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  1. Qt
  2. QTBUG-45500

QQuickListView keeps delegates around until next layout phase after model items have been removed

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    • Shovelling Snow, Q1/2020 Finale, Q2/2020 kick off

      I implement a QAbstractItemModel subclass which returns QObject* a instance with properties.

      I implement QML code to consume the properties from the instance:

          ListView {
        delegate: Item {
            id: deleg
            property var obj: model.instance
                Text {
                    text: deleg.obj.name
                }
                // ...

      I implement a method to delete an item.

              beginRemoveRows(QModelIndex(), i, i);
        m_instances.at(i)->deleteLater();
        m_instances.removeAt(i);
        endRemoveRows();

      When it is invoked I get warnings from QML

      main.qml:29: TypeError: Cannot read property 'colorName' of null
main.qml:24: TypeError: Cannot read property 'name' of null

      It seems that QML evaluates bindings in delegates whose model rows have already been deleted. It should probably not do that.

      Small testcase attached

        1. BindingIssue.zip
          2 kB
        2. testcase.zip
          2 kB
        For Gerrit Dashboard: QTBUG-45500
        # Subject Branch Project Status CR V
        553541,1 WIP: invalidate delegates which are about to be removed dev qt/qtdeclarative Status: NEW -2 0

            axelspoerl Axel Spoerl
            ske Steve
            Votes:
            34 Vote for this issue
            Watchers:
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              Created:
              Updated:
              Resolved:

                There is 1 open Gerrit change