How to create custom slot in Qt Designer 4.1?

[GreyGeek]

Ouch. I am totally new to Qt and C++ programming. (I knew a little C, but that was a long time ago. Isn't Qt 4 so friendly to start learning Qt?) I have submitted a bug to Trolltech asking them to give me us a Quick Start guide to Designer in Qt 4, but till then how do I learn Qt?

Like you are trying to do, I learned both QT4 and C++ at the same time.
It's not that hard.
For example, you declare a slot in your app.h file:

private slots:
...
	void searchAll();

private slots:
...
	void searchAll();

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Then you put a connection in the constructor of your app class, in app.cpp:

connect(ui.btnSearch, SIGNAL(clicked()), this, SLOT(searchAll()));

connect(ui.btnSearch, SIGNAL(clicked()), this, SLOT(searchAll()));

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and, you put the function in app.cpp, outside the constuctor:

void app::searchAll() {
	// user enters value to search for in search text box
        ....

void app::searchAll() {
	// user enters value to search for in search text box
        ....

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[cioannou]

For example, you declare a slot in your app.h file:

private slots:
...
	void searchAll();

private slots:
...
	void searchAll();

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That's exactly what I am trying to avoid.
If I change the app.h that is generated by the designer and afterwards add some new widgets to my dialog, all my private slots will be lost.

Am I missing something?

[jacek]

If I change the app.h that is generated by the designer and afterwards add some new widgets to my dialog, all my private slots will be lost.

Don't touch those files and instead create another class. You can find the exact instructions here, but in short you need something like this:

#include <QDialog>
#include "ui_somedialog.h" // this file was made from somedialog.ui by uic
 
class SomeDialog : public QDialog
{
   Q_OBJECT
   public:
      SomeDialog( QWidget *parent = 0 );
 
   private slots:
      void searchAll();
 
   private:
      Ui::SomeDialog _ui;
};
 
// .cpp file:
 
void SomeDialog( QWidget *parent ) : QDialog( parent )
{
   _ui.setupUi( this );
   // ...
}
 
void SomeDialog::searchAll()
{
   // ...
}

#include <QDialog>
#include "ui_somedialog.h" // this file was made from somedialog.ui by uic

class SomeDialog : public QDialog
{
   Q_OBJECT
   public:
      SomeDialog( QWidget *parent = 0 );

   private slots:
      void searchAll();

   private:
      Ui::SomeDialog _ui;
};

// .cpp file:

void SomeDialog( QWidget *parent ) : QDialog( parent )
{
   _ui.setupUi( this );
   // ...
}

void SomeDialog::searchAll()
{
   // ...
}

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[GreyGeek]

OK, here are some excepts of my Homestead app that do what I believe you want to do. This code throws up a dialog which contains a list of wholenames selected from a SQL select of type form "LIKE partialname%". Clicking on the proprty_id column and/or the ssn column selects that property or that individual. Clicking the OK or Cancel button closes the dialog.

Here is the wholenamedlg.h header file:

#ifndef WHOLENAMEDLG_H
#define WHOLENAMEDLG_H
.... snip includes ..........
 
#include "ui_wholenamedlg.h"
 
 
class wholenamedlg : public QDialog
{
    Q_OBJECT
 
public:
	wholenamedlg(QWidget *parent = 0, QString partName = "", QString strYear = "2006", QString strSpouseFlag = "F");
	QString resultSSN;
	QString resultPropID;
	QTableView wholeNameView;
 
private:
	Ui::wholeNameDlgUI wnui;
 
private slots:
	void copyVALUES(const QModelIndex &);
 
};
 
#endif

#ifndef WHOLENAMEDLG_H
#define WHOLENAMEDLG_H
.... snip includes ..........

#include "ui_wholenamedlg.h"


class wholenamedlg : public QDialog
{
    Q_OBJECT

public:
	wholenamedlg(QWidget *parent = 0, QString partName = "", QString strYear = "2006", QString strSpouseFlag = "F");
	QString resultSSN;
	QString resultPropID;
	QTableView wholeNameView;

private:
	Ui::wholeNameDlgUI wnui;

private slots:
	void copyVALUES(const QModelIndex &);

};

#endif

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"wholeNameDlgUI" is the name given to the dialog during the Designer session.


