Hi, I'm currently writing an application using Qt5 (C++ and QML). It will get a big data backend in C++ which will get updated by different hardware in realtime.
To get this data displayed in QtQuick. I found the QObjectListModel approach which was presented on QtDD12: http://qt-project.org/videos/watch/qml-for-desktop-apps I've updated the QObjectListModel implementation to work with Qt5. The application I've written sometimes crashes. It seems that this has to to with the QObjectListModel approach. I've put together a simple example to show this issue. A simple git import from QtCreator should make it very simple for you to test my example application. Clone URL: https://railwayco...@bitbucket.org/railwaycoder/qobjectlistmodelqmltesting.git QObjectListModel is created in C++ and filled with 200 TestOBjects. The OBjectListModel is than exposed to QML using rootContext->setContextProperty(...) In Qml there is a simple ListView filled with data from the QObjectListModel childs. At this point there are no problems. But I want to do some actions with the TestObject selected in the ListView. Therefore I added the following code: onCurrentIndexChanged: { console.log(currentIndex) console.log(ObjectListModel.get(currentIndex)) } First testing looks also okay. But if you do fast scrolling up and down using keyboard or sometimes by simply selecting an item by mouse, the application crashes with following error: qml: TestObject(0x12e1820) qml: 51 qml: TestObject(0x12e1610) qrc:/main.qml:35: TypeError: Cannot reat property 'name' of null qml: 50 The program has unexpectedly finished. My idea about this issue is, that this has something to do with the seperate QtQuick rendering thread in Qt5. ListView sometimes needs to update it's data from the model and it seems if in the same moment ObjectListModel.get(currentIndex) is called this issue happens. Maybe I am completly wrong and there is a simple mistake in my code? Otherwise is this a bug? Or is it my task to take care of the QML rendering thread? Is QOBjectListModel approach best practise for accessing big data which is asynchronylsy updated by C++? Best Regards, railwaycoder
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