Writing custom slot method based on QT example 1&2

[kaydknight]

Hi, I have a question. I've been studying through tutorials under Qt. What I notice is that when you want to implement your custom slots, you have to create a custom widget and implement the slot methods inside the class.

But what if I want to create my own slots without having a need to create a class? Based on the simple example below, without creating a custom widget class, I want to implement a custom slot method "customMethod".

#include <QApplication>
#include <QPushButton>
#include <QObject>
 
// I want to implement a method called customMethod here
// tried void QApplication::customMethod() but didn't work
void customMethod()
{
	//I want to do something here.
}
 
int main(int argc, char* argv[])
{
	QApplication app(argc,argv);
	QPushButton button("Quit");
	QObject::connect(button,SIGNAL(clicked()), &app,SLOT(customMethod()));
	button.show();
 
	return app.exec();
}

#include <QApplication>
#include <QPushButton>
#include <QObject>

// I want to implement a method called customMethod here
// tried void QApplication::customMethod() but didn't work
void customMethod()
{
	//I want to do something here.
}

int main(int argc, char* argv[])
{
	QApplication app(argc,argv);
	QPushButton button("Quit");
	QObject::connect(button,SIGNAL(clicked()), &app,SLOT(customMethod()));
	button.show();
	
	return app.exec();
}

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I'm guessing that I can't do the above, and I have to create custom widget class or something. What I was thinking, for example, is there a way, based on above coding to add my own about messagebox, using QMessageBox::information(//parameters).

Thanks in advance!

[e8johan]

There is no need to create a custom widget, but you will have to put your slot in a class inheriting QObject and including the Q_OBJECT macro. This is because slots are based on the meta data system, and only QObjects has meta objects.

Since QWidget inherits QObject it has a is-a relations. I.e. QWidget is-a QObject thus has a meta object.