signals and slots problem

[sonuani]

hi,
If my lineedit control changes then a message has to be displayed.
I have dont like this.

public slots:
OnChangelineedit();
 
connect(lineedit1, SIGNAL(cursorPositionChanged(0,1)),
		this, SLOT(OnChangelineedit()));

public slots:
OnChangelineedit();

connect(lineedit1, SIGNAL(cursorPositionChanged(0,1)),
		this, SLOT(OnChangelineedit()));

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But i am getting error"

Object::connect: No such signal QLineEdit::cursorPositionChanged(0,1)
Object::connect: (sender name: 'lineedit1)
Object::connect: (receiver name: 'dialog')".

What is wrong with my code.

[jpn]

I recommend reading about signals and slots. You can't put parameter names or values but only parameter types in connect statement.

[topher]

How about this...

connect(lineedit1, SIGNAL(cursorPositionChanged(int, int)), this, SLOT(OnChangelineedit()));

connect(lineedit1, SIGNAL(cursorPositionChanged(int, int)), this, SLOT(OnChangelineedit()));

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[cyan21]

Hello,

I'm using Eclipse and QT4 and I get exactly the same problem but the previous post doesn't really help very much.

#ifndef TEST_QT_H
#define TEST_QT_H
 
#include <QtGui/QWidget>
#include "ui_test_qt.h"
 
class test_qt : public QWidget
{
    Q_OBJECT
 
public:
    test_qt(QWidget *parent = 0);
    ~test_qt();
 
private:
    Ui::test_qtClass ui;
 
public slots:
	void test();
};
 
#endif // TEST_QT_H

#ifndef TEST_QT_H
#define TEST_QT_H

#include <QtGui/QWidget>
#include "ui_test_qt.h"

class test_qt : public QWidget
{
    Q_OBJECT

public:
    test_qt(QWidget *parent = 0);
    ~test_qt();

private:
    Ui::test_qtClass ui;
    
public slots:
	void test();
};

#endif // TEST_QT_H

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#include "test_qt.h"
 
test_qt::test_qt(QWidget *parent)
    : QWidget(parent)
{
	ui.setupUi(this);
	connect(ui.pButton, SIGNAL(clicked()), ui.label, SLOT(test()));
}
 
test_qt::~test_qt()
{
 
}
 
void test_qt::test()
{
	ui.label->setText("GO");
}

#include "test_qt.h"

test_qt::test_qt(QWidget *parent)
    : QWidget(parent)
{
	ui.setupUi(this);
	connect(ui.pButton, SIGNAL(clicked()), ui.label, SLOT(test()));
}

test_qt::~test_qt()
{

}

void test_qt::test()
{
	ui.label->setText("GO");
}

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I get this error:

Object::connect: No such slot QLabel::test()
Object::connect:  (sender name:   'pButton')
Object::connect:  (receiver name: 'label')

Object::connect: No such slot QLabel::test()
Object::connect:  (sender name:   'pButton')
Object::connect:  (receiver name: 'label')

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can somebody help me on this ?
thanks

[jpn]

You are passing an incorrect receiver to the connect statement. QLabel does not have such slot as "test()". The test_qt class written by you does. So you should not pass "ui.label" but something else to the connect statement.

[windsword]

Hell I have a similar problem, the error message I get is:
Object::connect: No such slot QWidget::adminstart()

If I add Q_OBJECT to my class, I get the following error msg when I type "make"
ndefined symbols:
"vtable for harpWin", referenced from:
__ZTV7harpWin$non_lazy_ptr in harpwin.o
ld: symbol(s) not found
collect2: ld returned 1 exit status

Here is my code (all in one file ):

class harpWin : public QWidget
{
    Q_OBJECT
 
public:
      harpWin(QWidget *parent = 0);
      ~harpWin();
 
