How to create dependency between 2 columns using combobox delegates in MVC

**Santosh Reddy** · 3rd March 2015, 07:30

How did you put combo boxes in table view, did you use setIndexWidget()?

uzairsaeed702 · 3rd March 2015, 08:09

Via combo box delegate class

inherited by "QStyledItemDelegate"

**Santosh Reddy** · 3rd March 2015, 08:37

So how is that you are doing? Painting the combo box from delegate and when clicked creating an editor for the item using delegate?

uzairsaeed702 · 3rd March 2015, 08:50

No, I am creating combo box in QWidget *ComboBoxDelegate::createEditor(QWidget *parent, const QStyleOptionViewItem & option , const QModelIndex &index ) const method while i can check the "QModelIndex &index" in prder to check the specific column. Everything is working fine but only problem is that i have to make some logic that when i change something in column 4 then respectively columns 5 combo box has to be changed also.

**Santosh Reddy** · 3rd March 2015, 08:56

When the column 4 QComboBox is edited and data is submitted to the model, the model internally (in setData()) has to adjust the data for the column 5 and emit dataChanged() signal for the column 5 model index.

uzairsaeed702 · 3rd March 2015, 09:18

Well i am setting the model via setData() by void ComboBoxDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const function but when i send the data to the model it was currently having the pointer of column 4 not column 5. QcomboBox is working

e.g. see below Model

Qt Code:

Switch view

bool TableModel::setData(const QModelIndex & index, const QVariant &value, int role)
{
	int row = index.row();
	int col = index.column();
	QMap<QString, QVariant> qMapPair = p_tagSimItems->getItemsMap().at(row);
 
	if(index.isValid() && role == Qt::EditRole)
	{
		switch(col) {
		case 0 :
			{
				qMapPair.insert("a",value.toString());
				p_tagSimItems->setItemMap(row,qMapPair);
				emit (dataChanged(index , index));
				return true;
			}
			break;
		case 1 :
			{
				qMapPair.insert("b",p_tagSimItems->isValidEnteredType(value.toString()));
				p_tagSimItems->setItemMap(row,qMapPair);
				emit (dataChanged(index , index));
				return true;
			}
			break;
		case 2 :
			{
				qMapPair.insert("c",value.toString().toUShort(0,10));
				p_tagSimItems->setItemMap(row,qMapPair);
				emit (dataChanged(index , index));
				return true;
			}
			break;
 
		case 3 :
			{      [B]// the problem is here when model receive the signal from delegate in column 4 then i have to change the column 5 also manually which seems not possible because model is on column 4 .[/B]
				if (value.toString().toUShort(0,10) < 256)
				{
					qMapPair.insert("d",value.toString().toUShort(0,10));
				}else
				{
					qMapPair.insert("d",0);
				}
				p_tagSimItems->setItemMap(row,qMapPair); 
				emit (dataChanged(index , index));
				return true;
			}
			break;
		case 4 :
			{
				if (value.toString().toUShort(0,10) < 256)
				{
					qMapPair.insert("e",value.toString().toUShort(0,10));
				}else
				{
					qMapPair.insert("e",0);
				}
				p_tagSimItems->setItemMap(row,qMapPair);
				emit (dataChanged(index , index));
				return true;
			}
			break;
		default :
			break;
		}
	}
	return false;
}

bool TableModel::setData(const QModelIndex & index, const QVariant &value, int role)
{
	int row = index.row();
	int col = index.column();
	QMap<QString, QVariant> qMapPair = p_tagSimItems->getItemsMap().at(row);

	if(index.isValid() && role == Qt::EditRole)
	{
		switch(col) {
		case 0 :
			{
				qMapPair.insert("a",value.toString());
				p_tagSimItems->setItemMap(row,qMapPair);
				emit (dataChanged(index , index));
				return true;
			}
			break;
		case 1 :
			{
				qMapPair.insert("b",p_tagSimItems->isValidEnteredType(value.toString()));
				p_tagSimItems->setItemMap(row,qMapPair);
				emit (dataChanged(index , index));
				return true;
			}
			break;
		case 2 :
			{
				qMapPair.insert("c",value.toString().toUShort(0,10));
				p_tagSimItems->setItemMap(row,qMapPair);
				emit (dataChanged(index , index));
				return true;
			}
			break;

		case 3 :
			{      [B]// the problem is here when model receive the signal from delegate in column 4 then i have to change the column 5 also manually which seems not possible because model is on column 4 .[/B]
				if (value.toString().toUShort(0,10) < 256)
				{
					qMapPair.insert("d",value.toString().toUShort(0,10));
				}else
				{
					qMapPair.insert("d",0);
				}
				p_tagSimItems->setItemMap(row,qMapPair); 
				emit (dataChanged(index , index));
				return true;
			}
			break;
		case 4 :
			{
				if (value.toString().toUShort(0,10) < 256)
				{
					qMapPair.insert("e",value.toString().toUShort(0,10));
				}else
				{
					qMapPair.insert("e",0);
				}
				p_tagSimItems->setItemMap(row,qMapPair);
				emit (dataChanged(index , index));
				return true;
			}
			break;
		default :
			break;
		}
	}
	return false;
}

