My first program which realy do something!!

[Kyon]

Well, I'm not entirely sure, but from what I heard, QApplication's destructor provides that functionality. It's true C++ doesn't support this by itself, but the class can be defined to work just so.

About the dynamic allocation, the syntax implies that the following can be done (or in a similar way, not entirely sure whether it's this EXACT code).

#include <QtGui/qapplication.h>
#include <QtGui/qlabel.h>

int main(int argc, char* argv[])
{
   QApplication app(argc, argv);
   QLabel label("Hello Qt!", 0);
   app.setActiveWindow(&label);
   label.show();
   return app.exec();
}

EDIT: Made a slight mistake, thanks bbgst for pointing that out. ;)

[bbgst]

Why bother if QApplication reference counts or not? Just use a local variable as the above. Except for:

app.setActiveWindow(*label);

which should be

app.setActiveWindow(&label);

[codekiddy]

@bbgst
and what if that object is so big that system can't alocate enough memory for it on the stack?

[LB]

Obviously you are incredibly smart and know when you need to instantiate a big object on the heap instead of the stack. If you're not, then you can just do trial and error once ;p

[helios]

Has anyone ever even encountered such a type? The really large objects store just a minute fraction of their data in members. Most of it goes in the heap anyway, regardless of how the object was allocated.

[Catfish]

If you're not using new for polymorphism, then don't use it at all. Smells like Java.

[helios]

Smells like Java.

*Sigh*
Of all the stupid arguments I've heard...

[chrisname]

helios wrote:

Has anyone ever even encountered such a type?

Has anyone really been far even as decided to use even go want to do such a type?

@Catfish,
Even if that was a Java idiom, what would be wrong with that? I don't particularly like Java (but I <3 C#) but that doesn't mean it doesn't have any useful additions that can be brought into C++ (or at least, emulated in C++).

Doing something like #define extends : would be a bit different though.

[hamsterman]

I haven't used Qt for a while, so I'm not sure, but I think that I had got a segfault due to declaring my locals in a wrong order. Maybe a child widget's destructor does some cleanup with its parent, so if that gets destroyed first, it's a problem. I don't have Qt or even a C++ compiler installed currently to test it..

[andywestken]

Do you need the setActiveWindow() call?

Nokia's site gives the following example:
http://doc.qt.nokia.com/stable/gettingstartedqt.html

         #include <QApplication>
         #include <QTextEdit>
 
         int main(int argv, char **args)
         {
             QApplication app(argv, args);

             QTextEdit textEdit;
             textEdit.show();
 
             return app.exec();
         }

[codekiddy]

setActiveWindow()

not shore, still learning Qt, but AFAIK setActiveWindow(textEdit) metod tels the application explicitly that this widget is main widget, means it has no parents.
all other widgets are textEdit's children.

[Catfish]

helios wrote:

Of all the stupid arguments I've heard...

Sigh... it wasn't an argument, lighten up.