How to deal with "'MainWindow' does not refer to a value"?

ddryomyss

Hello y'all,
I get it while trying to connect a signal from MainWindow class to the slot from the SecDialog class. Why I get an error?

mainwindow.h:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

signals:
    void bubaSignal();

private slots:
    void on_pushButton_clicked();

private:
    Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

mainwindow.cpp:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "secdialog.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}


void MainWindow::on_pushButton_clicked()
{
    SecDialog secDialog;
    secDialog.setModal(true);
    emit bubaSignal();
    secDialog.exec();
}

secdialog.h:

#ifndef SECDIALOG_H
#define SECDIALOG_H

#include <QDialog>

namespace Ui {
class SecDialog;
}

class SecDialog : public QDialog
{
    Q_OBJECT

public:
    explicit SecDialog(QWidget *parent = nullptr);
    ~SecDialog();

public slots:
    void dubaSlot();
private:
    Ui::SecDialog *ui;
};

#endif // SECDIALOG_H

secdialog.cpp

#include "secdialog.h"
#include "ui_secdialog.h"

#include "mainwindow.h"

SecDialog::SecDialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::SecDialog)
{
    ui->setupUi(this);
    connect(&MainWindow, SIGNAL(bubaSignal()), this, SLOT(dubaSlot())); <- error is here
}

SecDialog::~SecDialog()
{
    delete ui;
}

void SecDialog::dubaSlot()
{
    ui->label1->setText("duba slot works");
}

JonB

@ddryomyss
MainWindow is a class/type, not an instance. connect() only accepts instances, like the this you have for the slot.

This is the wrong approach anyway. A dialog should never know about any main window. The connect() belongs in the MainWindow class where you create the dialog instance, not in the SecDialog class.

ddryomyss

@JonB said in How to deal with "'MainWindow' does not refer to a value"?:

This is the wrong approach anyway. A dialog should never know about any main window. The connect() belongs in the MainWindow class where you create the dialog instance, not in the SecDialog class.

K, I think I got it. Thanks!

JonB

@ddryomyss
Further.

If you want to use a signal/slot approach here that is doable. However. If all you want to do is the

 ui->label1->setText(...)

I think most people would rather expose a setter method in SecDialog which will set that text. (And potentially a getter method to similarly return it if it were, say, an editable widget.)

    SecDialog secDialog;
    secDialog.setLabel1Text("Some text");
    secDialog.exec();
    auto editableText = secDialog.editWidgetText();

Rather than a signal/slot approach for this. Depends what you're wanting to do.