdit_password->text();

   QFile file("C:/Users/luisp/Desktop/poo/janela_de_login/Credencials/UsersInfo.txt");

   if(!file.open(QFile::ReadOnly | QFile::Text))
       return;
    
   QTextStream in(&file);
   QStringList userData = in.readAll().split("\n");
   if(userData.size() !== 3)
      return;

   QString userName = userData.at(1);
   QString userPass = userData.at(2);

   ...
}