Qt - Hash table contains incorrect values - c++

Question

I'm doing my controller. When I click on an item in my ListWidget, the following method is called :
void ContactBookController::setCurrentlySelectedItem(QListWidgetItem *item)
{
setCurrentItem(*item);
m_window.setEditButtonsState(true);
}
And the setCurrentItem() method is as follows : (m_current_item is a private variable):
void ContactBookController::setCurrentItem(const QListWidgetItem &current_item)
{
m_current_item = current_item;
}
Now, when I create a contact, I add an item to the QListWidget, but I also create a Contact object, but I also bind them together in a QHash so I know what QListWidgetItem corresponds to what Contact. In short, here is what I did :
void ContactBookController::createContact()
{
auto new_contact = m_contact_book.createContact();
if(new_contact != nullptr)
{
new_contact->setName(tr("New contact"));
}
auto list_item = m_window.createContact(new_contact->getName());
m_window.clearSelection();
m_contact_map.insert(list_item, new_contact);
}
Now, when clicking on a QListWidgetItem, I activate the edit button and I would like to retrieve the corresponding Contact object. However, when doing this, the Contact object doesn't seem to be correct. Indeed, if I use a method on him (like getName()), my application instantly crashes.
Here is what I did :
void ContactBookController::editContact()
{
auto list_item = m_current_item;
auto contact = m_contact_map.value(&list_item); /* doesn't work */
}
My hash table is declared as such :
QHash<QListWidgetItem*, Contact*> m_contact_map;
Any idea what I did wrong ?

Answer 1

Your hash has the type QHash<QListWidgetItem*, Contact>. So, mapping a item pointer to a contact value.
When you save the mapping for a specific item with m_contact_map.insert(list_item, new_contact), you add a mapping from the item pointer to the contact. But when you try to retrieve the contact with m_contact_map.value(&list_item), you look up the value for the pointer to the local list_item variable, which points to somewhere on the stack, and has nothing to do with the pointer to the item that is shown in the view.
Either you need to save to pointer to the selected value, i.e. make m_current_item a QListWidgetItem *m_current_item, or you simply use QListWidget::currentItem() to retrieve the current item without the need for an additional member variable.
(Side note: You should check for currentItem() != nullptr, since a list widget does not necessarily has an item selected.)