QMessageBox and QFileDialog in a loop - c++

Question

I have a program that needs to check at startup if a path to project is set. For that I have subclassed QMessageBox, added some custom stuff (like spacer to make dialog wider) and I am calling QFileDialog::getExistingDirectory to get directory.
Thing is, user can click Cancel in QFileDialog. But I want user to be returned to QMessageBox to have another chance to set path or quit program altogether. To achieve that I wrote method loop():
CustomMessageBox::loop()
{
while (true) {
this->exec();
if (this->clickedButton() == setPathButton) {
path = QFileDialog::getExistingDirectory(...);
if (!path.isEmpty()) { break; }
} else if (this->clickedButton() == quitButton) {
break;
}
}
}
Then, I have a method getPath():
CustomMessageBox::getPath()
{
loop();
return path;
}
which I call in main.cpp:
CustomMessageBox box;
QString path = box.getPath();
if (!path.isEmpty()) {
// save path, bla, bla
} else {
exit(EXIT_FAILURE)
}
This works, but is this a good practice? I am specifically asking regarding this while inside which resides method exec().

Answer 1

IMO disadvantages of your decision:
Non-standard usage of dialog class. Put strange loop inside some GUI method and call standard exec() method inside it, when the method can easily be called in a standard way.
Hide exec() call from "user" (another programmer)
Dual, or even triple, purpose of the one getPath() method:
show dialog
flag that the dialog was accepted/rejected via empty - non-empty string
return directory path string
I suggest inherit QDialog (why message box?):
In Degister I put on form standard Push Button setPathButton and Dialog Button Box buttonBox. Then I removed "Ok" button from the box:
#include <QtWidgets/QDialog>
#include "ui_CustomDialog.h"
class CustomDialog : public QDialog
{
Q_OBJECT
public:
CustomDialog(QWidget *parent = nullptr);
QString path() const { return m_path; };
private slots:
void on_setPathButton_clicked();
void on_buttonBox_rejected(); // You can use any pushButton instead: on_closeButton_clicked()
private:
Ui::CustomDialogClass ui;
QString m_path;
};
...
#include "CustomDialog.h"
#include <QFileDialog>
CustomDialog::CustomDialog(QWidget *parent)
: QDialog(parent)
{
ui.setupUi(this);
}
void CustomDialog::on_setPathButton_clicked()
{
m_path.clear();
QString dir = QFileDialog::getExistingDirectory();
if (!dir.isEmpty())
{
m_path = dir;
done(QDialog::Accepted);
}
}
// You can use any pushButton instead: void on_closeButton_clicked()
void CustomDialog::on_buttonBox_rejected()
{
reject();
}
main.cpp
#include "CustomDialog.h"
#include <QtWidgets/QApplication>
#include <QDebug>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
CustomDialog box;
int code = box.exec();
if (code == QDialog::Accepted)
{
qDebug() << box.path();
// save path, bla, bla
}
else
{
exit(EXIT_FAILURE);
}
return a.exec();
}