QAbstractItemModel segmentation fault in QTreeView

[naturalpsychic]

Hello everyone, I have following code and its connected to treeview that does load item correctly

#include "listmodel.h"
 
ListModel::ListModel(QObject *parent) :
    QAbstractItemModel(parent)
{
    _data=new QList<MyClass*>();
 
    _data->append(new MyClass("first item"));
    _data->append(new MyClass("second item"));
 
 
}
int ListModel::rowCount(const QModelIndex &parent) const
{
    return _data->count();
 
}
int ListModel::columnCount(const QModelIndex &parent) const
{
    return 3;
 
}
QModelIndex ListModel::parent(const QModelIndex &child) const
{
     return QModelIndex();
}
bool ListModel::insertRows(int position,int row,MyClass cls, const QModelIndex &parent){
    beginInsertRows(parent,position,position+row-1);
    for(int r=0;r<row;r++)
    {
 
    this->_data->insert(position,&cls);
   }
    endInsertRows();
    return true;
 
}
QModelIndex ListModel::index(int row, int column, const QModelIndex &parent) const
{
    if (column < 0 || column >= 4 || row < 0 || parent.column() > 0)
           return QModelIndex();
 
 
       return createIndex(row, column, 0);
}
 
QVariant ListModel::headerData(int section, Qt::Orientation orientation, int role) const
{
    if (role != Qt::DisplayRole)
        return QVariant();
 
    if (orientation == Qt::Horizontal) {
        switch (section) {
        case 0:
            return tr("FileName");
 
        case 1:
            return tr("Dest");
 
        case 2:
            return tr("Dest Name");
 
        default:
            return QVariant();
        }
    }
    return QVariant();
}
QVariant ListModel::data(const QModelIndex &index, int role) const
{
   //if (index.row() < 0 || index.row() >=3)
              // return QVariant();
 
            switch( role )
            {
            case Qt::DisplayRole:
            {
                if (index.column() == 0)
                            return _data->at(index.row())->firstCol;
                else if (index.column() == 1)
                    return _data->at(index.row())->secondCol;
                else if (index.column() == 2)
                            return _data->at(index.row())->thirdCol;
            }
            case Qt::EditRole:
                {
 
                if (index.column() == 0)
                            return _data->at(index.row())->firstCol;
                else if (index.column() == 1)
                    return _data->at(index.row())->secondCol;
                else if (index.column() == 2)
                            return _data->at(index.row())->thirdCol;
 
                }
            default:
                return QVariant();
            }
}

#include "listmodel.h"

ListModel::ListModel(QObject *parent) :
    QAbstractItemModel(parent)
{
    _data=new QList<MyClass*>();

    _data->append(new MyClass("first item"));
    _data->append(new MyClass("second item"));


}
int ListModel::rowCount(const QModelIndex &parent) const
{
    return _data->count();

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

}
QModelIndex ListModel::parent(const QModelIndex &child) const
{
     return QModelIndex();
}
bool ListModel::insertRows(int position,int row,MyClass cls, const QModelIndex &parent){
    beginInsertRows(parent,position,position+row-1);
    for(int r=0;r<row;r++)
    {

    this->_data->insert(position,&cls);
   }
    endInsertRows();
    return true;

}
QModelIndex ListModel::index(int row, int column, const QModelIndex &parent) const
{
    if (column < 0 || column >= 4 || row < 0 || parent.column() > 0)
           return QModelIndex();


       return createIndex(row, column, 0);
}

QVariant ListModel::headerData(int section, Qt::Orientation orientation, int role) const
{
    if (role != Qt::DisplayRole)
        return QVariant();

    if (orientation == Qt::Horizontal) {
        switch (section) {
        case 0:
            return tr("FileName");

        case 1:
            return tr("Dest");

        case 2:
            return tr("Dest Name");

        default:
            return QVariant();
        }
    }
    return QVariant();
}
QVariant ListModel::data(const QModelIndex &index, int role) const
{
   //if (index.row() < 0 || index.row() >=3)
              // return QVariant();

            switch( role )
            {
            case Qt::DisplayRole:
            {
                if (index.column() == 0)
                            return _data->at(index.row())->firstCol;
                else if (index.column() == 1)
                    return _data->at(index.row())->secondCol;
                else if (index.column() == 2)
                            return _data->at(index.row())->thirdCol;
            }
            case Qt::EditRole:
                {

                if (index.column() == 0)
                            return _data->at(index.row())->firstCol;
                else if (index.column() == 1)
                    return _data->at(index.row())->secondCol;
                else if (index.column() == 2)
                            return _data->at(index.row())->thirdCol;

                }
            default:
                return QVariant();
            }
}

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But the problem is when i click ">" in treeview, it gives me segmentatioin fault error, while i am not even expecting it to have any children.

Please have a look at screenshot for display

[Santosh Reddy]

All the Model-View Interface Implmentations should check for QModelIndex ::isValid() condition and handle it accordingly (safely)

Example:

int ListModel::rowCount(const QModelIndex &parent) const
{
    if(parent.isValid())
        return _data->count(); //root node
    else
        return 0;
}

int ListModel::rowCount(const QModelIndex &parent) const
{
    if(parent.isValid())
        return _data->count(); //root node
    else
        return 0;
}

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