Question

I have a Qt Form that contains 2 combo box messages. The second combobox message depends on the first combo box message. I mean that the dates from the second combobox message depends on the element that I select in the first combobox.
In this moment I have different dates in the first combobox. But the second combobox is not working. I need to creare a connect method or what?
Thx! APpreciate!
Could someone give me a short example?

Answer 1

It’s fairly simple. A combobox emits the currentIndexChanged signal that also tells you the new index. Write a method that accepts an integer and changes the second combobox according to the integer (which is the index of the selection in combobox 1).

Here are some code sniplets from a working example.

Method declaration in your window/whatever class header:

public slots:
    void setI1(int index);

Filling combobox 1, connecting the signal, e.g. in the constructor:

i1Box->addItem("Neutral", 0);
i1Box->addItem("2,856 K (Illuminant A, light bulb)",    2856);
// ...

connect(i1Box, SIGNAL(currentIndexChanged(int)),
        this, SLOT(setI1(int)));

Implementation of the method:

void ViewerWindow::setI1(int index) {
    // either use index directly, or, as in this case we have items holding an int:
    int i1 = i1Box->itemData(index).value<int>();
    // use the value to change second combobox here
}

If it does not work as expected, it is always helpful to print some debug output inside the method that should be called to see where it goes wrong in the chain.

Reference: http://doc.qt.nokia.com/latest/signalsandslots.html