mapping data to a QComboBox

mzimmers

Hi all -

I'm playing with model/view stuff, and learning (slowly) as I go. I'm trying to map a data column from a QStandardItemModel to a QComboBox.

model.cpp

...
    qs = d.ledPattern;
    rc = m_model->setData(m_model->index(row, MODEL_COL_LED_PATTERN), qs);

and widget.cpp

const string ledPatternText[LEDC_NBR_PATTERNS] =
{
    "SOLID_OFF",
    "SOLID_ON",
    "FLASH_SLOW",
    "FLASH_RAPID"
};
...
    for (int i = 0; i < LEDC_NBR_PATTERNS; ++i)
    {
        qs = QString::fromStdString(ledPatternText[i]);
        ui->comboBoxLedPattern->addItem(qs);
    }
    mapper->addMapping(ui->comboBoxLedPattern, MODEL_COL_LED_PATTERN);

The combo box doesn't seem mapped to the data. It always displays "SOLID_OFF." Can someone see what I'm doing wrong here?

SGaist

Hi,

Did you already check the Combo Box Widget Mapper Example ?

mzimmers

I did now.

So...model.cpp:

    QString qs;
    QStringList qsl;
  ...
    for (int i = 0; i < LEDC_NBR_PATTERNS; ++i)
    {
        qs = QString::fromStdString(ledPatternText[i]);
        qsl << qs;
    }
    m_ledPatternModel = new QStringListModel(qsl, this);

and widget.cpp:

    ui->comboBoxLedPattern->setModel(d->getLedPatternModel());
    mapper->addMapping(ui->comboBoxLedPattern, MODEL_COL_LED_PATTERN, "currentIndex");

I'm still missing something, though...no change in program behavior.

mzimmers

OK, I think I have it working now. Here's the program flow.

the worker object receives a message from a connected device, and converts the message from XML into a C data structure. The value for the LED pattern combo box is stored as an int from 0 to 3 within this struct:

DeviceDetails d;
string s;
...
 s = msg.getValue(msgTags[TAGENUM_LEDPATTERN]);
    d.ledPattern = ledPatternHash.at(s);

A signal is sent to the model.

the model sets the value onto the proper column:

    rc = m_model->setData(m_model->index(row, MODEL_COL_LED_PATTERN), d.ledPattern);

This is the step I was missing.

the display widget updates the combo box that represents this value because of this code:

    ui->comboBoxLedPattern->setModel(d->getLedPatternModel());
    mapper->addMapping(ui->comboBoxLedPattern, MODEL_COL_LED_PATTERN, "currentIndex");

The examples are excellent, but can be a little confusing because, in the interest of brevity, they embed the model in the widget code. It took me a little time to find this missing piece.

mzimmers

One remaining issue: the display doesn't update to reflect a remote change to the combo box, until the user does something (seemingly anything).

I think I've run into this before, a long time ago, but I don't remember what the fix is.

EDIT:

BTT. Anyone have any ideas?

mzimmers

I just discovered an issue-- while my QTableView properly displays multiple entries, my mapping to the combo box is only displaying one entry (the first one entered into the model). If I select a different entry from the table, the combo box is updated, but it doesn't display anything other than the selected entry.

Do I need to do something besides the standard mapping?

    mapper = new QDataWidgetMapper(this);
    mapper->setModel(d->getModel());
   ...
    mapper->addMapping(ui->comboBoxMacAddr, MODEL_COL_MACADDR);
    mapper->addMapping(ui->comboBoxLedPattern, MODEL_COL_LED_PATTERN, "currentIndex");

mzimmers

I never got this fixed, but I decided that having two places to select the MAC address was a bad idea anyway, so I replaced the QComboBox with a QLineEdit. Added this line to my main widget:

    mapper->addMapping(ui->lineEditMacAddr, MODEL_COL_MACADDR);

And it seems to work fine. Marking as solved...