How to use Qt classes defined accross multiple files?

[MakingTheEight]

I'm trying to create my first Qt desktop application. I have managed to create a QMainWindow widget and I am trying to add a menu bar to it. I was able to create a MainWindow with a menu bar that has one menu option. I was able to do this when all my code was in one file, and I was using the MainWindow constructor to set up the whole GUI.

I now would like to separate my GUI/widgets into separate files for maintainability.
Here are my current files:
mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "filesystem.h"

#include "./menu/filemenu.h"

class QString;

class FileMenu;

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow {
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);

    ~MainWindow();

private:
    Ui::MainWindow *ui;
    QString main_title = "";

    int width;
    int height;

    FileMenu *filemenu;

    void setName() {
        this->setWindowTitle(MainWindow::main_title);
    };

    void resizeMainWindow();
    void setUp();

    // void createMenuBar();


};

#endif

mainwindow.cpp

#include <stdlib.h>
#include <QtWidgets>
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDesktopWidget>
#include <QRect>



MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent), ui(new Ui::MainWindow) {
    ui->setupUi(this);
    this->setUp();
    filemenu = new FileMenu(this);
    filemenu->createMenuBar();
}

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

void MainWindow::resizeMainWindow() {
    QRect main_screen = 
   QDesktopWidget().availableGeometry(QDesktopWidget().primaryScreen());
    MainWindow::height = main_screen.height();
    MainWindow::width = main_screen.width();
    this->resize(MainWindow::width, MainWindow::height);
}

void MainWindow::setUp() {
    this->setName();
    this->resizeMainWindow();
}

./menu/filemenu.h

#ifndef FILEMENU_H
#define FILEMENU_H

#include <QMenu>
#include <QAction>
#include <QMenuBar>

#include "../mainwindow.h"

class MainWindow;
class QMenu;
class QMenuBar;

class FileMenu: public QMainWindow {
    Q_OBJECT

    public:
        FileMenu(MainWindow *p);
        ~FileMenu();
        void createMenuBar();

    private:
        MainWindow *parent;

        QMenu *fileOption;
        QAction *newFolder;
        QAction *newFile;
        QAction *newWindow;
        QAction *exitWindow;

        void createFileActions();
    private slots:
        void openNewFolder();
        void openNewWindow();
        void openNewFile();
        void exitWindow();
};

#endif

./menu/filemenu.cpp

#include "filemenu.h"
#include <QMainWindow>

FileMenu::FileMenu(MainWindow *p):
    parent(p) {
    //this->createMenuBar();
    this->createFileActions();

}

void FileMenu::createMenuBar() {
    fileOption = menuBar()->addMenu(tr("&File"));
    fileOption->addAction(newWindow);
    fileOption->addAction(newFolder);
    fileOption->addAction(newFile);
}


void FileMenu::createFileActions() {
    newFolder = new QAction(tr("&New Folder"), this);
    newFolder->setShortcut(tr("Ctrl+Shift+N"));
    newFolder->setStatusTip(tr("Create a new folder"));
    connect(newFolder, &QAction::triggered, this, &FileMenu::openNewFolder);

    newWindow = new QAction(tr("&New Window"), this);
    newWindow->setShortcut(tr("Ctrl+N"));
    newWindow->setStatusTip("Open a new MTX window");
    connect(newWindow,&QAction::triggered, this, &FileMenu::openNewWindow);

    newFile = new QAction(tr("&New File"), this);
    newFile->setShortcut(tr("Shift+N"));
    newFile->setStatusTip("Create a new file");
    connect(newFile, &QAction::triggered, this, &FileMenu::openNewFile);

    exitWindow = new QAction(tr("&Exit"), this);
    exitWindow->setShortcut(tr("Shift+C"));
    exitWindow->setStatusTip("Exit MTX");
    connect(exitWindow, &QAction::triggered, this, &FileMenu::openNewFile);
}
void FileMenu::exitWindow() {
    exit(EXIT_SUCCESS);
}


FileMenu::~FileMenu() {
    delete newFolder;
    delete newFile;
    delete newWindow;
    delete exitWindow;
}

However, when I make and run the project when it's structured as above, the main window loads with no menu. What am I doing wrong?

Thanks for the help.

[SGaist]

Hi and welcome to devnet,

Because you're not looking at the main window you expect. You did not really separate things here actually, you created a separate QMainWindow based class that you put in the main QMainWindow based class but you don't show it.

[MakingTheEight]

@SGaist Can you expound on this statement? I'm not sure I understand it exactly as you've phrased it.

You did not really separate things here actually, you created a separate QMainWindow based class that you put in the main QMainWindow based class but you don't show it.

Thanks.

[mrjj]

@MakingTheEight
Hi
In the old Mainwindow, you do

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent), ui(new Ui::MainWindow) {
ui->setupUi(this);
this->setUp();
filemenu = new FileMenu(this); // new main window
filemenu->createMenuBar();
}

But you do not see FileMenu, but the MainWindow ( i assume).

Please try 

filemenu = new FileMenu(); // new main window dont give parent
filemenu->createMenuBar();
filemenu->show();

You should see you actually have 2 MainWindows :)

I assume you want to use FileMenu as the new MainWindow ?

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    a.setStyleSheet( yourstylesheet );
    MainWindow w; // use FileMenu here instead
    w.show();

    return a.exec();
}

[jsulm]

@MakingTheEight

class MainWindow : public QMainWindow {
...
class FileMenu: public QMainWindow {

Do you realise that you create TWO QMainWindows?
Why is FileMenu derived from QMainWindow?

[MakingTheEight]

@jsulm I have tried to have FileMenu inherit from QMenu but I get the following error.
error: ‘menuBar’ was not declared in this scope.

My idea was to have FileMenu inherit QMenu from QMainWindow. How would you suggest I solve my problem.

Thanks for the hel

[SGaist]

Remove the use of menuBar from it and pass the FileMenu instance to your MainWindow status bar.

[MakingTheEight]

@jsulm @mrjj @ig Thanks for all the help.
I was able to fix the inheritance issue by creating a new FileMenu instance in the main window.