Hello,
Thank you for your reply. I will have to think about the best way to make this
work within the program. I am still confused a bit.
Currently, the user has buttons and context menus to create the custom items in
the list view. This is nice for them because they can easily see the changes.
When the user is done arranging and creating items in the list widget, then the
program stores the items (which are all custom objects derived from the
QListWidgetItem) into a Python list for storage. It looks like this:
for N in range( ListWidget.count() ): self.Positions.append( ListWidget.item(N)
)
Then the list widget is cleared after the items are stored to a Python list.
But - if I print the items from the Python list they are all still there as
expected. If I look at the type() of the items in the list they are all the
custom types (also as expected). But if the program takes an item from the
Python list and adds it to the list widget I get the error. It seems that the
objects were stored correctly, but obviously not completely.
So the items are stored before the list widget is cleared - I think this is
what you were showing in your example. But it is done "at the end" instead of
right away. I still feel that I am doing something else wrong.
Henry
On Wednesday, February 8, 2023 at 05:16:03 PM MST, Boštjan Mejak
<bostjan.xpe...@gmail.com> wrote:
Hello, Henry,
let me brighten your day, if I may.
It seems that the issue lies in the fact that you are trying to add an object
to the list widget after it has already been deleted. When the list widget is
cleared using the .clear() method, the objects contained in the list are
deleted, which means that any references to those objects will no longer be
valid.
To avoid this issue, you can store the data in a separate list and add the
items to the list widget after it has been cleared. For example, you could
define a positions list and store the RobotPosition objects in it, then clear
the list widget and add the items from the positions list.
Let me give you an example.
---positions = []
Position = ConfigurationClasses.RobotPosition()
Position.setType('Intermediate')
Position.setName('Position')
Position.updateTooltip()
positions.append(Position)
self.ui.listRobotPathPositions.clear()
for position in positions:
self.ui.listRobotPathPositions.addItem(position)---
This way, the objects will not be deleted until the positions list goes out of
scope, or is explicitly deleted. I hope this solves your problem.
On Thu, Feb 9, 2023 at 12:53 AM henry.wede--- via PySide
<pyside@qt-project.org> wrote:
Hello,
I am trying to track down a " Internal C++ object (RobotPosition) already
deleted" error. The Internet says that my object is being garbage collected
because it falls out of scope. This is part of a big application so I can't
just post a folder of code, but please let me try to explain what I think the
problem is.
I have an object that is defined like this:
class RobotPosition(QtWidgets.QListWidgetItem): '''Class for storing a
single robot position. '''
def __init__(self):
super().__init__()
{snip}
def __str__(self):
{snip}
def setType(self, Type):
{snip}
def setName(self, NewName):
{snip}
def updateTooltip(self):
{snip}
Theses objects are created (as shown below) and added to a list widget.
{snip}Position =
ConfigurationClasses.RobotPosition()Position.setType('Intermediate')Position.setName('Position')Position.updateTooltip()
self.ui.listRobotPathPositions.addItem(Position)print(Position.parent())
{snip}
The objects display without any issues with the addItem method of the list
widget.
The application stores different lists of these objects and uses the same list
widget to display them. If I print these list of objects, they all print
nicely due to the __str__ method. So far, so good.
But when the list widget is cleared (using .clear() ) and the application tries
to add a list of objects back to the list widget this message shows up:Internal
C++ object (RobotPosition) already deleted
I added the 'print(Position.parent()) ' command above and it says
that:AttributeError: 'RobotPosition' object has no attribute 'parent'
So... I think this is the heart of my problem. Python ( or Qt?) thinks my
RobotPosition object has no parent. However, I think that it does have a
parent because it is derived from a QListWidgetItem object that has a parent.
Could someone please shed some light on what I am doing wrong?
Thanks in advance,Henry
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