      QGraphicsView *graphicsView;
      QPushButton *adminButton;
      QPushButton *measureButton;
      QPushButton *viewButton;
      QPushButton *quitButton;
      QVBoxLayout *vboxLayout;
      QHBoxLayout *hboxLayout;
 
public slots:
      void adminstart();
};
 
harpWin::harpWin( QWidget *parent)
    : QWidget(parent)
{
    setWindowTitle("Harp Win0");
    vboxLayout = new QVBoxLayout();
    hboxLayout = new QHBoxLayout();
 
    graphicsView = new QGraphicsView(this);
    adminButton   = new QPushButton("Admin", this);
    adminButton->setDefault(true);
    measureButton = new QPushButton("Measure", this);
    viewButton    = new QPushButton("View", this);
    quitButton    = new QPushButton("&Quit",this);
 
    vboxLayout->addWidget(adminButton);//,  1, Qt::AlignRight);
    vboxLayout->addWidget(measureButton);
    vboxLayout->addWidget(viewButton);
    vboxLayout->addWidget(quitButton);
 
    hboxLayout->addWidget(graphicsView, 1, Qt::AlignLeft);
    hboxLayout->addLayout(vboxLayout);
    setLayout(hboxLayout);
 
    QObject::connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit()));
    connect(adminButton, SIGNAL(clicked()), this, SLOT( adminstart() ));
    QObject::connect(viewButton, SIGNAL(clicked()), qApp, SLOT(quit()));
    QObject::connect(measureButton, SIGNAL(clicked()), qApp, SLOT(quit()));
}
 
harpWin::~harpWin()
{
 
}
 
void harpWin::adminstart()
{       
        QString str = "\n clicked button\n";
        qDebug() << str;
}
 
 
int main(int argc, char *argv[])
{   
    QApplication app(argc, argv);
 
    harpWin introWindow;
 
    //introWindow.setWindowTitle("Absolute");
    introWindow.show();
 
    return app.exec();
}

class harpWin : public QWidget
{
    Q_OBJECT

public:
      harpWin(QWidget *parent = 0);
      ~harpWin();

      QGraphicsView *graphicsView;
      QPushButton *adminButton;
      QPushButton *measureButton;
      QPushButton *viewButton;
      QPushButton *quitButton;
      QVBoxLayout *vboxLayout;
      QHBoxLayout *hboxLayout;

public slots:
      void adminstart();
};

harpWin::harpWin( QWidget *parent)
    : QWidget(parent)
{
    setWindowTitle("Harp Win0");
    vboxLayout = new QVBoxLayout();
    hboxLayout = new QHBoxLayout();

    graphicsView = new QGraphicsView(this);
    adminButton   = new QPushButton("Admin", this);
    adminButton->setDefault(true);
    measureButton = new QPushButton("Measure", this);
    viewButton    = new QPushButton("View", this);
    quitButton    = new QPushButton("&Quit",this);

    vboxLayout->addWidget(adminButton);//,  1, Qt::AlignRight);
    vboxLayout->addWidget(measureButton);
    vboxLayout->addWidget(viewButton);
    vboxLayout->addWidget(quitButton);
    
    hboxLayout->addWidget(graphicsView, 1, Qt::AlignLeft);
    hboxLayout->addLayout(vboxLayout);
    setLayout(hboxLayout);
    
    QObject::connect(quitButton, SIGNAL(clicked()), qApp, SLOT(quit()));
    connect(adminButton, SIGNAL(clicked()), this, SLOT( adminstart() ));
    QObject::connect(viewButton, SIGNAL(clicked()), qApp, SLOT(quit()));
    QObject::connect(measureButton, SIGNAL(clicked()), qApp, SLOT(quit()));
}

harpWin::~harpWin()
{

}

void harpWin::adminstart()
{       
        QString str = "\n clicked button\n";
        qDebug() << str;
}


int main(int argc, char *argv[])
{   
    QApplication app(argc, argv);
    
    harpWin introWindow;
    
    //introWindow.setWindowTitle("Absolute");
    introWindow.show();
    
    return app.exec();
}

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[jacek]

If I add Q_OBJECT to my class, I get the following error msg when I type "make"

Do you use qmake? If yes, then you have to re-run it after you add Q_OBJECT macro.