[Beginner Question] Cannot get this Code to run

devwatch

Hello Community, i play a little bit with signals/slots (hte manual way) but my code does not work.

@
#include <QtGui>
#include <QMessageBox>

class Demo : public QObject
{
Q_OBJECT

public slots:
void showMessage();

public:

Demo(){}

};

void Demo::showMessage()
{
QMessageBox::information(0,"Message","Hello World",QMessageBox::Ok);

}

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

//Create a new QPushButton
QPushButton * button = new QPushButton("Hello Wolrd!");
button->show();

//Construct my Class
Demo *dapp = new Demo();

//Here i try to connect that on pressing the Button the Demo->showMessage Member will be displayed
QObject::connect(&button,SIGNAL(clicked()),&app,SLOT(showMessage()));

return app.exec();
}
@

What did i wrong in the connect Member?

Thanks for Help!

goetz

You must connect to the Demo object, not the QApplication object:

@
QObject::connect(&button,SIGNAL(clicked()),dapp,SLOT(showMessage()));
@

You should have got a warning message that the connect failed on application startup.

devwatch

Danke Volker!

goetz

No problem - you're welcome.

tobias.hunger

The "&button" should really just be "button". button already is a pointer, no need to turn it into a pointer to a pointer...

broadpeak

Sorry, but you are a little bit inconsecutive (see the "star" place):

char* argv[]
Demo *dapp
QPushButton * button

This can confuse other developers.
Be consecutive!

When you declare (or define) a pointer, bind the "star" to the type, and when you dereference a pointer, bind the "star" to the variable name.

devwatch

Yea, thank you i will declare it better in my next little failure programms :)