Using object directly from another class c++ - c++

Question

Hi i have 3 classes that i want to use. but i dont want to create object of one class more than once. I directly want to use the object (in third class) of one class declared and initialized in second class.
To understand the problem please focus on NetworkConnection members and class defined in example below.
Class Mainwindow header
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include "secondscreen.h"
#include "networkconnection.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = nullptr);
~MainWindow();
NetworkConnection *NetworkConnectionObject;
private slots:
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
SecondScreen* SecondScreenObject;
};
#endif // MAINWINDOW_H
Class Main Window cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "QMessageBox"
#include "networkconnection.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
NetworkConnectionObject = new NetworkConnection();
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
int Error = NetworkConnectionObject->Connect(Username,Password);
///////////////
// This Works
//////////////
NetworkConnectionObject->LogInToken = "";
}
Class NetworkConnection Header
#ifndef NETWORKCONNECTION_H
#define NETWORKCONNECTION_H
#include <QString>
class NetworkConnection
{
public:
NetworkConnection();
int Connect(QString Username, QString Passwd);
QString LogInToken;
};
#endif // NETWORKCONNECTION_H
Now i want to use Networkclassobject directly in SeconScreenclass so that i can access LogInToken Member of MainWindowInstance.
#include "secondscreen.h"
#include "ui_secondscreen.h"
#include "mainwindow.cpp"
SecondScreen::SecondScreen(QWidget *parent) :
QDialog(parent),
ui(new Ui::SecondScreen)
{
ui->setupUi(this);
///////////////
// This doesnot work
//////////////
MainWindow::NetworkConnectionObject->LogInToken = "";
}
SecondScreen::~SecondScreen()
{
delete ui;
}
However, when i try this compiler says
Invalid use of non-static data member "MainWindow::NetworkConnectionObject" Problem is i dont want to declare it static. Is there any way to do it.

Answer 1

Without seeing secondscreen.h I can't say for sure but MainWindow::NetworkConnectionObject" doesn't reference a specific instance of MainWindow class, you must reference a specific instance to modify.
If in your SecondScreen header you have something like
class SecondScreen {
// . . .
MainWindow window;
// . . .
}
then in your constructor for SecondScreen you must use the initialized instance of MainWindow, i.e.
SecondScreen::SecondScreen(QWidget* parent) : QDialog(parent) {
window.NetworkConnectionObject->LogInToken = "";
}