Need help with a basic calculator

[Morea]

I have attached the code, the problem is: it doesn't show anything. I can't figure out why. I think I've done it right, but obviously I haven't.
Can you see why I don't get any out put?

[zlatko]

Yes you forgot set main widget for your app..look in next code

#include <QApplication>
 
#include "mainwindow.h"
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow *MainForm = new MainWindow;
    app.setMainWidget(MainForm);
    MainForm->show();
    return app.exec();
 
}

#include <QApplication>

#include "mainwindow.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow *MainForm = new MainWindow;
    app.setMainWidget(MainForm);
    MainForm->show();
    return app.exec();
    
}

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[jpn]

I have attached the code, the problem is: it doesn't show anything. I can't figure out why. I think I've done it right, but obviously I haven't.
Can you see why I don't get any out put?

You can't add parameter values to signal-slot connections.
In the constructor of MainWindow:

change:

connect(ui.siffra9,SIGNAL(clicked()),&C,SLOT(addToCurrentNumber(9)));
[...]
connect(ui.siffra0,SIGNAL(clicked()),&C,SLOT(addToCurrentNumber(0)));

connect(ui.siffra9,SIGNAL(clicked()),&C,SLOT(addToCurrentNumber(9)));
[...]
connect(ui.siffra0,SIGNAL(clicked()),&C,SLOT(addToCurrentNumber(0)));

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to:

#include <QSignalMapper>
 
QSignalMapper* mapper = new QSignalMapper(this);
 
connect(ui.siffra9, SIGNAL(clicked()), mapper, SLOT(map()));
mapper->setMapping(ui.siffra9, 9);
[...]
connect(ui.siffra0, SIGNAL(clicked()), mapper, SLOT(map()));	
mapper->setMapping(ui.siffra0, 0);
 
connect(mapper, SIGNAL(mapped(int)), &C, SLOT(addToCurrentNumber(int)));

#include <QSignalMapper>

QSignalMapper* mapper = new QSignalMapper(this);

connect(ui.siffra9, SIGNAL(clicked()), mapper, SLOT(map()));
mapper->setMapping(ui.siffra9, 9);
[...]
connect(ui.siffra0, SIGNAL(clicked()), mapper, SLOT(map()));	
mapper->setMapping(ui.siffra0, 0);
	
connect(mapper, SIGNAL(mapped(int)), &C, SLOT(addToCurrentNumber(int)));

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[Morea]

Yes you forgot set main widget for your app..look in next code

#include <QApplication>
 
#include "mainwindow.h"
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow *MainForm = new MainWindow;
    app.setMainWidget(MainForm);
    MainForm->show();
    return app.exec();
 
}

#include <QApplication>

#include "mainwindow.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow *MainForm = new MainWindow;
    app.setMainWidget(MainForm);
    MainForm->show();
    return app.exec();
    
}

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Strange, I've managed without that before.

[Morea]

You can't add parameter values to signal-slot connections.
In the constructor of MainWindow:

change:

connect(ui.siffra9,SIGNAL(clicked()),&C,SLOT(addToCurrentNumber(9)));
[...]
connect(ui.siffra0,SIGNAL(clicked()),&C,SLOT(addToCurrentNumber(0)));

connect(ui.siffra9,SIGNAL(clicked()),&C,SLOT(addToCurrentNumber(9)));
[...]
connect(ui.siffra0,SIGNAL(clicked()),&C,SLOT(addToCurrentNumber(0)));

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to:

#include <QSignalMapper>
 
QSignalMapper* mapper = new QSignalMapper(this);
 
connect(ui.siffra9, SIGNAL(clicked()), mapper, SLOT(map()));
mapper->setMapping(ui.siffra9, 9);
[...]
connect(ui.siffra0, SIGNAL(clicked()), mapper, SLOT(map()));	
mapper->setMapping(ui.siffra0, 0);
 
connect(mapper, SIGNAL(mapped(int)), &C, SLOT(addToCurrentNumber(int)));

#include <QSignalMapper>

QSignalMapper* mapper = new QSignalMapper(this);

connect(ui.siffra9, SIGNAL(clicked()), mapper, SLOT(map()));
mapper->setMapping(ui.siffra9, 9);
[...]
connect(ui.siffra0, SIGNAL(clicked()), mapper, SLOT(map()));	
mapper->setMapping(ui.siffra0, 0);
	
connect(mapper, SIGNAL(mapped(int)), &C, SLOT(addToCurrentNumber(int)));

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I will try that, thank you.
Are there any other way of getting the same functionality? I mean, a different design, or you will most likely need to use the mapper unless you wish to create 10 different slots, one for each digit?

[jpn]

I will try that, thank you.
Are there any other way of getting the same functionality? I mean, a different design, or you will most likely need to use the mapper unless you wish to create 10 different slots, one for each digit?

The signal mapper is intended for situations like yours.
Yes, one approach could be to create a bunch of slots, a different slot for each digit.. Not very handy, right

[jpn]

Yes you forgot set main widget for your app..look in next code

Isn't application's main widget obsolete in Qt 4..

[wysota]

One could use a QButtonGroup instead of a signal mapper too. It would be more natural than using QSignalMapper.