QErrorMessage keeps on appearing - c++

Question

I count some entries and want to emit a message, when the user has many entries, since it will be confusing.
Nevertheless the other hand the user should have the option to disable this warning.
That's why I wanted to use a QErrorMessage.
But my QErrorMessage kept on appearing even when it should not (/when the checkbox is unchecked).
This is the shortest code I wrote:
void checkNumber(int const &n)
{
if(n > CriticalNumber)
{
QErrorMessage msg(this);
msg.showMessage("too much!");
}
}
Did I forget anything?
The funny thing is, after you once unchecked the checkbox, it is unchecked in every next call...
// edit:
This error happens even when the QErrorMessage is a member of my class and not initialised in every call.
// edit2:
By now I am pretty sure, that this error only occurs, when I use QString::arg. I did not use this in the example code, since I thought this would make no difference. So the example should look like this:
void showError(int const &n, QErrorMessage *msg)
{
msg->showMessage(tr("%1 is too big").arg(n));
}
showError() is called in the previous if-statement.

Answer 1

I solved this problem (specified in edit2).
The problem is, that the QErrorMessage saves all the QStringsthat should not be shown again.
Since my arg() creates nearly every time a new QStringthe QErrorMessageis shown each time it is changed.
Example:
QErrorMessage msg(this);
showError(1, msg);
showError(2, msg);
showError(1, msg);
The first showError(1, msg) will show the QErrorMessage.
If you uncheck the checkbox, showError(2, msg) will be shown (because a different QString is shown), but not showError(1, msg) (since the shown QString is the same as the first one.

Answer 2

I cannot reproduce your problem. What you should to is make checkNumber a member of a class, and do the same for your msg object.
Here is a working example:
mainwinodw.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QErrorMessage>
#include <QTimer>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
public slots:
void showErrorMsg();
private:
Ui::MainWindow *ui;
QErrorMessage msg;
QTimer timer;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(&timer, SIGNAL(timeout()), this, SLOT(showErrorMsg()));
timer.start(3000); // we use a timer to show an error message
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::showErrorMsg()
{
msg.showMessage("My message");
}