Here is the wholenamedlg.cpp file which displays the dialog grid:

/*
Program:		wholenamedlg.cpp
Description:	A dialog class for picking an SSN and/or a name out of 
		a query  created by the SQL LIKE % syntax.
Author:			Jerry L Kreps
Date:			11/10/05 - ff
*/
 
#include "wholenamedlg.h"
... snip includes ......
 
wholenamedlg::wholenamedlg(QWidget *parent, QString partName, QString strYear, QString strSpouseFlag)
: QDialog(parent)  
{
	wnui.setupUi(this);
 
	connect(this->wnui.wholeNameView,	SIGNAL(clicked(QModelIndex)),	this,	SLOT(copyVALUES( QModelIndex )));
 
	partName.prepend("'");
	partName.append("'");
	QString queryStr = "SELECT proprty_id,ssn,wholename,sssn,sname,city,address FROM persinfo_";
	queryStr.append(strYear);
	if (strSpouseFlag == "F") {
		queryStr.append(" WHERE wholename LIKE ");
		queryStr.append(partName);
		queryStr.append(" ORDER BY wholename");
	} else {
		queryStr.append(" WHERE sname LIKE ");
		queryStr.append(partName);
		queryStr.append(" ORDER BY sname");	
	}
	QSqlQueryModel *viewModel = new QSqlQueryModel(wnui.wholeNameView);
	viewModel->setHeaderData(0, Qt::Horizontal, "ID");
	viewModel->setHeaderData(1, Qt::Horizontal, "SSN");
	viewModel->setHeaderData(2, Qt::Horizontal, "WholeName");
	viewModel->setHeaderData(3, Qt::Horizontal, "SSSN");
	viewModel->setHeaderData(4, Qt::Horizontal, "SName");
	viewModel->setHeaderData(5, Qt::Horizontal, "City");
	viewModel->setHeaderData(6, Qt::Horizontal, "Address");
 
	viewModel->setQuery(queryStr);
	if (viewModel->lastError().type() == QSqlError::NoError){
		wnui.wholeNameView->setModel(viewModel);
		if (viewModel->rowCount() > 0){
			for (int i = 0; i < viewModel->rowCount(); ++i)
				this->wnui.wholeNameView->verticalHeader()->resizeSection(i,20);
			for (int i = 0; i < 7; ++i)
				wnui.wholeNameView->resizeColumnToContents(i);
		}
	}
}
 
void wholenamedlg::copyVALUES(const QModelIndex &QMI) {
	QVariant value = this->wnui.wholeNameView->model()->data(QMI,0);
	if (value.isValid()) {
		if (QMI.column() == 0)
			this->resultPropID =  value.toString();
		if (QMI.column() == 1)
			this->resultSSN =  value.toString();	
	}
}

/*
Program:		wholenamedlg.cpp
Description:	A dialog class for picking an SSN and/or a name out of 
		a query  created by the SQL LIKE % syntax.
Author:			Jerry L Kreps
Date:			11/10/05 - ff
*/

#include "wholenamedlg.h"
... snip includes ......

wholenamedlg::wholenamedlg(QWidget *parent, QString partName, QString strYear, QString strSpouseFlag)
: QDialog(parent)  
{
	wnui.setupUi(this);

	connect(this->wnui.wholeNameView,	SIGNAL(clicked(QModelIndex)),	this,	SLOT(copyVALUES( QModelIndex )));
	
	partName.prepend("'");
	partName.append("'");
	QString queryStr = "SELECT proprty_id,ssn,wholename,sssn,sname,city,address FROM persinfo_";
	queryStr.append(strYear);
	if (strSpouseFlag == "F") {
		queryStr.append(" WHERE wholename LIKE ");
		queryStr.append(partName);
		queryStr.append(" ORDER BY wholename");
	} else {
		queryStr.append(" WHERE sname LIKE ");
		queryStr.append(partName);
		queryStr.append(" ORDER BY sname");	
	}
	QSqlQueryModel *viewModel = new QSqlQueryModel(wnui.wholeNameView);
	viewModel->setHeaderData(0, Qt::Horizontal, "ID");
	viewModel->setHeaderData(1, Qt::Horizontal, "SSN");
	viewModel->setHeaderData(2, Qt::Horizontal, "WholeName");
	viewModel->setHeaderData(3, Qt::Horizontal, "SSSN");
	viewModel->setHeaderData(4, Qt::Horizontal, "SName");
	viewModel->setHeaderData(5, Qt::Horizontal, "City");
	viewModel->setHeaderData(6, Qt::Horizontal, "Address");
	
