Facing some problem with global Variable in QT C++ - sqlite

Question

I have a login page and a welcome page (which open if user can bypass the login). In my login page
there is a line edit for entering username. So, for holding the username I declared a global variable in
the login.h.
My login.h file:
#include <QSqlQuery>
#include <QGridLayout>
#include <QPushButton>
#include <QString>
#include <QLabel>
#include <QFrame>
#include <QSqlRecord>
#include <QFileDialog>
#include <QPixmap>
#include <QMessageBox>
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
class login : public Qlogin
{
Q_OBJECT
public:
login(QWidget *parent = nullptr);
~login();
private:
Ui::login *ui;
QString userDat; ///global variable
};
#endif // MAINWINDOW_H
I hold the username from the line edit in login.cpp like this.
My login.cpp file:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QSqlQueryModel>
#include <QSqlQuery>
#include <QGridLayout>
#include <QPushButton>
#include <QString>
#include <QLabel>
#include <QFrame>
#include <QSqlRecord>
#include <QFileDialog>
#include <QPixmap>
#include <QMessageBox>
login::login(QWidget *parent)
: Qlogin(parent)
, ui(new Ui::login)
{
ui->setupUi(this);
userDat = ui-> login_lineEdit ->text();
}
login::~login()
{
delete ui;
}
I want to use the global variable userDat in my welcome.cpp file like this.
ui-> welcome_lineEdit->setText(userDat);
I've included all required header file in welcome.h and welcome.cpp. But it still says:
userDat is not declared in this scope.
please help

Answer 1

Update from comments:
#include <QSqlQuery>
#include <QGridLayout>
#include <QPushButton>
#include <QString>
#include <QLabel>
#include <QFrame>
#include <QSqlRecord>
#include <QFileDialog>
#include <QPixmap>
#include <QMessageBox>
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
class UserData {
public:
static QString userName;
};
class login : public Qlogin
{
Q_OBJECT
public:
login(QWidget *parent = nullptr);
~login();
private:
Ui::login *ui;
};
#endif // MAINWINDOW_H
in login.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QSqlQueryModel>
#include <QSqlQuery>
#include <QGridLayout>
#include <QPushButton>
#include <QString>
#include <QLabel>
#include <QFrame>
#include <QSqlRecord>
#include <QFileDialog>
#include <QPixmap>
#include <QMessageBox>
QString UserData::userName = "empty";
login::login(QWidget *parent)
: Qlogin(parent)
, ui(new Ui::login)
{
ui->setupUi(this);
UserData::userName = ui-> login_lineEdit ->text();
}
login::~login()
{
delete ui;
}
and somethere in another place:
ui-> welcome_lineEdit->setText(UserData::userName);