To copy to clipboard, switch view to plain text mode

After this, model call the

Qt Code:

Switch view

void ComboBoxDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const

void ComboBoxDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const

To copy to clipboard, switch view to plain text mode

function in order to set the Index of the combo box.

**Santosh Reddy** · 3rd March 2015, 10:57

// the problem is here when model receive the signal from delegate in column 4 then i have to change the column 5 also manually which seems not possible because model is on column 4 .

When inside setData() for column 4, you could call setData for column 5, you just need to create a new index (by calling QAbstractItemModel::createIndex) for column 5 and then pass it to the setData();

uzairsaeed702 · 3rd March 2015, 12:20

Originally Posted by Santosh Reddy

When inside setData() for column 4, you could call setData for column 5, you just need to create a new index (by calling QAbstractItemModel::createIndex) for column 5 and then pass it to the setData();

Can you give me a example ?

**Santosh Reddy** · 3rd March 2015, 13:08

Here you go, run this code.

I used delegate (because I used standard model) but you could do the similar in the your custom model.

Qt Code:

Switch view

#include <QtWidgets>
 
class Delegate : public QStyledItemDelegate
{
public:
    explicit Delegate(QObject * parent = 0) : QStyledItemDelegate(parent) {}
 
    QWidget * createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const
    {
        QComboBox * widget = new QComboBox(parent);
 
        widget->addItems(index.data(Qt::UserRole+1).toStringList());
 
        return widget;
    }
 
    void setModelData(QWidget * editor, QAbstractItemModel * model, const QModelIndex & index) const
    {
        if(index.column() == 0)
        {
            QComboBox * widget = dynamic_cast<QComboBox *>(editor);
 
            if(widget)
            {
                QString country = widget->currentText();
 
                QVariant russia = QStringList() << "Moscow" << "Saint Petersburg" << "Novosibirsk" << "Yekaterinburg";
                QVariant canada = QStringList() << "Toronto"  << "Parliament Hill" << "Quebec" << "Montreal";
                QVariant china  = QStringList() << "Shanghai" << "Beijing" << "Chongqing" << "Hong Kong";
                QVariant states = QStringList() << "New York City" << "Los Angeles" << "Chicago" << "Houston";
 
                QModelIndex nextColumnIndex = model->index(index.row(), 1);
 
                if(country == "Russia")
                {
                    model->setData(nextColumnIndex, russia, Qt::UserRole+1);
                }
                else if(country == "Canada")
                {
                    model->setData(nextColumnIndex, canada, Qt::UserRole+1);
                }
                else if(country == "China")
                {
                    model->setData(nextColumnIndex, china, Qt::UserRole+1);
                }
                else if(country == "United States")
                {
                    model->setData(nextColumnIndex, states, Qt::UserRole+1);
                }
 
                model->setData(index, country);
                model->setData(nextColumnIndex, "Select City Again");
            }
            widget->addItems(index.data(Qt::UserRole+1).toStringList());
        }
        else
        {
            QStyledItemDelegate::setModelData(editor, model, index);
        }
    }
};
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    QTableView table;
    QStandardItemModel model(4, 2);
 
    for (int row = 0; row < 4; row++)
    {
        QStandardItem *item = new QStandardItem(QString("Select Country").arg(row).arg(0));
        item->setData(QStringList() << "Russia" << "Canada" << "China" << "United States",Qt::UserRole+1);
        model.setItem(row, 0, item);
 
        item = new QStandardItem(QString("Select City").arg(row).arg(1));
        item->setData(QStringList());
        model.setItem(row, 1, item);
    }
 
    table.setModel(&model);
    table.setItemDelegate(new Delegate(&model));
    table.show();
 
    return app.exec();
}

#include <QtWidgets>

class Delegate : public QStyledItemDelegate
{
public:
    explicit Delegate(QObject * parent = 0) : QStyledItemDelegate(parent) {}

