How to regain parent's window functions,after child window has closed

[mekos]

Hello

i have 2 windows,one mainwindow and one dialog.a signal emmited from the mainwindow and the dialog appears.Do something in the dialog and before i close it i have to call a function from the mainwindow to refresh a mainwindow's label.
How can i do that?

example code:



======Class MainWindow========
MainWindow::MainWindow( QWidget * parent, Qt::WFlags f ): QMainWindow( parent, f )
{
setupUi( this );
connect( showBtn, SIGNAL( clicked() ), this, SLOT( showUsers() ) );
}



void MainWindow::showUsers( )
{
//actons etc.etc.
Users *usr;
usr->show();

}


======Class Users========
Users::Users( QWidget * parent ) : QDialog( parent )
{
setupUi(this);
setModal(true);
connect( testButton, SIGNAL( clicked( ) ), this, SLOT(changeSomething( ) ) );
}


void Users::changeSomething( )
{
//actons etc.etc.
and somewhere here i have to use a function from mainwindow
to update something e.g mainwindow->refresh();
}


Can anyone help??

Thanks

[wysota]

What exactly is the problem? Accessing the window's pointer? There are at least two ways to do it, either pass a pointer to the dialog or use QWidget::parentWidget().

[jacek]

If Users is going to be a modal dialog, you can do it this way:

void MainWindow::showUsers( )
{
Users usr;
if( usr.exec() == QDialog::Accepted ) {
changeSomething( usr.getSomething() );
}
}

If it is a modeless dialog, you can use signals & slots mechanism. Just define some signal in the Users class and connect it to proper slot in MainWindow.

Third option is to pass a pointer to MainWindow instance to User, but this isn't good as it introduces tight coupling.

[mekos]

jacek that would be good but the problem is i have a lot of functions in the dialog,it's just one of them which when called then i have to refresh the mainwindow ..the above code was just a mini example.

wysota i tried


void Users::changeSomething( )
{
//actons etc.etc.
QWidget *main=this->parentWidget();
main->(should appear mainwindow's functions here?)

}

[jacek]

the problem is i have a lot of functions in the dialog,it's just one of them which when called then i have to refresh the mainwindow ..
I don't see a problem. Just make it emit a custom signal and connect that signal to a slot in MainWindow.

[mekos]

If i knew how to connect the User class with the mainwindow object, to emit a signal to User to Mainwindow it would be great :D

======Class Users========
Users::Users( QWidget * parent ) : QDialog( parent )
{
setupUi(this);
setModal(true);
connect( testButton, SIGNAL( clicked( ) ), this, SLOT(changeSomething( ) ) );
connect( testButton, SIGNAL( clicked( ) ), MainWindow, SLOT(refresh( ) ) );
}

this is not working..some example code would be great..

correction:
*to emit a signal FROM Users to Mainwindow

[jacek]

If i knew how to connect the User class with the mainwindow object, to emit a signal to User to Mainwindow it would be great :D
First you need to define a custom signal:

class Users : ...
{
Q_OBJECT
...
signals:
void yourSignal();
...
};
then you can emit it:
emit yourSignal();

[wysota]

wysota i tried


void Users::changeSomething( )
{
//actons etc.etc.
QWidget *main=this->parentWidget();
main->(should appear mainwindow's functions here?)

}


Cast the pointer to appropriate class:


QWidget *wgt = parentWidget();
MainWindow *main = qobject_cast<MainWindow*>(wgt);
Q_ASSERT(main!=0);
main->...

[mekos]

Thank you both
i'll try your suggestions..hope i find it eventually :)

[mekos]

I'm afraid Users is not child of Mainwindow..
Q_ASSERT(main!=0) fails.
debugger output:
Cannot access memory at address 0x0
and the variable parent is 0x0..
do i have to set that the Users dialog is child of MainWindow?



void MainWindow::showUsers( )
{
//actons etc.etc.
Users *usr;
usr->show();
//declare that usr is child somewhere here? how?
}


Or maybe i have created the two constructors the wrong way so and i'll never figure out something

[mekos]

ok finally
done it with the other way



Users *usr;
if( usr->exec() ) {
usr->changeSomething() );
}


thank you both:)

[wysota]

If usr is a dialog, you can pass a parent to it when creating it. Currently you have a modal dialog without pointing which window should be blocked until you close the dialog.