	viewModel->setQuery(queryStr);
	if (viewModel->lastError().type() == QSqlError::NoError){
		wnui.wholeNameView->setModel(viewModel);
		if (viewModel->rowCount() > 0){
			for (int i = 0; i < viewModel->rowCount(); ++i)
				this->wnui.wholeNameView->verticalHeader()->resizeSection(i,20);
			for (int i = 0; i < 7; ++i)
				wnui.wholeNameView->resizeColumnToContents(i);
		}
	}
}

void wholenamedlg::copyVALUES(const QModelIndex &QMI) {
	QVariant value = this->wnui.wholeNameView->model()->data(QMI,0);
	if (value.isValid()) {
		if (QMI.column() == 0)
			this->resultPropID =  value.toString();
		if (QMI.column() == 1)
			this->resultSSN =  value.toString();	
	}
}

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"wholeNameView" is the name given in the Designer to the tableview grid containing the data being displayed.

Here is the main class for the homestead application. The segment shown displays that part of the searchALL() function which calls the wholenamedlg dialog.

/*
Program:	homestead.cpp
Description:	Homestead Application Program (HAP)
Author:		Jerry L Kreps
Date:		11/1/2005
*/
#include "homestead.h"
#include "wholenamedlg.h"
...
homestead::homestead(QWidget *parent) : QMainWindow(parent) {
	// homestead constructor method
	ui.setupUi(this);  // draw the gui interface
	this->Year65 = 1940;  // set birth year for 65 year olds
	this->dbYear = "2006";
...
 
	connect(ui.btnSearch, SIGNAL(clicked()), this, SLOT(searchAll()));
...
...
} // end of the homestead constructor
 
void homestead::searchAll() {
	// user enters value to search for in search text box
	// and clicks the radio button indicating its data type
        // then clicks the search button
	bool foundProp = false;
	bool foundPers = false;
	QString queryStr = "";
	QString seekWN = "'";  // set up for possible wholename search
	QString requestString;
	requestString = "Searching for: ";
	requestString.append(ui.leSearch->text()); // echo search request
	if (ui.rbWholeName->isChecked()) {
		QString partialName = ui.leSearch->text().trimmed();
		if (partialName.contains('%')){
			//select proprty_id,ssn,wholename,sssn,sname,city,address from persinfo_2006
			//WHERE wholename LIKE 'MILLER/E%'  ORDER BY wholename
			wholenamedlg dlg(this, partialName, this->dbYear, "F");
			if( dlg.exec() == QDialog::Accepted ){
				QString strSSN = dlg.resultSSN.trimmed();
				QString strPropID = dlg.resultPropID.trimmed();
				// was ssn returned from dialog ?
.....
..... snip lot's of code .....
.....

/*
Program:	homestead.cpp
Description:	Homestead Application Program (HAP)
Author:		Jerry L Kreps
Date:		11/1/2005
*/
#include "homestead.h"
#include "wholenamedlg.h"
...
homestead::homestead(QWidget *parent) : QMainWindow(parent) {
	// homestead constructor method
	ui.setupUi(this);  // draw the gui interface
	this->Year65 = 1940;  // set birth year for 65 year olds
	this->dbYear = "2006";
...

	connect(ui.btnSearch, SIGNAL(clicked()), this, SLOT(searchAll()));
...
...
} // end of the homestead constructor

void homestead::searchAll() {
	// user enters value to search for in search text box
	// and clicks the radio button indicating its data type
        // then clicks the search button
	bool foundProp = false;
	bool foundPers = false;
	QString queryStr = "";
	QString seekWN = "'";  // set up for possible wholename search
	QString requestString;
	requestString = "Searching for: ";
	requestString.append(ui.leSearch->text()); // echo search request
	if (ui.rbWholeName->isChecked()) {
		QString partialName = ui.leSearch->text().trimmed();
		if (partialName.contains('%')){
			//select proprty_id,ssn,wholename,sssn,sname,city,address from persinfo_2006
			//WHERE wholename LIKE 'MILLER/E%'  ORDER BY wholename
			wholenamedlg dlg(this, partialName, this->dbYear, "F");
			if( dlg.exec() == QDialog::Accepted ){
				QString strSSN = dlg.resultSSN.trimmed();
				QString strPropID = dlg.resultPropID.trimmed();
				// was ssn returned from dialog ?
.....
..... snip lot's of code .....
.....