    QWidget * createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const
    {
        QComboBox * widget = new QComboBox(parent);

        widget->addItems(index.data(Qt::UserRole+1).toStringList());

        return widget;
    }

    void setModelData(QWidget * editor, QAbstractItemModel * model, const QModelIndex & index) const
    {
        if(index.column() == 0)
        {
            QComboBox * widget = dynamic_cast<QComboBox *>(editor);

            if(widget)
            {
                QString country = widget->currentText();

                QVariant russia = QStringList() << "Moscow" << "Saint Petersburg" << "Novosibirsk" << "Yekaterinburg";
                QVariant canada = QStringList() << "Toronto"  << "Parliament Hill" << "Quebec" << "Montreal";
                QVariant china  = QStringList() << "Shanghai" << "Beijing" << "Chongqing" << "Hong Kong";
                QVariant states = QStringList() << "New York City" << "Los Angeles" << "Chicago" << "Houston";

                QModelIndex nextColumnIndex = model->index(index.row(), 1);

                if(country == "Russia")
                {
                    model->setData(nextColumnIndex, russia, Qt::UserRole+1);
                }
                else if(country == "Canada")
                {
                    model->setData(nextColumnIndex, canada, Qt::UserRole+1);
                }
                else if(country == "China")
                {
                    model->setData(nextColumnIndex, china, Qt::UserRole+1);
                }
                else if(country == "United States")
                {
                    model->setData(nextColumnIndex, states, Qt::UserRole+1);
                }

                model->setData(index, country);
                model->setData(nextColumnIndex, "Select City Again");
            }
            widget->addItems(index.data(Qt::UserRole+1).toStringList());
        }
        else
        {
            QStyledItemDelegate::setModelData(editor, model, index);
        }
    }
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QTableView table;
    QStandardItemModel model(4, 2);

    for (int row = 0; row < 4; row++)
    {
        QStandardItem *item = new QStandardItem(QString("Select Country").arg(row).arg(0));
        item->setData(QStringList() << "Russia" << "Canada" << "China" << "United States",Qt::UserRole+1);
        model.setItem(row, 0, item);

        item = new QStandardItem(QString("Select City").arg(row).arg(1));
        item->setData(QStringList());
        model.setItem(row, 1, item);
    }

    table.setModel(&model);
    table.setItemDelegate(new Delegate(&model));
    table.show();

    return app.exec();
}

To copy to clipboard, switch view to plain text mode

uzairsaeed702 · 4th March 2015, 12:31

Originally Posted by Santosh Reddy

Here you go, run this code.

I used delegate (because I used standard model) but you could do the similar in the your custom model.

Qt Code:

Switch view

QModelIndex nextColumnIndex = model->index(index.row(), 1);

QModelIndex nextColumnIndex = model->index(index.row(), 1);

To copy to clipboard, switch view to plain text mode

Santosh Reddy thanks alot for the code but in custom model its difficult to examine the problem .Your hint for AbstractItemModel::createIndex worked like charm !!! . I have just inserted two line of code in model and few lines of code in my delegate class and work done.

Qt Code:

Switch view

QModelIndex changeRequest =  createIndex(row,4);
setData(changeRequest ,Qt::EditRole);

QModelIndex changeRequest =  createIndex(row,4);
setData(changeRequest ,Qt::EditRole);

To copy to clipboard, switch view to plain text mode

Above was my modification ,

Thanks again Santosh

Problem Solved (Y)

Thread: How to create dependency between 2 columns using combobox delegates in MVC

Thread Tools

Search Thread

Display

Hybrid View

Re: How to create dependency between 2 columns using combobox delegates in MVC

Re: How to create dependency between 2 columns using combobox delegates in MVC

Re: How to create dependency between 2 columns using combobox delegates in MVC

Re: How to create dependency between 2 columns using combobox delegates in MVC

Re: How to create dependency between 2 columns using combobox delegates in MVC

Re: How to create dependency between 2 columns using combobox delegates in MVC

Re: How to create dependency between 2 columns using combobox delegates in MVC

Re: How to create dependency between 2 columns using combobox delegates in MVC

Re: How to create dependency between 2 columns using combobox delegates in MVC

The following user says thank you to Santosh Reddy for this useful post:

Re: How to create dependency between 2 columns using combobox delegates in MVC

Similar Threads

qmake: create a dependency to an arbitrary file.

How to create a color bar in combobox ?

How to create a ComboBox which adds data dynamically into its DropDown list

ComboBox with multiple columns

Different delegates to different Columns of QTableView.

Tags for this Thread

Bookmarks

Bookmarks

Posting Permissions