why append Slot doesn't work?

Question

Hi all, I have got a problem when I try to make following simple connections

QSpinBox *spinBox = new QSpinBox;
QSlider *slider = new QSlider(Qt::Horizontal);
QTextEdit *text = new QTextEdit("Hello QT!");

QObject::connect(spinBox, SIGNAL(valueChanged(int)),slider, SLOT(setValue(int)));
QObject::connect(slider, SIGNAL(valueChanged(int)),spinBox, SLOT(setValue(int)));
QObject::connect(slider,SIGNAL(valueChanged(int)),text, SLOT(append("slider changed!")));
QObject::connect(spinBox,SIGNAL(valueChanged(int)),text, SLOT(append("spinbox changed!")));
QObject::connect(text,SIGNAL(textChanged()),spinBox,SLOT(clear()));

It can be successfully compiled and excuted.But the two append slots seem not work.I've checked the help manual about QTextEdit and there's a public slot append there.Have I missed something?Help would be appreciated!

Answer 1

Unfortunately, you cannot pass custom values to your slots via QObject::connect (only type information for the arguments is allowed/interpreted correctly). Instead, create your own slot, something like

void MyWidget::mySliderChangedSlot(int newValue)
{
  text->append("slider changed!");
}

and use

QObject::connect(slider, SIGNAL(valueChanged(int)), pMyWidget, SLOT(mySliderChangedSlot(int)));

to achieve your desired behaviour.

I hope that helps.

Answer 2

What exactly are you trying to do? That has now way of working because you connect a signal which has an int param to a slot with a string parameter for one, the other thing is that the signal slots where not meant for this kind of usage you just say wich function are conected and they pass parameters betwen them you dont pass the values yourself, you are not using them correctly read the documentation at http://doc.trolltech.com/4.6/signalsandslots.html for correct usage examples.