Elegant way to access objects created in qApplication main function - c++

Question

I want to create a window application with Qt framework and C++, in which an object is created to operate hardware, and should be accessible to MainWindow and all its members and methods. I do not have very much experience of doing things like this.
int main(int argc, char *argv[]) {
QApplication qApp(argc, argv);
CoolHardware *CoolHardware500 = new CoolHardware; // Object that connects to hardware.
CoolHardware500.Connect();
// Show main window here.
MainWindow qApp_Win(CoolHardware500); // This is the only elegant way I could think.
qApp_Win.show();
return qApp.exec();
// Deconstructor.
CoolHardware500>~CoolHardware();
}
In the methods of MainWindow, is not accessible. How to solve this?
void MainWindow::CoolHardwareDoSomething() {
CoolHardware500->DoSomehing(); // Here CoolHardware500 is shown as not defined.
}
Questions:
Is it an elegant way to create an hardware-operating object in the main() function? How to make it accessible to the members/methods of the MainWindow?
Is it better to create objects in the constructor of the MainWindow and deconstruct objects in the MainWindow deconstructor? In this way, accessing object is easy.
If this two ways are both not elegant ways of doing things, what is the elegant way of doing that?
Thank you very much.

Answer 1

MainWindow is subclassing QMainWindow, but it's a regular C++ class, so just store either an instance directly, or a pointer, as a member variable on it.
In MainWindow.h (or .hpp):
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
private:
Ui::MainWindow *ui;
// Either this:
CoolHardware500* m_coolHardwarePtr;
// Or that:
CoolHardware500 m_coolHardware;
};
In the constuctor MainWindow::MainWindow you can pass arguments to the CoolHardware500 ctor as needed, or use a new if you use a pointer.
If using a pointer, you also want to have the destructor MainWindow::~MainWindow do a delete m_coolHardwarePtr;.
You could also use a smart pointer (like std::unique_ptr) to avoid to remember to do that delete yourself.
Mainwindow.cpp, assuming you have a Ctor CoolHardware500::CoolHardware500(int):
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow),
m_coolHardware(1),
m_coolHardwarePtr(new CoolHardware500(1))
{
ui->setupUi(this);
}
MainWindow::~MainWindow()
{
delete ui;
delete m_coolHardwarePtr;
}

Answer 2

Here's how:
struct MainWindow : QMainWindow {
private:
CoolHardware hardware;
// ...
public:
MainWindow() {
hardware.connect();
// ...
}
// use `hardware`
};