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();
}

======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();
}

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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() );
   }
}

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

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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?)
 
}

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

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[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

======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

First you need to define a custom signal:

class Users : ...
{
   Q_OBJECT
   ...
   signals:
       void yourSignal();
   ...
};

class Users : ...
{
   Q_OBJECT
   ...
   signals:
       void yourSignal();
   ...
};

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then you can emit it:

emit yourSignal();

emit yourSignal();

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[wysota]

wysota i tried

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

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

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Cast the pointer to appropriate class:

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

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

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[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?
}

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

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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() );
   }

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

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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.