How to add one empty row in ComboBox with model

[TomASS]

Hi again

I've a ComboBox fill by QSqlQueryModel:

ComboKierowcy = new QComboBox(parent);
  QSqlQueryModel *ComboKierowcyModel = new QSqlQueryModel();
 
  ComboKierowcyModel->setQuery( "SELECT * FROM kierowcy ORDER BY Nazwisko" );
  if (ComboKierowcyModel->lastError().isValid())
    qDebug() << ComboKierowcyModel->lastError();
 
  QModelIndex tmp;
  ComboKierowcy->setModel(ComboKierowcyModel);
  ComboKierowcy->setModelColumn(1);

ComboKierowcy = new QComboBox(parent);
  QSqlQueryModel *ComboKierowcyModel = new QSqlQueryModel();

  ComboKierowcyModel->setQuery( "SELECT * FROM kierowcy ORDER BY Nazwisko" );
  if (ComboKierowcyModel->lastError().isValid())
    qDebug() << ComboKierowcyModel->lastError();

  QModelIndex tmp;
  ComboKierowcy->setModel(ComboKierowcyModel);
  ComboKierowcy->setModelColumn(1);

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Everything is ok, but I need a one empty position on the first place. How add this?

[victor.fernandez]

You will have to subclass QSqlQueryModel and reimplement data() and rowCount() and perhaps some more methods. You can do something like this:

In myquerymodel.h file:

#include <QSqlQueryModel>
 
class MyQueryModel : public QSqlQueryModel
{
    Q_OBJECT
 
public:
    MyQueryModel(QObject *parent = 0);
 
    virtual QVariant data(const QModelIndex& item, int role = Qt::DisplayRole) const;
    virtual int rowCount(const QModelIndex& parent = QModelIndex()) const;
};

#include <QSqlQueryModel>

class MyQueryModel : public QSqlQueryModel
{
    Q_OBJECT

public:
    MyQueryModel(QObject *parent = 0);

    virtual QVariant data(const QModelIndex& item, int role = Qt::DisplayRole) const;
    virtual int rowCount(const QModelIndex& parent = QModelIndex()) const;
};

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In the myquerymodel.cpp file:

MyQueryModel::MyQueryModel(QObject *parent) : QSqlQueryModel(parent)
{
}
 
QVariant MyQueryModel::data(const QModelIndex& item, int role) const
{
    if(item.row() == 0)
        return QVariant();
 
    QModelIndex fakeItem = this->QSqlQueryModel::index(item.row()-1, item.column());
    return this->QSqlQueryModel::data(fakeItem, role);
}
 
int MyQueryModel::rowCount(const QModelIndex& parent) const
{
    return this->QSqlQueryModel::rowCount(parent) + 1;
}

MyQueryModel::MyQueryModel(QObject *parent) : QSqlQueryModel(parent)
{
}

QVariant MyQueryModel::data(const QModelIndex& item, int role) const
{
    if(item.row() == 0)
        return QVariant();

    QModelIndex fakeItem = this->QSqlQueryModel::index(item.row()-1, item.column());
    return this->QSqlQueryModel::data(fakeItem, role);
}

int MyQueryModel::rowCount(const QModelIndex& parent) const
{
    return this->QSqlQueryModel::rowCount(parent) + 1;
}

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