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Here is what the dialog looks like in action:
wholenamedlg_shown.jpg

[cioannou]

Don't touch those files and instead create another class. You can find the exact instructions here, but in short you need something like this:

#include <QDialog>
#include "ui_somedialog.h" // this file was made from somedialog.ui by uic
 
class SomeDialog : public QDialog
{
   Q_OBJECT
   public:
      SomeDialog( QWidget *parent = 0 );
 
   private slots:
      void searchAll();
etc. etc etc
}

#include <QDialog>
#include "ui_somedialog.h" // this file was made from somedialog.ui by uic

class SomeDialog : public QDialog
{
   Q_OBJECT
   public:
      SomeDialog( QWidget *parent = 0 );

   private slots:
      void searchAll();
etc. etc etc
}

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Ok , it's obvious that I am stupid and noob at the same time (in c++ & qt), so I can't be more embarassed.

here is my code:

#include <qapplication.h>
#include "ui_bullshit.h"
 
class bullshit : public QDialog
    {
        Q_OBJECT
 
    public:
        bullshit(QWidget *parent = 0);
 
    private:
        Ui::bullshit ui;
    };
 
 
bullshit::bullshit( QWidget *parent )
{
 
   ui.setupUi( this );
 
   // ...
}
 
 
int main(int argc, char **argv)
{
    QApplication    app(argc, argv);
 
    QDialog *window =  new QDialog;
    Ui::bullshit _ui;
    _ui.setupUi(window);
 
    window->show();
    return app.exec();
}

#include <qapplication.h>
#include "ui_bullshit.h"

class bullshit : public QDialog
    {
        Q_OBJECT

    public:
        bullshit(QWidget *parent = 0);

    private:
        Ui::bullshit ui;
    };


bullshit::bullshit( QWidget *parent )
{

   ui.setupUi( this );

   // ...
}


int main(int argc, char **argv)
{
    QApplication    app(argc, argv);

    QDialog *window =  new QDialog;
    Ui::bullshit _ui;
    _ui.setupUi(window);

    window->show();
    return app.exec();
}

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If i compile main.cpp it's ok , but linker gives me a nice error:

main.cpp undefined reference to `vtable for bullshit'

I should not paste the errors I get when I use a separate .h and .cpp for the class constructor and functions.

[jacek]

main.cpp undefined reference to `vtable for bullshit'

Add:

#include "main.moc"

#include "main.moc"

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at the end of main.cpp and run "qmake && make".

[cioannou]

Thanks a lot , it compiled && linked now, but still not working

#include <qapplication.h>
#include <qmessagebox.h>
 
#include "ui_bullshit.h"
 
class bullshit : public QDialog, private Ui::bullshit
    {
        Q_OBJECT
    public:
        bullshit(QWidget *parent = 0);
//    private:
//        Ui::bullshit ui;
 
    private slots:
        void msgbox();
        void on_helloButton_clicked();
    };
 
 
 
bullshit::bullshit( QWidget *parent ): QDialog(parent)
{
    setupUi(this);
 
    connect(helloButton,SIGNAL(clicked()),this,SLOT(msgbox()));
 
}
 
void bullshit::msgbox()
{
    QMessageBox::information(this, "Application name","The factory default will be used instead.");
}
 
 
 
void bullshit::on_helloButton_clicked()
{
    QMessageBox::information(this, "Application name","The factory default will be used instead.");
}

#include <qapplication.h>
#include <qmessagebox.h>

#include "ui_bullshit.h"

class bullshit : public QDialog, private Ui::bullshit
    {
        Q_OBJECT
    public:
        bullshit(QWidget *parent = 0);
//    private:
//        Ui::bullshit ui;

    private slots:
        void msgbox();
        void on_helloButton_clicked();
    };



bullshit::bullshit( QWidget *parent ): QDialog(parent)
{
    setupUi(this);

    connect(helloButton,SIGNAL(clicked()),this,SLOT(msgbox()));

}

void bullshit::msgbox()
{
    QMessageBox::information(this, "Application name","The factory default will be used instead.");
}



void bullshit::on_helloButton_clicked()
{
    QMessageBox::information(this, "Application name","The factory default will be used instead.");
}

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Can you please explain why we included the .moc file?

