dynamcly allocated buttons

[MarkoSan]

Hi to all!

I've dynamically created buttons (the number of them is NOT known at compile time, but at runtime). It works ok, buttons are shown as I wanted. But now, I need to connect every button's signal clicked() to some slot function. How do I provide slot functions at runtime??

[MarkoSan]

It look like I did it on my own. But it does not work. Is it allowed to setup slot from one object and then call slot from different object?

I got to gdb and i get following message:

warning: Object::connect: No such slot COperationWIndow::m_pMerchandizeBrowser->fillMerchandize(iIndex)

warning: Object::connect: No such slot COperationWIndow::m_pMerchandizeBrowser->fillMerchandize(iIndex)

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Why this does not work?

[wysota]

How do I provide slot functions at runtime??

I don't think you can add methods to classes at runtime in C++

Is it allowed to setup slot from one object and then call slot from different object?

If you think about something like this:

connect(object1, SIGNAL(sig()), object2, SLOT(sl())); // "this" is neither object1 nor object2

connect(object1, SIGNAL(sig()), object2, SLOT(sl())); // "this" is neither object1 nor object2

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then yes.

[MarkoSan]

Well, if I got it right, then:

m_MerchandizeSelectorButtons.at(iIndex)->connect(m_pButtonMerchandizeConfirmer,
                                                         SIGNAL(clicked()),
                                                         this. SLOT(m_pMerchandizeBrowser->fillMerchandize(iIndex)));

m_MerchandizeSelectorButtons.at(iIndex)->connect(m_pButtonMerchandizeConfirmer,
                                                         SIGNAL(clicked()),
                                                         this. SLOT(m_pMerchandizeBrowser->fillMerchandize(iIndex)));

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then second "this" is the name of "target" object?

[jpn]

You can't put a statement into SLOT() macro like that. Take a look at QButtonGroup or QSignalMapper.

[MarkoSan]

QSIgnalMapper? I hate it, I've never understood it, I've read the docs about QSignalMapper but it is my humble opinion these docs are not written at the best ...

[jpn]

QSIgnalMapper? I hate it, I've never understood it, I've read the docs about QSignalMapper but it is my humble opinion these docs are not written at the best ...

To be direct and honest, you should start with reading the article about signals and slots. It's the very basic principle of signals and slots that the SLOT() macro takes a slot name plus optional parameter types, without parameter names, and nothing more. Once you understand how signals and slots work, it should be straightforward to understand QSignalMapper docs. Besides, QButtonGroup should be even easier to use...

[MarkoSan]

Ok, but I simply must overcome this QSignalMapper since it is very useful. I understand signal/slots feature, but this QSignalMapper is giving me headache. Now let me dig into it ...

[MarkoSan]

Does every button in a QList <QPushButton*> need its own QSIgnalMapper?

[jacek]

Does every button in a QList <QPushButton*> need its own QSIgnalMapper?

No, you need only one signal mapper for the whole list.

In Qt docs you can find such example:

...
for (int i = 0; i < texts.size(); ++i) {
    QPushButton *button = new QPushButton(texts[i]);
    connect(button, SIGNAL(clicked()), signalMapper, SLOT(map()));
    signalMapper->setMapping(button, texts[i]);
    ...
}
 
connect(signalMapper, SIGNAL(mapped(const QString &)),
        this, SIGNAL(clicked(const QString &)));
...

...
for (int i = 0; i < texts.size(); ++i) {
    QPushButton *button = new QPushButton(texts[i]);
    connect(button, SIGNAL(clicked()), signalMapper, SLOT(map()));
    signalMapper->setMapping(button, texts[i]);
    ...
}

connect(signalMapper, SIGNAL(mapped(const QString &)),
        this, SIGNAL(clicked(const QString &)));
...

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The setMapping() line tells the signal mapper that whenever the particular button invokes map(), the signal mapper should emit mapped(const QString &) signal with given parameter. So in this case you can replace all clicked() signals coming from different buttons with a single mapped( const QString & ) signal that comes from the signal mapper (of course parameter value depends on which button sent the original signal).

You can have a mapped() signal also with integer, QObject * or QWidget * parameter --- you just have to use the other setMapping() method variants instead.

In your case you can use QButtonGroup as jpn has suggested. Basically it's like a QSignalMapper but crafted especially for buttons.

[MarkoSan]

I would stick to QSignalMapper because I simply must overcome this topic. So, let me dig into it and try to reprogramm the example...

Well, I've done this:

m_MerchandizeSelectorButtons.at(iIndex)->connect(m_MerchandizeSelectorButtons.at(iIndex),
                                                         SIGNAL(clicked()),
                                                         m_pMerchandizeSelectorButtonSignalMapper,
                                                         SLOT(map()));

m_MerchandizeSelectorButtons.at(iIndex)->connect(m_MerchandizeSelectorButtons.at(iIndex),
                                                         SIGNAL(clicked()),
                                                         m_pMerchandizeSelectorButtonSignalMapper,
                                                         SLOT(map()));

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What should I now put into map() slot? Call to other's object slot?