What should my function be a member of in Qt? - c++

Question

I'm making a simple GUI with Qt Creator.
I'm trying to make an 'openFile' function in the mainwindow.cpp file, but I don't know whether to make this function a member of the mainwindow itself, a separate static function, or a member of a widget.
This function is simple really, it just calls a QFileDialog, gets the path to a file, and opens it, like every open file command on the menu bar you've ever seen.
Now here's the major problem I am having. I tried making this function a member of mainwindow so that I can access ui elements from within the function with ui->QTableWidget for instance, but I can't properly connect the signal to the slot if I do that. I get a whole slew of errors, because in order to do that I need a reference to the mainwindow since connect has the syntax connect(sender, signal, receiver, slot)
I then resorted to making the function separate on its own, but then it has no access to any of the ui elements.
How should I resolve this problem?
EDIT
Here is what I am doing in the constructor.
//Constructor
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QObject::connect(ui->actionOpen, &QAction::triggered, *parent, &MainWindow::openFile);
ui->tableWidget->setColumnCount(16);
}
Here is the resulting error:
C:\workspace\audioPipe\audioPipe\mainwindow.cpp:76: error: C2664: 'QMetaObject::Connection QObject::connect<void(__cdecl QAction::* )(bool),void(__cdecl MainWindow::* )(void)>(const QAction *,Func1,const MainWindow *,Func2,Qt::ConnectionType)' : cannot convert parameter 3 from 'QWidget' to 'const MainWindow *'
with
[
Func1=void (__cdecl QAction::* )(bool),
Func2=void (__cdecl MainWindow::* )(void)
]
No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

Answer 1

The compiler is telling you that as a third parameter to connect(), it expects a pointer to a MainWindow, i.e. a const MainWindow *. You however pass *parent, which is of type QWidget. Furthermore, parent is the wrong object anyway, since that is the parent of the MainWindow object, however you want to pass the MainWindow object itself - and that is this.
So something like the following should work:
QObject::connect(ui->actionOpen, &QAction::triggered, this, &MainWindow::openFile);