App crashing on addRow to QStandardItemModel

[homerun4711]

Hi!

I try to add values from a map to a QStandardItemModel, but my application is crashing. I have no idea why..

The last debug output is

QStandardItemModel::invisibleRootItem() const

The code is

QMap<QString, QString> map;
QMapIterator<QString, QString> i(map);
QList<QStandardItem*> rowList;
QStandardItemModel* test;
QStandardItem *item = test->invisibleRootItem();
 
 
     while (i.hasNext()) {
         i.next();
         rowList << new QStandardItem(i.value());
         }
 
        item->appendRow(rowList);

QMap<QString, QString> map;
QMapIterator<QString, QString> i(map);
QList<QStandardItem*> rowList;
QStandardItemModel* test;
QStandardItem *item = test->invisibleRootItem();


     while (i.hasNext()) {
         i.next();
         rowList << new QStandardItem(i.value());
         }

        item->appendRow(rowList);

To copy to clipboard, switch view to plain text mode 

Can you tell me why this happens?

Kind regards,
HomeR

[high_flyer]

You are defining 'test' pointer, but not initializing it, but you call invisibleRootItem() on it - no wonder it crashed!

QStandardItemModel* test; //<<-- not initialized
QStandardItem *item = test->invisibleRootItem(); //crash!

QStandardItemModel* test; //<<-- not initialized
QStandardItem *item = test->invisibleRootItem(); //crash!

To copy to clipboard, switch view to plain text mode 

[homerun4711]

You are right.
Sometimes I am dumb and blind

[homerun4711]

Hm, there is something else going wrong...could you please have a look into the code? I initialized the pointer but the application is still crashing at the same spot.

mainwindow.h

QStandardItemModel *model_customer;

QStandardItemModel *model_customer;

To copy to clipboard, switch view to plain text mode 

mainwindow.cpp

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    ...
    setupModels();
    ...
}
 
void MainWindow::setupModels()
{
 
 
    QStandardItemModel *model_customer = new QStandardItemModel;
 
}
 
void MainWindow::newcustomer() //called with a QPushButton
{
 
     AddressNew *newcustomer = new AddressNew(this);
      if (newcustomer->exec()) 
     {
     newcustomer->addToModel(model_customer);
     }

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    ...
    setupModels();
    ...
}

void MainWindow::setupModels()
{

    
    QStandardItemModel *model_customer = new QStandardItemModel;
   
}

void MainWindow::newcustomer() //called with a QPushButton
{

     AddressNew *newcustomer = new AddressNew(this);
      if (newcustomer->exec()) 
     {
     newcustomer->addToModel(model_customer);
     }

To copy to clipboard, switch view to plain text mode 

AddressNew.h

void setMap(QStandardItemModel* model);

void setMap(QStandardItemModel* model);

To copy to clipboard, switch view to plain text mode 

AddressNew.cpp

void AddressNew::setMap(QStandardItemModel* model)
 
QMap<QString, QString> map; //contains QStrings from QLineEdits
QMapIterator<QString, QString> i(map);
QList<QStandardItem*> rowList;
QStandardItemModel* test =  new QStandardItemModel;
QStandardItem *item = model->invisibleRootItem();
 
 while (i.hasNext()) {
         i.next();
         rowList << new QStandardItem(i.value());
         }
 
 item->appendRow(rowList);

void AddressNew::setMap(QStandardItemModel* model)

QMap<QString, QString> map; //contains QStrings from QLineEdits
QMapIterator<QString, QString> i(map);
QList<QStandardItem*> rowList;
QStandardItemModel* test =  new QStandardItemModel;
QStandardItem *item = model->invisibleRootItem();

 while (i.hasNext()) {
         i.next();
         rowList << new QStandardItem(i.value());
         }

 item->appendRow(rowList);

To copy to clipboard, switch view to plain text mode 

Any ideas?

[nroberts]

void AddressNew::setMap(QStandardItemModel* model)
 
QMap<QString, QString> map; //contains QStrings from QLineEdits
QMapIterator<QString, QString> i(map);
QList<QStandardItem*> rowList;
QStandardItemModel* test =  new QStandardItemModel;
QStandardItem *item = model->invisibleRootItem();

void AddressNew::setMap(QStandardItemModel* model)

QMap<QString, QString> map; //contains QStrings from QLineEdits
QMapIterator<QString, QString> i(map);
QList<QStandardItem*> rowList;
QStandardItemModel* test =  new QStandardItemModel;
QStandardItem *item = model->invisibleRootItem();

To copy to clipboard, switch view to plain text mode 

Well, now you've changed from getting the root item from 'test' to getting it from 'model', which is a parameter; 'test' now not being used. The problem is probably in calling code, which you haven't provided. May very well be exactly the same problem as before: invalid pointer.

