Required a pointer "this" to QWidget inside a component class.

[ZikO]

Hello,

I have recently found a problem when I wanted to use a Qt dialog window to show information or ask for a file path. The problem is that I need to do it inside a constructor of another class. If I had an arbitrary code below, what would I need put in the line 43 (inside a constructor of class A) to open QMessageBox that requires a pointer "this" to my window class? If I inherited from MyWindow, would something like &(static_cast<MyWindow&>(*this)) work?

Thanks

#include <QApplication>
#include <QMessageBox>
#include <QWidget>
 
////////////////////////////////////////
class MyWindow : public QWidget {
	Q_OBJECT
public:
	MyWindow(QWidget* parent = 0);
 
public slots:
signals:	
};
 
class A {
	int a;
	double b;
public:
	A(int _a = 0, double _b = 0.0);
};
////////////////////////////////////////
 
///// ===== main function ====
int main(int argc, char* argv[]) {
	QApplication app(argc,argv);
 
	return app.exec();
}
///// ===== end of main ======
 
///// MyWindow //////////////////////////
MyWindow::MyWindow(QWidget* parent)
		: QWidget(parent) {
		// Create Layout, actions, menus, etc.
		A object_A(10,20.5);		
}
///// End of MyWindow ///////////////////
 
///// A /////////////////////////////////
A::A(int _a, double _b) : a(_a), b(_b) {
	// Some problems here and information need to be shown:
	QMessageBox::information(
			this,
			tr("Title"),
			tr("Information to be shown"));
}
///// End of A //////////////////////////

#include <QApplication>
#include <QMessageBox>
#include <QWidget>

////////////////////////////////////////
class MyWindow : public QWidget {
	Q_OBJECT
public:
	MyWindow(QWidget* parent = 0);

public slots:
signals:	
};

class A {
	int a;
	double b;
public:
	A(int _a = 0, double _b = 0.0);
};
////////////////////////////////////////

///// ===== main function ====
int main(int argc, char* argv[]) {
	QApplication app(argc,argv);
	
	return app.exec();
}
///// ===== end of main ======

///// MyWindow //////////////////////////
MyWindow::MyWindow(QWidget* parent)
		: QWidget(parent) {
		// Create Layout, actions, menus, etc.
		A object_A(10,20.5);		
}
///// End of MyWindow ///////////////////

///// A /////////////////////////////////
A::A(int _a, double _b) : a(_a), b(_b) {
	// Some problems here and information need to be shown:
	QMessageBox::information(
			this,
			tr("Title"),
			tr("Information to be shown"));
}
///// End of A //////////////////////////

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PS. I did not really run this code. It is only to show the problem.

[amleto]

why not just use NULL?

Otherwise change A like

class A {
int a;
double b;
public:
A(int _a = 0, double _b = 0.0, QWidget* parentForMsgBox = 0);
};
 
...

class A {
int a;
double b;
public:
A(int _a = 0, double _b = 0.0, QWidget* parentForMsgBox = 0);
};

...

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[ZikO]

Hello,

OK. Thanks for this advice. I usually do so providing a full code. I did think my code was too long and it would take the whole page. Also, the code was separated into several headers / source files due to a few classes / structures I have implemented. I just assumed the problem would be to trivial but I will follow this rule next time.

As to the problem, it works now. I came here because I am still a newbie programmer and I did expect the problem would be solved in a very easy way. I really should have found it by myself :/ somehow still not experienced enough to realise that extra argument would solve the problem.

Thank you.