Txs

[jacek]

Thanks a lot , it compiled && linked now, but still not working

What do you mean by "not working"? How does your main() function look like?

Can you please explain why we included the .moc file?

Because you have placed definition of a class with Q_OBJECT macro in .cpp file. You wouldn't have to do it, if that class definition wes in a header.

[cioannou]

What do you mean by "not working"? How does your main() function look like?

int main(int argc, char **argv)
{
    QApplication    app(argc, argv);
 
    QDialog *window =  new QDialog;
    Ui::bullshit _ui;
    _ui.setupUi(window);
 
    window->show();
    QMessageBox::information(window, "startup msgbox",
    "The factory default will be used instead.");
    return app.exec();
}

int main(int argc, char **argv)
{
    QApplication    app(argc, argv);

    QDialog *window =  new QDialog;
    Ui::bullshit _ui;
    _ui.setupUi(window);

    window->show();
    QMessageBox::information(window, "startup msgbox",
    "The factory default will be used instead.");
    return app.exec();
}

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I mean that I press my helloButton but no QMessageBox appears.

Because you have placed definition of a class with Q_OBJECT macro in .cpp file. You wouldn't have to do it, if that class definition wes in a header.

Got it, thanks a lot.

[jacek]

I mean that I press my helloButton but no QMessageBox appears.

You don't instatiate your class anywhere.

Try:

int main( int argc, char **argv )
{
    QApplication app(argc, argv);
 
    bullshit *window =  new bullshit();
    window->show();
 
    QMessageBox::information( window, "startup msgbox", "The factory default will be used instead." );
    return app.exec();
}

int main( int argc, char **argv )
{
    QApplication app(argc, argv);

    bullshit *window =  new bullshit();
    window->show();

    QMessageBox::information( window, "startup msgbox", "The factory default will be used instead." );
    return app.exec();
}

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PS. Please, next time choose a different name for your class.

[cioannou]

You don't instatiate your class anywhere.

Try:

int main( int argc, char **argv )
{
    QApplication app(argc, argv);
 
    mydialogclass *window =  new mydialogclass();
    window->show();
 
    QMessageBox::information( window, "startup msgbox", "The factory default will be used instead." );
    return app.exec();
}

int main( int argc, char **argv )
{
    QApplication app(argc, argv);

    mydialogclass *window =  new mydialogclass();
    window->show();

    QMessageBox::information( window, "startup msgbox", "The factory default will be used instead." );
    return app.exec();
}

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PS. Please, next time choose a different name for your class.

Ooops. This was really noob.

Sorry for the class name, it just came out from my dissapointment.

Already 'renamed' it.

[cioannou]

I am sorry but it still doesn't work.

If I connect the button to an existing slot e.g. accept() then the button works.

#include <qapplication.h>
#include <qdialog.h>
#include <qmessagebox.h>
#include "ui_MyDialog.h"
 
class MyDialog : public QDialog
{
    public:
        MyDialog(QWidget *parent = 0);
    private:
     Ui::MyDialog ui;
    private slots:
        void msgbox();
};
 
MyDialog::MyDialog( QWidget *parent )
{
    ui.setupUi(this);
 
    connect(ui.helloButton,SIGNAL(clicked()),this,SLOT(msgbox()));
    connect(ui.pressMe,SIGNAL(clicked()),this,SLOT(accept()));
}
 
void MyDialog::msgbox()
{
     QMessageBox::information(0, "test","message");
}
 
int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    MyDialog *window=new MyDialog;
 
    window->show();
    return app.exec();
}

#include <qapplication.h>
#include <qdialog.h>
#include <qmessagebox.h>
#include "ui_MyDialog.h"

class MyDialog : public QDialog
{
    public:
        MyDialog(QWidget *parent = 0);
    private:
     Ui::MyDialog ui;
    private slots:
        void msgbox();
};

MyDialog::MyDialog( QWidget *parent )
{
    ui.setupUi(this);

    connect(ui.helloButton,SIGNAL(clicked()),this,SLOT(msgbox()));
    connect(ui.pressMe,SIGNAL(clicked()),this,SLOT(accept()));
}

void MyDialog::msgbox()
{
     QMessageBox::information(0, "test","message");
}

int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    MyDialog *window=new MyDialog;

    window->show();
    return app.exec();
}

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[jacek]

I am sorry but it still doesn't work.