[homerun4711]

Well, I tried to add the row to the model using

model->appendRow(rowList);

model->appendRow(rowList);

To copy to clipboard, switch view to plain text mode 

instead of

item->appendRow(rowList);

item->appendRow(rowList);

To copy to clipboard, switch view to plain text mode 

but the application is crashing anyway...

I tried to stick to code I found here (see 3.1 TreeView)

http://doc.troll.no/master-snapshot/modelview.html

standardModel = new QStandardItemModel ;
QList<QStandardItem *> preparedRow =prepareRow("first", "second", "third");
QStandardItem *item = standardModel->invisibleRootItem();
// adding a row to the invisible root item produces a root element
item->appendRow(preparedRow);

standardModel = new QStandardItemModel ;
QList<QStandardItem *> preparedRow =prepareRow("first", "second", "third");
QStandardItem *item = standardModel->invisibleRootItem();
// adding a row to the invisible root item produces a root element
item->appendRow(preparedRow);

To copy to clipboard, switch view to plain text mode 

[nroberts]

Well, I tried to add the row to the model using

model->appendRow(rowList);

model->appendRow(rowList);

To copy to clipboard, switch view to plain text mode 

instead of

item->appendRow(rowList);

item->appendRow(rowList);

To copy to clipboard, switch view to plain text mode 

but the application is crashing anyway...

Which leads me to believe I'm probably right and the problem is that 'model' is not initialized to mean anything. We can't tell for sure at this point though because the code that would be responsible for creating it, whatever is calling your AddressNew::setMap function, is not part of the code you provided in your question.

Edit:

Nevermind.... I'm wrong. You did provide that code; I just didn't see it. Your symptoms would lead me to believe I'm right but unless something is coming along and hosing your model_customer or something I'm not. You might just break in that function and make sure *model is something valid just to be sure though.

[homerun4711]

Ok, we are getting closer You are right, maybe the pointer is not
initialized when it is needed.
AddressNew::setMap is called (AddressNew is a QDialog) when the Dialog is
accepted.

AddressNew *newcustomer = new AddressNew(this);
 
  if (newcustomer->exec())
      {
       newcustomer->setMap(model_customer);
     }

AddressNew *newcustomer = new AddressNew(this);

  if (newcustomer->exec())
      {
       newcustomer->setMap(model_customer);
     }

To copy to clipboard, switch view to plain text mode 

[nroberts]

Ok, we are getting closer You are right, maybe the pointer is not
initialized when it is needed.
AddressNew::setMap is called (AddressNew is a QDialog) when the Dialog is
accepted.

AddressNew *newcustomer = new AddressNew(this);
 
  if (newcustomer->exec())
      {
       newcustomer->setMap(model_customer);
     }

AddressNew *newcustomer = new AddressNew(this);

  if (newcustomer->exec())
      {
       newcustomer->setMap(model_customer);
     }

To copy to clipboard, switch view to plain text mode 

Oh shit, I know where your problem is. Should have seen it before.

See your second cry for help post: http://www.qtcentre.org/threads/3736...700#post171700

In the first code segment you create an apparently global model_customer variable. Even if it's not global but is part of the class definition, the problem is still the same: name resolution applied to scoping rules.

Later, in setupModels() you do what kind of looks like an initialization of that variable, but it isn't. Because you provide the type before the variable name (QStandardItemModel*) you are actually declaring a new variable within a smaller scope, overriding the former. Thus the former, global version is never initialized and the pointer you DO initialize silently goes away, creating a memory leak BTW. Then when you call setMap you pass the former, global, uninitialized variable.

To fix your code, change this:

void MainWindow::setupModels()
{
 
 
    QStandardItemModel *model_customer = new QStandardItemModel;
 
}

void MainWindow::setupModels()
{

    
    QStandardItemModel *model_customer = new QStandardItemModel;
   
}

To copy to clipboard, switch view to plain text mode 

To this:

void MainWindow::setupModels()
{
 
 
    model_customer = new QStandardItemModel;
 
}

void MainWindow::setupModels()
{

    
    model_customer = new QStandardItemModel;
   
}

To copy to clipboard, switch view to plain text mode 

[homerun4711]

Oh my god, you are SO right!!!
Thank you very much! Exactly this was the problem.
So much to learn...