c++ - How to get QModelIndex to insert a new row in a QAbstractTableModel? -

i using model/view programming first time, using table view along qabstracttablemodel , qstyleditemdelegate need combo boxes. model:

class stablemodel : public qabstracttablemodel {    q_object     public:     stablemodel(int rows = 1, int columns = 1, qobject *parent = 0);      int rowcount(const qmodelindex &parent = qmodelindex()) const;     int columncount(const qmodelindex &parent = qmodelindex()) const;     qvariant data(const qmodelindex &index, int role) const;     qvariant headerdata(int section, qt::orientation orientation,                     int role = qt::displayrole) const;      qt::itemflags flags(const qmodelindex &index) const;     bool setdata(const qmodelindex &index, const qvariant &value,          int role = qt::editrole);      bool insertrows(int position, int rows, const qmodelindex &parent = qmodelindex());     bool insertcolumns(int position, int columns, const qmodelindex &parent = qmodelindex());     bool removerows(int position, int rows, const qmodelindex &parent = qmodelindex());     bool removecolumns(int position, int columns, const qmodelindex &parent = qmodelindex());     private:     qlist<qstringlist> rowlist;     comboboxitemdelegate *mydelegate; };     

here trying add new row in model , application crashing, think crashing because of invalid index.

   stablemodel *model; = new stablemodel(1, 1, this);    qmodelindex index = model->index(1, 1, qmodelindex());    model->insertrows(1, 4, index); 

how can correct index here or guide me add row using approach. thanks

edit:

bool stablemodel::insertrows(int position, int rows, const qmodelindex &parent) {     int columns = columncount();     begininsertrows(parent, position, position + rows - 1);      (int row = 0; row < rows; ++row) {         qstringlist items;         (int column = 0; column < columns; ++column)             items.append("");         rowlist.insert(position, items);     }      endinsertrows();     return true; } 

the model->index(1, 1, qmodelindex()); returns invalid index because there no index coordinates [1, 1].
can remove line, don't need parent index table.

with provided information, can't why index() method crashes. shouldn't, if invalid row , column number provided.