[Qt-interest] [Qt-qml] hasChildren attribute for Qml Model?

[Stephen Kelly]

Martin Jones wrote:

> I've added a hasModelChildren property to the delegate and a couple of
> helper functions to VisualDataModel:
> 
> - VisualDataModel::modelIndex(int) returns a QModelIndex which can be
> assigned to VisualDataModel::rootIndex
> - VisualDataModel::parentModelIndex() returns a QModelIndex which can be
> assigned to VisualDataModel::rootIndex

Nice. :)

> 
> which simplifies the previously mentioned example to:
> 
> // main.cpp
>  int main(int argc, char ** argv)
>  {
>      QApplication app(argc, argv);
>      QDeclarativeView view;
> 
>      QDirModel model;
>      view.rootContext()->setContextProperty("myModel", &model);
> 
>      view.setSource(QUrl("qrc:view.qml"));
>      view.show();
> 
>      return app.exec();
>  }
> 
>  #include "main.moc"
> 
> // view.qml
>  import Qt 4.7
> 
>  ListView {
>      id: view
>      width: 200
>      height: 200
>      model: VisualDataModel {
>          model: myModel
>          delegate: Component {
>              Rectangle {
>                  height: 25; width: 200
>                  Text { text: filePath }
>                  MouseArea {
>                      anchors.fill: parent;
>                      onClicked: if (hasModelChildren) view.model.rootIndex
>                      =
> view.model.modelIndex(index)
>                  }
>              }
>          }
>      }
>  }
> 
> 
> Martin.
> 
> On Tue, 20 Apr 2010 08:34:34 pm ext Stephen Kelly wrote:
>> Martin Jones wrote:
>> > On Tue, 20 Apr 2010 07:56:17 pm ext Stephen Kelly wrote:
>> >> Martin Jones wrote:
>> >> > On Mon, 19 Apr 2010 10:09:17 pm ext Stephen Kelly wrote:
>> >> >> In QTreeView, that's a [+] which you can click to expand.
>> >> > 
>> >> > You could add a Q_INVOKABLE method to your model to get the child
>> >> > count, similar to the setRoot() method in this example:
>> >> > 
>> >> > http://qt.nokia.com/doc/4.7-snapshot/qml-
>> 
>> visualdatamodel.html#rootIndex-
>> 
>> >> prop
>> >> 
>> >> 
>> >> 
>> >> Indeed, however, it gets complicated when an intermediate proxy model
>> >> filters out all the children.
>> >> 
>> >> That is common in my case because it is something like a filesystem
>> >> where on one side is the folder structure and on the other side is the
>> >> files in the selected folder. In the view that is showing only the
>> >> folder structure, hasChildren is true only if it has subfolders. Files
>> >> are already filtered out.
>> >> 
>> >> First I put a method similar to what you describe in the proxy
>> >> actually sent into the qml environment, but then when I added another
>> >> proxy I had to move the logic to that class. That's not a good
>> >> solution.
>> >> 
>> >> Currently I have an invokable method in a globally accessible
>> >> application object to figure out if the correct proxy hasChildren at a
>> >> particular row. The method will have to be updated if ever the
>> >> application changes. It's a bit too much magic for me, so the best
>> >> place for a solution is further down the stack in Qt.
>> > 
>> > We'll add something along the lines of a "hasChildren" property to the
>> > delegate.
>> 
>> Awesome, thanks.
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>