QAbstractTableModel construction

jss193

Hello I have a doubt with this class,
when I create the following class:
header file:

#ifndef MYMODEL_H
#define MYMODEL_H

#include <QAbstractTableModel>
class MyModel : public QAbstractTableModel
{
    Q_OBJECT
public:
    MyModel(QObject *parent);
    int rowCount(const QModelIndex &parent = QModelIndex())const override;
    int columnCount(const QModelIndex &parent = QModelIndex())const override;
    QVariant data(const QModelIndex &index,int role = Qt::DisplayRole) const override;
    QVariant headerData(int section, Qt::Orientation orientation, int role)const;


};

#endif // MYMODEL_H

implementation

#include "mymodel.h"

MyModel::MyModel(QObject *parent):QAbstractTableModel(parent)
{

}
int MyModel::rowCount(const QModelIndex &parent) const{
    return 2;
}

int MyModel::columnCount(const QModelIndex &parent)const{
    return 3;
}

QVariant MyModel::data(const QModelIndex &index,int role)const{
    if (role == Qt::DisplayRole)
        {
           return QString("Row%1, Column%2")
                       .arg(index.row() + 1)
                       .arg(index.column() +1);
        }


    return QVariant();
}
QVariant MyModel::headerData(int section, Qt::Orientation orientation, int role) const
{
    if (role == Qt::DisplayRole)
    {
        if (orientation == Qt::Horizontal) {
            switch (section)
            {
            case 0:
                return QString("first");
            case 1:
                return QString("second");
            case 2:
                return QString("third");
            }
        }
    }
    return QVariant();
}

Main

#include "mainwindow.h"
#include <QApplication>
#include <QTableView>
#include "mymodel.h"
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QTableView tableView;
    MyModel myModel(0);
    tableView.setModel(&myModel);

    tableView.show();
    MainWindow w;
    w.show();

    return a.exec();
}

Why if I dont call methods from mymodel such as QVariant data, does it create the object returned by them? do not should it be included in constructor to be build?

Thank you!

SGaist

Hi,

What object are you talking about ? In your data re-implementation you either return a QString or an empty QVariant.

jss193

Im talking about QTableView object, build by setting myModel memory address
why it builds objects returned by methods data, headerdata,rowCount and columnCount if i dont call these methods?

SGaist

Because tableView calls them as part of its functionality.