Because there is no Q_OBJECT macro, you need it if you define new signals or slots in your class.

class MyDialog : public QDialog
{
    Q_OBJECT
    public:
       ...
};

class MyDialog : public QDialog
{
    Q_OBJECT
    public:
       ...
};

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[cioannou]

OK guys , I got it!!!!

here it is:

mydialog.h

#include <qapplication.h>
#include <qdialog.h>
#include <qmessagebox.h>
#include "ui_MyDialog.h"  //This is the header generated by uic Mydialog.ui > ui_MyDialog.h
 
class MyDialog : public QDialog
{
    Q_OBJECT
 
    public:
        MyDialog(QWidget *parent = 0);
    private:
     Ui::MyDialog ui;
    private slots:
        void msgbox();
};

#include <qapplication.h>
#include <qdialog.h>
#include <qmessagebox.h>
#include "ui_MyDialog.h"  //This is the header generated by uic Mydialog.ui > ui_MyDialog.h

class MyDialog : public QDialog
{
    Q_OBJECT

    public:
        MyDialog(QWidget *parent = 0);
    private:
     Ui::MyDialog ui;
    private slots:
        void msgbox();
};

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mydialog.cpp

#include "mydialog.h"
 
MyDialog::MyDialog( QWidget *parent )
{
    ui.setupUi(this);
 
    connect(ui.helloButton,SIGNAL(clicked()),this,SLOT(msgbox()));
    connect(ui.pressMe,SIGNAL(clicked()),this,SLOT(accept()));
}
 
void MyDialog::msgbox()
{
    QMessageBox::information(0, "test","message");
}

#include "mydialog.h"

MyDialog::MyDialog( QWidget *parent )
{
    ui.setupUi(this);

    connect(ui.helloButton,SIGNAL(clicked()),this,SLOT(msgbox()));
    connect(ui.pressMe,SIGNAL(clicked()),this,SLOT(accept()));
}

void MyDialog::msgbox()
{
    QMessageBox::information(0, "test","message");
}

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main.cpp

#include <qapplication.h>
#include <qdialog.h>
#include <qmessagebox.h>
#include "mydialog.h"
 
int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    MyDialog *window=new MyDialog;
 
    window->show();
    return app.exec();
}

#include <qapplication.h>
#include <qdialog.h>
#include <qmessagebox.h>
#include "mydialog.h"

int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    MyDialog *window=new MyDialog;

    window->show();
    return app.exec();
}

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I still get an error concerning 'undefined reference to vtable for MyDialog' if I build inside Code::Blocks.

If I use:

qmake
mingw32-make

It works (finally!!!)

[jacek]

I still get an error concerning 'undefined reference to vtable for MyDialog' if I build inside Code::Blocks.

If I use:

qmake
mingw32-make

It works (finally!!!)

Every time you add or remove Q_OBJECT macro, you have to rerun qmake.

[yop]

I still get an error concerning 'undefined reference to vtable for MyDialog' if I build inside Code::Blocks.

Create a custom tool that runs qmake in your project and on the project options select "Using a custom makefile". Then you only have to run your tool every time you add a new file to the project and then just build with the outputed makefile. It's the same as typing it but you get it with a couple of clicks

[cioannou]

Thanks for the info, I will try it.

I have now added a listbox to my dialog.

Can you point me to some docs about how to get a reference to that listbox and e.g. add some items?

Txs

[GreyGeek]

That's exactly what I am trying to avoid.
If I change the app.h that is generated by the designer and afterwards add some new widgets to my dialog, all my private slots will be lost.

Am I missing something?

Yes. I am refering to app.h ... NOT app.ui or the ui_app.h file which the MOC creates.

The app.h file ISN'T generated by the designer. It's created by you!

In QT4 all the designer program does is create your ui interfaces. Any signal/slot connections you create with it apply only to the form itself or those objects that you placed on the form as you design your gui. You cannot use the designer to connect to a signal or slot which is not among those the designer adds itself to your ui. Ergo, you must create your own classes and add your external signals and slots to compliment the ui you design.

When I first switched to QT4 and left the QT3 Designer behind I was, at first, bewildered because I had learned how to make connections between objects, in the ui or out, strictly with the designer. It actually crippled me as far as learning how to OOP program using C++. Jacek was right. I am glad I hadn't burned the QT3 Designer habits as deeply into my 65 year old brain as long use of it would have done.